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Assessing Readiness in Military Women: The Relationship of Body, Composition, Nutrition, and Health (1998)

Chapter: 6 Pregnancy and Lactation and Postpartum Return-To-Duty Fitness

« Previous: 5 Nutritional Concerns of Military Women
Suggested Citation:"6 Pregnancy and Lactation and Postpartum Return-To-Duty Fitness." Institute of Medicine. 1998. Assessing Readiness in Military Women: The Relationship of Body, Composition, Nutrition, and Health. Washington, DC: The National Academies Press. doi: 10.17226/6104.
×

6
Pregnancy and Lactation and Postpartum Return-to-Duty Fitness

Military Policies On Pregnancy And Postpartum Attainment Of Weight/Fat And Fitness Standards

Prior to 1972, active-duty women were separated involuntarily from the military if they became pregnant. In 1972, this policy was amended, and provision was made for exceptions to separation on an individual basis. In 1975, the discharge policy was abandoned following several challenges to its constitutionality. Today, pregnant women who wish to remain in the service may do so. Department of Defense (DoD) policy has been that separation from the service for pregnancy is an option and with minor exceptions, pregnant women cannot be involuntarily discharged. Enlisted women are not separated for pregnancy/childbirth unless it is in the best interest of the servicemember (Thomas and Thomas, 1992). Current military policies on pregnancy and the postpartum period are summarized in Table 6-1. Data on the marital and parental status of active-duty women are summarized in Tables 6-2 and 6-3. In general, pregnant servicewomen are considered nondeployable (Army) or restricted from certain work environments and duties (all services), and are removed from sea duty by the twentieth week of pregnancy (Navy, Marine Corps, and Coast Guard). Prior to the twentieth week, pregnant women are allowed to remain on sea duty if, in an emergency situation, medical treatment can be obtained within 6 hours (Navy and Marine Corps) or 3 hours (Coast Guard). Women are required to return to full duty after 6

Suggested Citation:"6 Pregnancy and Lactation and Postpartum Return-To-Duty Fitness." Institute of Medicine. 1998. Assessing Readiness in Military Women: The Relationship of Body, Composition, Nutrition, and Health. Washington, DC: The National Academies Press. doi: 10.17226/6104.
×

TABLE 6-1 U.S. Military Practices and Policies for Female Personnel: Pregnancy and Postpartum Periods

Period

Army

Navy

Air Force

Marine Corps

Coast Guard

Pregnancy

•Exempt from body composition, fitness testing (AR 40-501, 1995)

•Exempt from body composition, fitness testing

•Exempt from body composition, fitness testing

•Full-duty status and deployable until medical officer certifies that full duty is medically inadvisable

•Exempt from body composition testing

 

•Nondeployable

•20-wk Rule (no shipboard duty after 20th week of gestation)

•Restrictions based on work environment

•May not participate in contingency operations or be deployed for operations aboard Navy vessels

•>28 weeks, 40-h work week; no overseas duty

 

•At 20 weeks, standing at parade rest/attention < 15 minutes

•6-h Rule (medical evacuation for ER must be within 6 hours) (OPNAVINST 6000.1A, 1989)

•Pregnant members assigned to areas without obstetrical care will have assignment curtailed by 24th week (AFI 44-102, 1996)

•Flight personnel are grounded unless cleared by medical waiver

•Other duty restrictions based on work environment; no rescue swimmer duties

 

•At 28 weeks, 40-h week/8-h day

•40-h work week

 

•Excused from duties (physical training or standing in formation) that in the opinion of the medical officer are hazardous to her health or to her unborn child

•Not deployable during 20th week through 6 months postpartum

 

 

•Standing at parade rest/attention no more than 20 minutes

 

•Remains available for worldwide assignment

•Time to medical evacuation for emergencies < 3 hours

 

 

 

 

•Pregnant Marines stationed in Hawaii will not be detached after their 6th month; if overseas, they may be detached at their normal rotation tour date; if assigned to shipboard duty, the Marine will be reassigned at first opportunity and no later than the 20th week of pregnancy

•No flight duties after 2nd trimester

 

 

 

 

 

•Prenatal sick leave not to exceed 30 days

Suggested Citation:"6 Pregnancy and Lactation and Postpartum Return-To-Duty Fitness." Institute of Medicine. 1998. Assessing Readiness in Military Women: The Relationship of Body, Composition, Nutrition, and Health. Washington, DC: The National Academies Press. doi: 10.17226/6104.
×

Postpartum

•Return to duty at 6 weeks

•Return to duty at 6 weeks

•Return to duty at 6 weeks

•Return to duty at 6 weeks (or as soon after delivery as medical officer certifies)

For nursing mothers, the 6-mo weight standards exemption following delivery will begin at the conclusion of the nursing period, but no later than 12 months postdelivery

 

•Exempt from weigh-in until 6 months

•Exempt from weigh-in until 6 months

•Exempt from weigh-in until 6 months

•Exempt from weigh-in until 6 months

•Postdelivery maternity leave up to 6 weeks

 

•Physical training at own pace for 45 days

•Exempt from fitness testing for 6 months

•Deferment from deployment until 4 months postpartum

•Exempt from fitness testing for 6 months

•Not deployable until 6 months postpartum

 

•Exempt from fitness testing for 135 days (FM 21-20, 1992)

•Deferment from deployment until 4 months postpartum

•Exempt from fitness testing for 6 months (AFI 40-502, 1994)

•Deferment from deployment until 4 months postpartum

•Exempt from weight standards for up to 6 months

 

•Deferment from deployment until 4 months postpartum

•No policy regarding breastfeeding

•Commander may approve up to 18 months deferral

•(MCO 5000.12D, 1995)

 

 

•No policy regarding breastfeeding

 

•No policy regarding breastfeeding

•No policy regarding breastfeeding

 

NOTE: AR, Army Regulation; OPNAVINST, Naval Operations Instruction; AFI, Air Force Instruction; FM, Field Manual; MCO, Marine Corps Order. A more detailed table appears in Appendix B.

Suggested Citation:"6 Pregnancy and Lactation and Postpartum Return-To-Duty Fitness." Institute of Medicine. 1998. Assessing Readiness in Military Women: The Relationship of Body, Composition, Nutrition, and Health. Washington, DC: The National Academies Press. doi: 10.17226/6104.
×

TABLE 6-2 Percentage of Married U.S. Military Active-Duty Women by Rank and Service as of September 30, 1996

Rank/Age (years)

Army (%)

Navy (%)

Marine Corps (%)

Air Force (%)

Enlisted women

 

 

 

 

17–25

33

30

33

42

26–40

61

57

60

65

41–65

55

56

52

66

Warrant officers*

 

 

 

 

17–25

50

100

 

 

26–40

62

57

64

 

41–65

60

67

41

 

Officers

 

 

 

 

17–25

34

23

22

33

26–40

60

56

57

62

41–65

59

57

55

61

* The Air Force does not have personnel classified as warrant officers.

SOURCE: Defense Manpower Data Center (Rosslyn, Va., 1996).

TABLE 6-3 Parental Status of U.S. Military Active-Duty Women

 

Army (%)

Navy (%)

Marine Corps (%)

Air Force (%)

Enlisted women

 

 

 

 

Not a parent

58

69

75

67

Married parent

27

19

16

23

Single parent

15

12

9

9

Total parents*

42

31

25

32

Warrant officers

 

 

 

 

Not a parent

49

44

51

 

Married parent

36

40

32

 

Single parent

15

16

17

 

Total parents

51

56

49

 

Officers

 

 

 

 

Not a parent

69

73

83

70

Married parent

24

22

13

25

Single parent

6

5

3

5

Total parents

30

27

16

30

* Married and single.

The Air Force does not have personnel classified as warrant officers.

SOURCE: Defense Manpower Data Center (Rosslyn, Va., 1996).

Suggested Citation:"6 Pregnancy and Lactation and Postpartum Return-To-Duty Fitness." Institute of Medicine. 1998. Assessing Readiness in Military Women: The Relationship of Body, Composition, Nutrition, and Health. Washington, DC: The National Academies Press. doi: 10.17226/6104.
×

weeks postpartum unless on medical waiver, and must comply with weight standards by 6 months. Army women must comply with fitness standards by 135 days; women in the other services are allowed 180 days. According to DoD Directive 1315.7 (1991), women in all services are deployable after 4 months postpartum, unless they receive a medical waiver.

Profile Of Military Women And Risk Factors For Poor Pregnancy Outcome

Military service may involve a variety of factors that pose a risk to successful pregnancy outcome in active-duty women. These factors include the profile of the military women herself, dietary habits, pressures to meet body weight standards, and service work environments. For example, in a study that compared pregnant active-duty Navy women with civilian female Navy spouses, active-duty women were younger (22.5 vs. 23.5 years), more often single (33 vs. 6%), and less likely to have progressed beyond a high school education (50 vs. 70%). Active-duty women reported more prenatal visits (13.6 vs. 12.6) and less social support (Support Behaviors Inventory score of 101.85 vs. 109.37) (Messersmith-Heroman et al., 1994).

Nutritional surveys have revealed suboptimal iron and folate status among some military women, which poses a risk during pregnancy. A study conducted at Fort Jackson, South Carolina, indicated that 56 percent of the female Army soldiers at the beginning of basic combat training (BCT) had ferritin levels less than 20 ng/ml, although hemoglobin levels were normal. Many of these women were in marginal iron status and did not improve or actually worsened through basic training. Mean serum folate was in the low normal range and declined significantly over the 8-wk training period (Westphal et al., 1995).

Women who are thinner prior to pregnancy are at risk for giving birth to infants with lower birthweights (IOM, 1990). The prevalence of underweight (body mass index [BMI, weight in kilograms divided by the square of the height in meters] < 19.8) servicewomen was 14.5 percent for ages younger than 20 years, 11.3 percent for 20 to 25 years, 9.8 percent for 26 to 34 years, and 4.9 percent for 35 years or older (Personal communication, R. M. Bray, Research Triangle Park, N.C., 1996; see Table 6-4).

In addition, studies have shown adverse effects on pregnancy outcome of long work hours, heavy lifting, and chemical and infectious disease exposures (Keith and Luke, 1991; Mamelle et al., 1984). Premature birth has been associated with occupational fatigue factors such as prolonged standing and physical work. In a case control study of nurses (N = 210 cases and N = 1,260 controls), factors associated with preterm birth included hours worked per week, per shift, and while standing; noise; physical exertion; and occupational fatigue score (Luke et al., 1995). The adjusted odds ratios were 1.6 for hours worked per week (< 36 vs. > 36 h/wk), and 1.4 for fatigue score (< 3 vs. > 3).

Military women experience many of these work-related factors. Active-duty Navy women (N = 100) worked longer into pregnancy (37.27 vs. 32.74 weeks) and longer hours (39.18 vs. 36.12 h/wk), and reported lower levels of social support than did their civilian counterparts (N = 100) (Messersmith-Heroman et al., 1994). Until the third trimester, most pregnant Navy

Suggested Citation:"6 Pregnancy and Lactation and Postpartum Return-To-Duty Fitness." Institute of Medicine. 1998. Assessing Readiness in Military Women: The Relationship of Body, Composition, Nutrition, and Health. Washington, DC: The National Academies Press. doi: 10.17226/6104.
×

TABLE 6-4 Prevalence of Underweight as Determined by a Body Mass Index of Less Than 19.8 for U.S. Military Active-Duty Military Women

Characteristic

(N)

Prevalence

Service

 

 

Army

678

10.4 (1.5)

Navy

826

7.1 (0.9)

Marine Corps

569

12.6 (1.3)

Air Force

826

10.8 (1.1)

Age

 

 

<20

184

14.5 (3.8)

20–25

1,040

11.3 (1.2)

26–34

887

9.8 (1.0)

35+

788

4.9 (1.1)

Race/ethnicity

 

 

White

1,774

10.6 (0.9)

Black

680

7.6 (1.4)

Hispanic

251

11.9 (2.3)

Other

194

8.6 (2.0)

Rank

 

 

Enlisted

2,293

9.4 (0.8)

Officer

606

11.9 (1.6)

Total

2,899

9.8 (0.7)

NOTE: Prevalence estimates are percentages with standard errors in parentheses.

SOURCE: Survey of Health-Related Behaviors among Military Personnel (Personal communication, R. M. Bray, Research Triangle Park, N.C., 1996).

women (N = 486) worked normal shifts and hours in their assigned jobs (Thomas et al., 1991). There was some evidence that pregnant women would be transferred off ships before 20 weeks. Frequently mentioned hazards included toxic chemicals, fuels, fumes from paints, and other products. Less frequently mentioned hazards were noise, x rays, electric shock, and radiation.

The risk of radiation exposure of the fetus during high-altitude or space flight poses the single biggest medical concern in allowing women access to all aviation and space careers. Orthostatic intolerance during flight may contribute to lower gravitational tolerance during pregnancy. There is a chance of incapacitation due to spontaneous abortion, nausea and vomiting, weight gain, and unsteadiness. Spontaneous fetal loss was increased in flight attendants compared with the general population (relative risk, RR = 1.9) (Lyons, 1992).

Suggested Citation:"6 Pregnancy and Lactation and Postpartum Return-To-Duty Fitness." Institute of Medicine. 1998. Assessing Readiness in Military Women: The Relationship of Body, Composition, Nutrition, and Health. Washington, DC: The National Academies Press. doi: 10.17226/6104.
×

Summary

Women who become pregnant while serving on active duty may face a variety of factors that present a risk to the developing fetus as well as to themselves. These may include dietary habits that result in low iron or folate status; underweight or the pressure to meet body weight standards; young age; lack of social or spousal support; work-related factors such as prolonged standing, heavy lifting, and toxic exposures; and the likelihood that the pregnancy is unplanned.

Reproductive History Of Military Women

Pregnancy Prevalence

In fiscal year 1996, 13,423 active-duty women had a child by birth or adoption. Table 6-5 shows the distribution by rank and service.

Navy

Incidences of pregnancy and single parenthood were studied among 2,000 enlisted personnel in the Navy (Thomas and Edwards, 1989). Pregnancy rates of Navy women were similar to civilian age cohorts (13% on an annual basis), and pregnant women constituted 1.4 percent of enlisted forces. Pregnancy rates were highest among women in pay grades E-4 and below and among women in their first enlistment. Women on ships had a lower pregnancy rate than those assigned ashore. Surveys show that 60 percent of pregnancies were unplanned. Military medical facilities were used by 73 percent of women for their prenatal care. Probably as a consequence, the abortion and miscarriage/ stillbirth rates of Navy women were lower than those of civilians (abortions are not performed at military facilities). The proportion of single parents in the Navy (3% males and 14% females) is twice that of the civilian population. Single parenthood was more characteristic of personnel in their second and subsequent enlistments than among first termers. First-term retention of Navy women lags behind that of men by 5 percent, with pregnancy as a major cause of retention losses (Rowe, 1994). In subsequent enlistments, retention of women is higher than for men.

TABLE 6-5 Percentage of Active-Duty Women Who Had a Child in Fiscal Year 1996

Rank

Army (%)

Navy (%)

Marine Corps (%)

Air Force (%)

Enlisted

8

7

7

7

Warrant officers*

4

5

10

 

Commissioned officers

6

5

4

5

* The Air Force does not have personnel classified as warrant officers.

SOURCE: Defense Manpower Data Center (Rosslyn, Va., 1996).

Suggested Citation:"6 Pregnancy and Lactation and Postpartum Return-To-Duty Fitness." Institute of Medicine. 1998. Assessing Readiness in Military Women: The Relationship of Body, Composition, Nutrition, and Health. Washington, DC: The National Academies Press. doi: 10.17226/6104.
×

According to Thomas and Edwards (1989), policies regarding pregnancy were not well understood or enforced. Fewer than half of the male first-class and chief petty officers were correctly informed about Navy pregnancy policy, in particular, regulations affecting women in ships.

According to 1990 Bureau of Naval Personnel (BUPERS) records, 90 percent of the 50 Navy women discharged for pregnancy were in their first enlistment. The discharge rate was highest among those who were married to another military member and lowest among single women. Although pregnancy is a major reason for women to be discharged, pregnancy accounted for only 3.5 percent of all military discharges from the Navy in 1990. Fewer than 20 percent of supervisors thought that pregnant women had a negative effect on the workload of others.

A survey of psychosocial and behavioral correlates of pregnancy aboard Navy ships revealed that 4.2 percent of the 2,032 respondents were pregnant at the time of the survey; 30 percent were on sea duty when they became pregnant (Thomas, 1996). Only 27 percent of these pregnancies were planned, whereas 50 percent of pregnancies on shore were planned. Pregnant women were younger and more likely to be married than were nonpregnant sailors. Pregnancy rates were not related to education, race, or stress measures. Birth control was used by 59 percent of the sample. Of the remaining 41 percent, 14 percent were not sexually active, 13 percent were sterile, and 14 percent used no birth control method.

Marine Corps

Pregnancy rates in the Marine Corps are at levels either equal to or lower than rates in the general population (Flatter, 1996). Women's attrition rates have been decreasing steadily in the Marine Corps. Nevertheless, attrition for over 50 percent of all female (and 30% of males) Marines occurs for one reason or another before completion of their first enlistment. Pregnancy is a major contributor to this high attrition among women. In 1991, the pregnancy attrition rate for women was 13.2 percent (overall attrition = 54.1%). Unplanned pregnancies, which account for the majority of pregnancy attrition cases, are common. Despite military policy prohibiting abortion, the incidence of abortion among women in the Marine Corps is believed to be at least as high as that in the general population (Flatter, 1996).

Army

According to the Army Sample Survey of Military Personnel, 8 percent of enlisted females, 4 percent of warrant officers, and 6 percent of officers reported giving birth during fiscal year 1996 (Table 6-5).

Air Force

Prevalence rates of pregnancy among Air Force servicewomen were obtained from the Air Force Office of Medical Logistics. As of June 30, 1997, 5 percent of enlisted women and 3 percent of officers reported being pregnant. Enlisted women 20 to 24 years of age reported the

Suggested Citation:"6 Pregnancy and Lactation and Postpartum Return-To-Duty Fitness." Institute of Medicine. 1998. Assessing Readiness in Military Women: The Relationship of Body, Composition, Nutrition, and Health. Washington, DC: The National Academies Press. doi: 10.17226/6104.
×

highest pregnancy rate, just over 6 percent. During fiscal year 1996, 7 percent of enlisted women and 5 percent of officers reported giving birth (Table 6-5).

Civilians

Taking the most recent civilian data available (Ventura et al., 1997), the percentages of females in each age group who gave birth in 1996 were as follows: 8.7 percent of those aged 18 to 19 years; 11.1 percent of those aged 20 to 24 years; 11.4 percent of those aged 25 to 29 years; and 8.5 percent of those aged 30 to 34 years. Thus pregnancy rates for civilian women are significantly higher than for active-duty women at all ages.

Pregnancy Course And Outcome

Although DoD service-wide statistics are not available, studies suggest that pregnancy complications and preterm delivery may be more prevalent in military women than in their civilian counterparts.

A survey compared deliveries within the DoD military health care system in 1980 (N = 100,351) with deliveries in civilian hospitals (N = 3,762,000) (Horton et al., 1988). Compared with civilian hospitals, military hospitals had a higher percentage of Caucasian women (73 vs. 70%) in their twenties (72 vs. 64%) than did civilian hospitals. A lower proportion of deliveries in the military population were uncomplicated compared with the civilian (39 vs. 49%), regardless of age or race. However, the definition of uncomplicated delivery was rather restrictive in the military. In DoD hospitals, average stays compared with civilian hospitals were longer (3.3 vs. 3 days) for uncomplicated deliveries. Horton et al. (1989) examined the use of obstetrical care among military (all services) and civilian families. Military families (N = 407) were defined as having at least one parent on active duty; thus, these data represent female soldiers and civilian wives of soldiers. Comparing military with civilian women, the initial prenatal visit occurred in the first trimester for 57 versus 64 percent, in the second trimester for 32 versus 29 percent, and in the third trimester for 11 versus 6 percent, respectively. These data contrast with results from a self-report survey of all four services showing that 82 percent of active-duty women received prenatal care in the first trimester of their most recent pregnancy (Bray et al., 1995). Mean birth weight (3,200 g), gestational age (39 weeks), and Apgar scores (8/9) were not significantly different between groups. It should be emphasized that the studies by Horton are based on data from a 1980 survey. Thus, many factors, including the ethnic diversity of the military population, have changed considerably. Further, there was no indication of the proportion of soldiers in the population studied.

To describe pregnancy experiences in the military, a survey was conducted in which 345 active-duty obstetric patients from the Army, Air Force, Navy, and Marine Corps were interviewed (Evans and Rosen, 1996). Of the respondents, 76 percent were married, 55.4 percent of the pregnancies were planned, and 51 percent of the women did not believe there was a good time to become pregnant in one's military career. The majority of women reported that pregnancy had no effect on their career opportunities. Fifty-eight percent had been pregnant at least

Suggested Citation:"6 Pregnancy and Lactation and Postpartum Return-To-Duty Fitness." Institute of Medicine. 1998. Assessing Readiness in Military Women: The Relationship of Body, Composition, Nutrition, and Health. Washington, DC: The National Academies Press. doi: 10.17226/6104.
×

once. Reproductive history revealed the following past pregnancy problems: 15 percent had premature deliveries, 26 percent had abortions, 43 percent had miscarriages, and 22 percent had cesarean-section deliveries. Self-reported problems during the current pregnancy were as follows: 55 percent had no pregnancy complications, 26 percent had one problem, 10 percent were confined to bedrest, 7 percent were hospitalized; and 12 percent were exposed to hazardous materials. Since being pregnant, many reduced their use of alcohol (59%), cigarettes (22%), or caffeine (81%), although many had never used alcohol (39%), cigarettes (75%), or caffeine (12%).

Only 20 percent of participants had work reassignments due to their pregnancy because of physical requirements (34%), exposure to hazardous chemicals (12%), both (49%), or for undisclosed reasons (6%). Those who were reassigned reported greater psychological distress, harassment-discrimination, work absences, medical problems, and intentions to leave the organization. Of those reassigned, however, 80 percent agreed that reassignment was necessary. The study showed that the work experiences of the pregnant military women played a primary role in their decisions to leave. The extent to which pregnancy was perceived and treated positively or negatively contributed to attrition and, therefore, to military readiness. This finding contradicted Navy data, described earlier, on the perspective of supervisors regarding pregnancy and its interference with duties.

In contrast to the considerable number of studies on the influences of pregnancy and childbirth themselves on the military work environment, few studies have examined the impact of multiple pregnancies (family size) on operational effectiveness. Overall, 65 percent of active-duty women are childless, approximately 19 percent have one child, 11 percent have two children, and 4 percent report 3 or more children (this last figure varies by service and rank from 2.3 to 5.5%); thus, 15 percent of active-duty women have 2 or more children (Table 6-6). A study of active-duty Navy personnel to determine whether there were gender differences in absenteeism rates from duty (as measured by supervisor-completed work diaries) found that in shore commands, 11 minutes more work time was lost per day by parents than by nonparents, but there was no difference in lost work time between male and female parents. Single and married parents lost equal amounts of work time (Thomas et al., 1993). When data from a self-report survey conducted recently across all services were used to examine the effect of family size on self-perceived work performance or lost work time, no effect was found (Evans and Rosen, 1996).

Army

Severe antenatal morbidity was common among healthy women (N = 1,825) enlisted in the Army (Adams et al., 1994). Pregnant women (27%) were hospitalized antenatally for the following reasons: preterm labor (44%), preeclampsia (10.3%), hyperemesis (5.5%), and urinary tract or kidney infection (4.7%). African American enlisted women in the Army had a cumulative probability of preterm delivery (13.5%) that was higher than that for Caucasian enlisted women (10.5%) (Adams et al., 1993). Hazard ratio was not uniform across all gestational ages. The African American/Caucasian difference was not significant at 33 to 36 weeks, when most

Suggested Citation:"6 Pregnancy and Lactation and Postpartum Return-To-Duty Fitness." Institute of Medicine. 1998. Assessing Readiness in Military Women: The Relationship of Body, Composition, Nutrition, and Health. Washington, DC: The National Academies Press. doi: 10.17226/6104.
×

TABLE 6-6 Parity among Active-Duty Servicewomen (Expressed as Percentage of Total Number of Women in that Service and Rank) as of June 1997

Service

Rank

0 Children

1 Child

2 Children

3+ Children

Army

Enlisted

57.7

22.9

13.9

5.5

 

Officer

67.9

16.1

11.7

4.3

Air Force

Enlisted

67.7

18.8

10.2

3.3

 

Officer

69.5

13.6

11.9

5.0

Marine Corps

Enlisted

76.1

15.3

6.3

2.3

 

Officer

77.7

10.2

8.3

3.7

Navy

Enlisted

67.9

19.8

9.2

3.0

 

Officer

71.4

13.3

10.9

4.4

Total

Enlisted +

65.4

19.4

11.2

4.1

 

Officer

 

 

 

 

 

SOURCE: Defense Manpower Data Center (Rosslyn, Va., 1997).

preterm deliveries occur, nor for spontaneous rupture of membranes or idiopathic preterm labor, the most common causes of preterm delivery. African American-Caucasian hazard ratios were greatest and significantly different for all deliveries before 33 weeks and for medically indicated preterm deliveries that were required because of severe preeclampsia, fetal growth restriction, or fetal compromise. Caucasian servicewomen had slightly higher rates of preterm delivery compared with their civilian counterparts, whereas African American servicewomen had rates that were less than would have been expected (Adams et al., 1995).

In a case control study (N = 604 preterm cases and N = 6,070 controls) of active-duty primigravidas in the Army, those employed in the highest physical activity levels (heavy and very heavy) had increased odds of preterm delivery ranging from 1.69 to 1.75 (Ramirez et al., 1990). In a logistic model, three independent predictors for preterm delivery were identified: physical activity, race, and military pay grade. Other significant risk factors (not necessarily independent) for preterm delivery included age less than 20 years, non-Caucasian race, pay grades E1 to E3, less than 2 years military service, a never-married status, and an occupational aptitude score less than 100.

Navy

In a study comparing birth outcome of 100 active-duty Navy women with that of 100 civilian spouses of Navy servicemen, mean birth weight (3,531 ± 0.38 g [7.768 ± 0.845 lb] vs. 3,471 ± 463 g [7.636 ± 1.019 lb]) and gestational age (39.9 vs. 39.8 weeks) were not statistically different between Naval active-duty women and controls (Messersmith-Heroman et al., 1994).

Suggested Citation:"6 Pregnancy and Lactation and Postpartum Return-To-Duty Fitness." Institute of Medicine. 1998. Assessing Readiness in Military Women: The Relationship of Body, Composition, Nutrition, and Health. Washington, DC: The National Academies Press. doi: 10.17226/6104.
×

Among active-duty Navy servicewomen (N = 331), rates of cesarean deliveries, transfer for preterm complications, transfer of patients at less than 35 weeks gestation to tertiary care centers, pregnancy-induced hypertension, and intrauterine growth retardation were greater than rates seen among dependent wives of active-duty personnel (N = 1,218) (Magann and Nolan, 1991). Despite access to prenatal care, active-duty women were at higher risk of complications than were military dependent wives. In a subsequent Navy study of 300 consecutive pregnancies of active-duty women, increased maternal age was associated with a significant increase in pregnancy-associated complications of cesarean delivery, operative vaginal delivery, pregnancy-induced hypertension, preterm labor, maternal transport for fetal indications, intrauterine growth retardation, intrauterine fetal death, postpartum hemorrhage, placenta previa, and 5-min Apgar less than 7 (Magann et al., 1995a). In gravidas more than 65 in (1.65 m) in height with gestational weight gain greater than 42 lb (19 kg), there were more complications of pregnancy. Marital status and military occupational specialty (MOS) did not influence pregnancy outcome significantly (Magann et al., 1995b). There were no significant differences in the incidence of medical complications of pregnancy in MOS groups (I = 67%, II = 58%, III = 48%, IV = 53%).

The 1993 Naval Reproductive Outcome Survey (Personal communication, S. Hilton, Division of Health Sciences, Naval Health Research Center, San Diego, Calif., 1996) provided preliminary fetal outcome data on 1,170 pregnancies (Table 6-7). The rates of small-for-gestational-age births were 3 percent for Caucasian, 4 percent for African American, and 2 percent for other women. There were no significant differences in gestation duration (37.2 vs. 37.3 weeks), detection of pregnancy (6.5 vs. 6.0 weeks), and gestation weight gain (36.6 vs. 36.2 lb [16.6 vs. 16.4 kg]) in women who were aboard ship until a mean of 18.2 weeks compared with women who were on shore. The proportions diagnosed with pregnancy-induced hypertension were similar in African American and Caucasian women in the Navy and Marine Corps (Irwin et al., 1994).

TABLE 6-7 1995 Naval Reproductive Outcome Survey: Fetal Outcome as a Function of Ethnicity

 

Livebirth

Fetal Death

Total

 

N

%

N

%

N

%

Caucasian

653

92

54

8

707

60

African American

300

93

22

7

322

28

Other

134

95

7

5

141

12

Total

1,087

93

83

7

1,170

100

 

SOURCE: S. Hilton (Personal communication, Division of Health Sciences, Naval Health Research Center, San Diego, Calif., 1996).

Suggested Citation:"6 Pregnancy and Lactation and Postpartum Return-To-Duty Fitness." Institute of Medicine. 1998. Assessing Readiness in Military Women: The Relationship of Body, Composition, Nutrition, and Health. Washington, DC: The National Academies Press. doi: 10.17226/6104.
×
Air Force

Despite essentially equal utilization of prenatal care, African American women gave birth to smaller preterm infants than did Caucasian women in the Air Force, even after adjusting for differences in gestational age (Greenberg et al., 1993). Maternal race had little direct effect on the survival of liveborn, preterm infants in this population. Preeclampsia was more frequent in African American women (21 vs. 14%). Nulliparas were at increased risk of pregnancy-induced hypertension (RR = 2.2) compared with parous women, but there was little association with age, race, marital status, or educational level.

Summary

An estimated 9 percent of active-duty women in all service branches are pregnant at any given time (Verdugo, 1996), a figure that, apparently, has varied little over the last 20 years (Hoiberg and White, 1991). Available data suggested that pregnancy rates among active-duty women were lower than those of their age-matched civilian peers (Bray, 1996; Bray et al., 1995; Verdugo, 1996) and that rates drop substantially during deployment. For example, in the first 7 months of Operation Joint Endeavor, 3.4 percent of Army women were evacuated due to pregnancy (Verdugo, 1996).

DoD-wide data on pregnancy complications are not available; studies on pregnancy outcome have been small and do not always distinguish between active-duty women and female military dependents. The percentage of active-duty women receiving prenatal care in the first trimester appears higher than that of civilian women. Active-duty women report a high incidence of pregnancy problems. Only 20 percent of women who participated in a DoD-wide survey reported having had work reassignments due to pregnancy; of these, 80 percent agreed with its necessity although many of these women reported great difficulties with the reassignment. Risk factors for preterm delivery among Army women include heavy on-the-job physical activity, non-Caucasian ethnic origin, military pay grade below Enlisted level 4, age less than 20, unmarried status, and low occupational aptitude test score. Active-duty Navy women also had rates of pregnancy complications that were higher than civilian wives of active-duty personnel. Pregnancy complication rates were not associated with MOS or marital status, but were associated with high gestational weight gain. Studies of pregnancy outcome among active-duty Air Force women have shown that African American women were at increased risk of preeclampsia and of giving birth to smaller preterm infants, but that rates of pregnancy-induced hypertension and infant mortality were unaffected by ethnic origin.

Exercise And Pregnancy

The American College of Obstetricians and Gynecologists (ACOG) has published guidelines for exercise during pregnancy and the postpartum period (1994). In the absence of obstetric and medical complications, women can engage in moderate levels of physical activity to maintain cardiovascular and muscular fitness throughout pregnancy and the postpartum period. Although

Suggested Citation:"6 Pregnancy and Lactation and Postpartum Return-To-Duty Fitness." Institute of Medicine. 1998. Assessing Readiness in Military Women: The Relationship of Body, Composition, Nutrition, and Health. Washington, DC: The National Academies Press. doi: 10.17226/6104.
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maternal sense of well-being may be enhanced, no level of exercise has been shown to improve perinatal outcome. There are no data that indicate deleterious effects of moderate exercise on the fetus, except for findings of lower birthweights among offspring of women who continue to exercise vigorously throughout pregnancy (Clapp and Little, 1995).

The ACOG recommendations are as follows:

  1.  Pregnant women can continue to exercise and derive benefit from mild-to-moderate exercise routines. Regular exercise (at least three times a week) is better than intermittent activity.
  2.  Women should avoid exercise in supine position after the first trimester and avoid periods of prolonged, motionless standing.
  3.  Women should stop exercising when fatigued and not exercise to exhaustion.
  4.  Avoid exercise that may involve loss of balance and potential for abdominal trauma.
  5.  Eat an adequate diet to cover the additional needs of pregnancy and exercise.
  6.  Women who exercise in the first trimester should augment heat dissipation by ensuring adequate hydration, appropriate clothing, and optimal environmental surroundings during exercise.
  7.  Many of the physiologic and morphologic changes of pregnancy persist 4 to 6 weeks postpartum; therefore, resume prepregnancy routines gradually.
  8. In addition to these guidelines, the ACOG advises that body building or strength training during pregnancy can strengthen muscles and prevent muscle pains that are common during pregnancy. They recommend, however, that strength training be done under expert supervision to help prevent injuries to muscle and joints, using slow, controlled movements and performing sets of no more than 10 repetitions. Research has not been conducted on the benefits or risks of strength training for pregnant women.

    A number of obstetric and medical conditions preclude pregnant women from participation in exercise. The following conditions should be considered contraindications to exercise during pregnancy:

    •  pregnancy-induced hypertension,
    •  preterm rupture of membranes,
    •  preterm labor during current or previous pregnancy,
    •  incompetent cervix/cerclage,
    •  persistent second or third trimester bleeding, and
    •  intrauterine growth retardation.

    Exercising women should stop exercising if one of the following symptoms occurs: vaginal bleeding, abdominal pain, severe tachycardia, chest pain, severe breathlessness, headache, loss of muscle control, dizziness, or nausea. Consultation with a physician is encouraged.

    Lower gestational weight gain and birth weight among women who exercise through pregnancy have been demonstrated in some (Bell et al., 1995; Clapp, 1990; Clapp and Dickstein, 1984; Clapp and Little, 1995) but not all studies (Sternfeld et al., 1995). The effect of endurance exercise on pregnancy outcome was investigated in pregnant women who never exercised,

Suggested Citation:"6 Pregnancy and Lactation and Postpartum Return-To-Duty Fitness." Institute of Medicine. 1998. Assessing Readiness in Military Women: The Relationship of Body, Composition, Nutrition, and Health. Washington, DC: The National Academies Press. doi: 10.17226/6104.
×

stopped exercise by the twenty-eighth week of gestation, or continued exercise into the third trimester (Clapp and Dickstein, 1984). Complications of bleeding and premature rupture of membranes contributed to cessation of exercise in some women. Gestational weight gain was significantly lower (26.9 vs. 32.2 lb [12.2 vs. 14.6 kg]), gestational duration was shorter (273.7 vs. 281 days) and birth weight, adjusted for gestational age, was 500 g (17.5 oz) lower in women who exercised into the third trimester. Of 131 well-conditioned, recreational athletes who had an uneventful first half of pregnancy, 87 continued to exercise at 50 percent of preconceptional level throughout pregnancy (Clapp, 1990). Preterm labor was similar in both groups (9%). Exercisers went into labor earlier (277 vs. 282 days), and had fewer cesarean (6 vs. 30%) and vaginal (6 vs. 20%) operative deliveries, and shorter duration of active labor (264 vs. 382 minutes). Birth weight was reduced among the exercisers compared with women who had stopped exercising in the first trimester (117.9 vs. 132.2 oz [3,369 vs. 3,776 g]). Recreational exercise through pregnancy (running, aerobics, cycling, swimming, stairmaster) was associated with decreased gestational weight gain (29 vs. 36 lb [13 vs. 16.3 kg]), diminished subcutaneous fat deposition (0.85 vs. 1.22 in [21.8 vs. 31.3 mm]), and decreased birth weight (115.15 vs. 127.05 g [3,290 vs. 3,630 g]) (Clapp and Little, 1995). In women who exercised vigorously through their third trimester, a dose-dependent reduction in mean birth weight was seen with increasing amounts of weekly exercise (Bell et al., 1995). Birth weight was significantly lower (-11 oz [-315 g]) in women who exercised five to seven times per week than in controls, due primarily to reduced gestational age at delivery rather than fetal growth retardation at term. Incidence of low birth weight infants (< 87.5 oz [< 2,500 g]) was 10 percent in the 58 exercisers compared with 2 percent in the 48 controls. In contrast to the above studies, when four levels of exercise, from vigorous walking at least three times per week for at least 20 minutes to aerobic exercise less than once a week in 388 women, were monitored from 16.5 weeks through delivery (Sternfeld et al., 1995), birth weight, gestational age, and gestational weight gain were unrelated to the level of exercise. Most women substantially decreased exercise during pregnancy.

Active women's enhanced cardiorespiratory responses to acute exercise were maintained during pregnancy if they continued an aerobic fitness program. Pivarnik et al. (1993), Sady et al. (1988), and Lotgering et al. (1991) found that VO2max did not change from pregnancy to the postpartum period in subjects of varying fitness levels; however, in studies in which aerobic capacity was assessed prior to pregnancy, VO2max was found to be higher during prepregnancy compared with 4 to 8 weeks postpartum in one study (South-Paul et al., 1992), but unchanged at 6 to 8 weeks postpartum, and increased at 12 to 20 weeks postpartum in another study (Clapp and Capeless, 1991).

Fit women who exercise prior to pregnancy may respond differently and may exercise at a higher intensity than sedentary women who wish to adopt an exercise program during pregnancy. Physically conditioned women can perform at a higher exercise power output than sedentary women without inducing fetal hypoxic stress (Webb et al., 1994). Despite higher cycling power output in the exercising versus sedentary group, mean fetal heart rate was similar in both groups. Nevertheless, nearly all women voluntarily decrease the intensity and duration of exercise as pregnancy progresses.

In general, the fetus appears to tolerate maternal exercise well (Clapp et al., 1993). During and after exercise, the fetal heart rate usually increases about 10 to 30 bpm. Fetal bradycardia

Suggested Citation:"6 Pregnancy and Lactation and Postpartum Return-To-Duty Fitness." Institute of Medicine. 1998. Assessing Readiness in Military Women: The Relationship of Body, Composition, Nutrition, and Health. Washington, DC: The National Academies Press. doi: 10.17226/6104.
×

has been reported infrequently, usually in the recovery phase of exercise. No adverse effects of the bradycardia were noticed. In another study, decreased fetal movement and breathing were observed after acute exercise (Winn et al., 1994). Because of the difficulties of measuring fetal state, particularly during exercise, and because of the lack of long-term outcome studies, questions remain as to the lasting effects of vigorous exercise on the fetus.

During exercise, elevated core temperatures theoretically could exert a teratogenic effect on the fetus, but maternal adaptations appear to protect it. Peak rectal temperature reached during exercise decreased by 0.3°C at 8 weeks and fell at a rate of 0.1°C/mo through 37 weeks of gestation (Clapp, 1991). Pregnant women without complications can maintain thermal balance during 20 minutes of exercise at 70 percent maximal heart rate on land or water (McMurray et al., 1991).

Although moderate levels of physical activity during pregnancy may be recommended for healthy women without obstetric complications, conservatism is warranted, given the limited number of human studies, small sample sizes, incomplete accounting of subjects who were eliminated because they developed complications, subject self-selection to exercise, difficulties monitoring the fetus during exercise, and inadequate pregnancy outcome data.

Summary

According to ACOG guidelines, in the absence of obstetric and medical complications, women can engage in moderate levels of physical activity to maintain cardiovascular and muscular fitness throughout pregnancy and the postpartum period. No level of exercise has been shown to improve perinatal outcome; lower birth weight has been observed among offspring of women who continue to obtain vigorous exercise throughout pregnancy. Lower gestational weight gain and birth weight among women who exercise during pregnancy has been observed in some but not all studies. There is evidence that aerobic capacity decreases during pregnancy in women of all activity levels, and increases again at 12 to 20 weeks postpartum. Women who were physically active prior to pregnancy can exercise with a greater intensity during pregnancy than previously sedentary women; nevertheless, most physically active women voluntarily decrease the intensity and duration of exercise as pregnancy progresses. Fetal tolerance for maternal exercise appears adequate; maternal adaptations appear to protect the fetus from elevations in maternal core temperature.

Postpartum Changes In Weight And Physical Fitness

No data were found on the percentage of military women who attain weight, body fat, and fitness standards by 6 months postpartum. Gestational weight gain is the major determinant of postpartum weight retention, but unfortunately, representative statistics on gestational weight gain are not available on military servicewomen.

In a prospective study of 105 consecutive deliveries of active-duty women at the Naval Hospital at Pensacola, Florida, mean weight gain of women with complications was 36 lb (16 kg) and without complications 33 lb (15 kg) (Magann et al., 1995a, 1996). Birthweights averaged

Suggested Citation:"6 Pregnancy and Lactation and Postpartum Return-To-Duty Fitness." Institute of Medicine. 1998. Assessing Readiness in Military Women: The Relationship of Body, Composition, Nutrition, and Health. Washington, DC: The National Academies Press. doi: 10.17226/6104.
×

114 ± 21.1 oz (3,257 ± 603 g) and 118.3 ± 13.5 oz (3,379 ± 386 g), respectively. The number of women who fell into categories of gestational weight gain less than 25 lb (11.5 kg), 25 to 35 lb (11.5 to 16 kg), and greater than 35 lb (16 kg) was 18, 44, and 43, respectively. Women who gained less than 25 lb (11.5 kg) during pregnancy developed preterm labor more often. In another study, active-duty Navy women gained significantly less (29 vs. 31 lb [13 vs. 14 kg]) than civilian controls (p < 0.05) (Messersmith-Heroman et al., 1994). Clearly, more complete information on gestational weight gain is needed on active-duty women in all services.

Gestational Weight Gain

The Institute of Medicine (IOM) recommendations for gestational weight gain have been endorsed by ACOG. Rather than recommending a single figure, the IOM recommends an ideal range, recognizing the natural variability observed in gestational weight gain among healthy, pregnant women (Table 6-8). Because maternal prepregnancy body size modifies the relation between gestational weight gain and birth weight, separate recommendations are made for underweight, normal weight, and overweight women. Very young adolescents and African American women should aim for upper limit of range and short women should aim for the lower limit of range.

Since the release of the IOM recommendations on gestational weight gain, a number of reports have validated the recommendations in terms of infant outcome and postpartum weight retention (Cogswell et al., 1995; Edwards et al., 1996; Hickey et al., 1993; Muscati et al., 1996; Parker and Abrams, 1992; Siega-Riz et al., 1994). A study of 7,000 term births at the University of California, San Francisco, confirmed that compliance with the IOM recommendations was associated with lower risk of delivering small-for-gestational-age or large-for-gestational-age

TABLE 6-8 Recommended Total Weight Gain Ranges for Pregnant Women,* by Prepregnancy Body Mass Index (BMI)

 

Recommended Total Gain

 

Weight-for-Height Category

kg

lb

Low (BMI < 19.8)

12.5–18

28–40

Normal (BMI 19.8 to 26.0)

11.5–16

25–35

High (BMI > 26.0 to 29.0)

7–11.5

15–25

* Young adolescents and black women should strive for gains at the upper end of the recommended range. Short women (<157 cm or 62 in) should strive for gains at the lower end of the range.

BMI is calculated using metric units.

The recommended target weight gain for obese women (BMI > 29.0) is at least 6.0 kg (sic) (15 lb).

SOURCE: IOM (1990).

Suggested Citation:"6 Pregnancy and Lactation and Postpartum Return-To-Duty Fitness." Institute of Medicine. 1998. Assessing Readiness in Military Women: The Relationship of Body, Composition, Nutrition, and Health. Washington, DC: The National Academies Press. doi: 10.17226/6104.
×

infants, cesarean deliveries, and excessive postpartum weight retention (Parker and Abrams, 1992). For 655 nonobese, multiparous African American women, the risk of fetal growth retardation was 18, 10, and 4 percent for women who gained less than, within, or more than, respectively, the IOM recommendations for their BMI (Hickey et al., 1993). For nonobese Caucasian women, comparable percentages were 20.9, 19.1, and 10.5 percent fetal growth retardation.1 For 148 obese women, fetal growth restriction occurred in 25 percent of those with a low gestational weight gain compared with 4 percent of those who gained the recommended amount (> 13 lb [> 6 kg]). More women with low BMI gained less than recommended as compared with other groups. Since African American women in each pregravid BMI category delivered increasingly larger infants as they met or exceeded recommended gestational weight gain, it was concluded that African American women should strive for the upper end of the recommended range for pregravid BMI.

To determine the relationship between increased gestational weight gain and birth weight for low-income populations, Caucasian, African American, and Hispanic women (N = 53,541) from eight states were studied between 1990 and 1992 (Cogswell et al., 1995). The risk for low birth weight decreased with increasing gestational weight gain for average-weight women. For very-overweight women (BMI > 29), an upper limit of 25 lb (11.5 kg) was recommended to reduce the risk for high birth weight. In a study comparing 660 normal weight and 683 obese pregnant women, obese women who gained no weight or lost weight were at higher risk for delivery of an infant of birth weight less than 105 oz (3,000 g) or gestational age than were obese women who gained 15 to 25 lb (7–11.5 kg); those who gained more than 35 lb (16 kg) were at twice the risk for delivery of an infant of birth weight greater than 140 oz (4,000 g) (Edwards et al., 1996). To optimize fetal growth, a gestational weight gain of 15 to 25 lb (7–11.5 kg) for obese women and 25 to 35 lb (11.5–16 kg) for normal-weight women appears to be appropriate.

Factors influencing the risk of gaining outside the IOM recommendations for gestational weight gain were investigated in African American (N = 2,617) and Caucasian (N = 1,253) women who delivered at Johns Hopkins Hospital between 1987 and 1989 (Caulfield et al., 1996). The mean gestational weight gain of African American women was 29.3 ± 15.0 lb (13.3 ± 6.8 kg); 38.3 percent gained less and 33.6 percent gained more than recommended. Mean gestational weight gain was greater in Caucasian women (mean = 33.3 ± 12.6 lb [15.1 ± 5.7 kg]) with 24.8 percent gaining less and 43.0 percent gaining more. Factors identified with gaining less were: being younger, shorter, thinner, or less educated; being African American; and a smoker. Factors associated with gaining more were: being taller, heavier, primiparous, Caucasian, and hypertensive. African American women were 1.51 times more likely to undergain and 0.89 times less likely to overgain than Caucasian women.

In the 1988 National Maternal and Infant Health Survey, racial differences were larger: 29.1 percent of African American and 36.7 percent of Caucasian women reportedly gained within IOM recommendation (Keppel and Taffel, 1993). Of those gaining outside the recommendations, African American women were 50 percent more likely to undergain, but only 10 percent were less likely to overgain. African American women were more likely to retain at

1  

In this study, the Alabama standards were used; these set fetal growth retardation at higher birth weight for Caucasian than for African American newborns, thus, these percentages are not straight prevalence.

Suggested Citation:"6 Pregnancy and Lactation and Postpartum Return-To-Duty Fitness." Institute of Medicine. 1998. Assessing Readiness in Military Women: The Relationship of Body, Composition, Nutrition, and Health. Washington, DC: The National Academies Press. doi: 10.17226/6104.
×

least 20 lb (9 kg) than were Caucasian women (adjusted odds ratio = 2.2) (Parker and Abrams, 1992). African American women were more likely to have inadequate gestational weight gain but not more likely to have excessive gain. Moreover, African American women appear less likely to lose weight postpartum.

Postpartum Weight Loss

Postpartum weight retention increases with gestational weight gain (Abrams, 1994; Parker and Abrams, 1992). Focusing on average postpartum weight retention can obscure subsets of women who retain far more weight. The National Maternal and Infant Health Survey (Keppel and Taffel, 1993) showed that median weight retention in Caucasian women 10 to 18 months postpartum was 1.6 lb (0.7 kg), but 30 percent of obese women who gained more than 25 lb (11.5 kg) retained more than 14 lb (6 kg). Postpartum weight retention was higher at every level of prenatal gestational weight gain for African American women. Although high gestational weight gain is associated with more postpartum weight retention, women whose gains are within the recommended IOM ranges (see Table 6-8) are half as likely to retain 20 lb (9 kg) or more than those whose gains are above the upper limit of the range. However, it must be emphasized that only 30 to 40 percent of women gain within the IOM recommendations.

If pregnant women gain weight according to the IOM recommendations and lose approximately 17.31 lb (7.85 kg) at delivery and 1.54 lb/mo (0.7 kg/mo) thereafter, those with low pregravid BMI (< 19.8) would retain 0.9 to 13 lb (0.4–5.9 kg), and women with normal BMI (19.8–26.0) would retain 1.3 to 8.8 lb (0.6–4.0 kg) at 6 months postpartum. In actuality, the majority of pregnant women gain outside of the IOM recommendations, rates of postpartum weight loss are extremely variable, and many women do not attain their prepregnancy weight by 6 months postpartum. Weight changes through pregnancy and the postpartum period are influenced in part by hormonal changes. However, gestational weight gain and postpartum weight loss are amenable to advice, at least on a population basis. Women are encouraged to gain weight within the IOM recommendations during pregnancy and to lose weight postpartum through appropriate nutritional counseling and exercise programs.

In a predominantly Hispanic population (N = 8,736) in Los Angeles, monitoring gestational weight gain revealed that 47.8, 36,6, and 28.4 percent of underweight, normal weight, and overweight women gained within the IOM recommendations (Siega-Riz et al., 1994). Postpartum weight retention was examined in 158 low income women (Parham et al., 1990). The mean gestational weight gain was 28.4 ± 12.8 lb (12.9 ± 5.8 kg), with 44 percent gaining more than 30 lb (13.6 kg) and 25 percent gaining less than 20 lb (9.1 kg). According to the gestational weight gain tertiles, postpartum weight retention 6 to 9 months later was 6.6, 7.1, and 13.4 lb (3.0, 3.2, and 6.1 kg) for the lower (gestational weight gain = 15.2 lb [6.9 kg]), middle (28 lb [12.7 kg]), and upper (42.5 [19.3 kg]) tertiles, respectively.

In 371 Canadian women with uncomplicated pregnancies, gestational weight gain averaged 35.5 ± 14.1 lb (16.1 ± 6.4 kg) (fifteenth to eighty-fifth percentiles, 23 to 49.8 lb [10.4 to 22.6 kg]) (Muscati et al., 1996). Postpartum weight retention at 6 weeks postpartum equaled 11.7 ± 12.6 lb (5.3 ± 5.7 kg) (fifteenth to eighty-fifth percentiles, -18.1 to 61.1 lb [-8.2 to 27.7 kg]); approximately 75 percent retained greater than 2.5 kg. In a large cohort of Swedish women (N =

Suggested Citation:"6 Pregnancy and Lactation and Postpartum Return-To-Duty Fitness." Institute of Medicine. 1998. Assessing Readiness in Military Women: The Relationship of Body, Composition, Nutrition, and Health. Washington, DC: The National Academies Press. doi: 10.17226/6104.
×

1,423), at 1 year postpartum, net gain was 3.3 ± 7.9 lb (1.5 ± 3.6 kg); 30 percent had lost weight, 56 percent had gained 0 to 11 lb (0–5 kg), and 14 percent had gained more than 11 lb (5 kg) (Öhlin and Rössner, 1990).

Predictors of postpartum weight loss included ethnicity, gestational weight gain, prepregnancy weight, parity, and prenatal exercise (Boardley et al., 1995; Schauberger et al., 1992). Weight retained by African American women was 6.4 lb (2.9 kg) more than that by Caucasian women (Boardley et al., 1995). African American women had higher energy intake, higher percentage dietary fat, and lower prenatal and postnatal activity. In a study of predominantly Caucasian women (N = 795), the average weight retention at 6 months postpartum was 3.1 lb (1.4 kg); 37 percent of women had returned to their prepregnancy weight (Schauberger et al., 1992).

Although lactation unquestionably creates an energy deficit for women, several other overriding factors appear to determine postpartum weight change. Changes in body weight and composition in response to lactation are highly variable among individuals. Mean rates of weight loss across studies of lactating women range from -0.95 to -1.98 lb/mo (-0.43 to -0.90 kg/mo) in the first 6 months postpartum (Butte et al., 1984; Dewey et al., 1993; Manning-Dalton and Allen, 1983; Naismith and Ritchie, 1975; Sohlström and Forsum, 1995). However, studies comparing postpartum weight changes in lactating and nonlactating women are not unequivocal; most indicated comparable rates of weight loss between feeding groups. Of the factors associated with postpartum weight change, gestational weight gain is by far the most consistent and strongest predictor across all studies.

Average postpartum weight changes conceal the extreme variability among women (Lederman, 1993). In addition to gestational weight gain, parity, age, and ethnicity have all been shown to influence postpartum weight change. While most women approach their prepregnancy weight by 6 months, subsets of women retain substantial weight.

Use of Military Body Composition Equations in Postpartum Women

The use of standard military equations for estimation of body fat at return-to-duty testing has not been validated in postpartum women. Fat is deposited preferentially at certain body sites during pregnancy, which may bias body fat estimates. For instance, the Army and Navy equations may overestimate body fat, since these equations use hip circumference, a predominant site of fat deposition. The study of Westphal and coworkers (1995) on women in BCT found no differences in average body fat or fat deposition between nulliparous women and those who had given birth. However, length of time since delivery was not considered.

Changes in Postpartum Physical Fitness

In a study by Carpenter et al. (1990), absolute rates of VO2max (liters/min) on the cycle and treadmill fell postpartum, but when these rates are expressed as a function of body weight (liters/kg/min), there was no significant reduction. In recreational athletes, the exercise duration-intensity index decreased 30 to 45 percent during pregnancy, mainly due to decreased intensity; a further 20 percent decrease was observed initially postpartum (Clapp and Capeless, 1991). By 12

Suggested Citation:"6 Pregnancy and Lactation and Postpartum Return-To-Duty Fitness." Institute of Medicine. 1998. Assessing Readiness in Military Women: The Relationship of Body, Composition, Nutrition, and Health. Washington, DC: The National Academies Press. doi: 10.17226/6104.
×

weeks postpartum, the duration-intensity index was 20 percent less than the preconceptional level and remained there; the decrease was due to duration. A significant 7.3 percent increase in absolute VO2max was evident 12 to 20 weeks postpartum and was maintained at the time of final testing 36 to 44 weeks postpartum. These data indicate that there is a small but significant postpartum increase in VO2max in recreational athletes who maintain a moderate-to-high level of exercise performance during and after pregnancy, possibly due to the training effect of increased physical work daily. In nine women, cycle ergometry was done at 26 weeks of pregnancy and 2 and 7 months postpartum (Sady et al., 1990). Antepartum resting cardiac output, heart rate, and stroke volume were higher, and arteriovenous difference was lower, than postpartum. No significant differences were seen in VO2max or heart rate among the three time periods.

Summary

Gestational weight gain is the primary determinant of postpartum weight retention. Data on gestational weight gain and postpartum weight loss are not available for a representative sample of active-duty women.

Birth weight increases with increasing gestational weight gain. The IOM has published recommended ranges of gestational weight gain to optimize fetal growth, based on pregravid BMI, age, and ethnicity. These recommendations have been endorsed by several other groups and validated with respect to infant outcome. Many women gain outside of the recommended ranges. Factors associated with low gestational weight gain include young age, short stature, low body weight, lower educational achievement, smoking, and African American ethnic origin.

Postpartum weight retention is highly variable, depending in part on gestational weight gain, hormonal levels, parity, age, ethnicity, decision to breastfeed, and other lifestyle factors. gestational weight gain within ranges recommended by IOM is associated with less risk of high postpartum weight retention. A subset of women, obese women with gestational weight gain of more than 25 lb (11.5 kg), appears to retain significantly more weight than average. Postpartum weight retention is higher at every level of gestational weight gain for African American women. Many women do not return to prepregnancy weight by 6 months postpartum. The use of military equations for anthropometric estimation of body fat at return to duty has not been validated.

Results of a small number of studies indicate that there is a small but significant postpartum increase in maximal aerobic capacity in women who maintain a moderate-to-high level of exercise performance during and after pregnancy.

Lactation

Breastfeeding is recommended as the preferred method of infant nutrition by the American Academy of Pediatrics, American College of Obstetricians and Gynecologists, and American Academy of Family Physicians. The recommendation to breastfeed arises from its acknowledged benefits with respect to infant nutrition, gastrointestinal function, host defense, and psychological well-being, as well as to maternal health. The protective effects of breastfeeding have been shown to reduce infant morbidity and associated health care costs. The Healthy People 2000

Suggested Citation:"6 Pregnancy and Lactation and Postpartum Return-To-Duty Fitness." Institute of Medicine. 1998. Assessing Readiness in Military Women: The Relationship of Body, Composition, Nutrition, and Health. Washington, DC: The National Academies Press. doi: 10.17226/6104.
×

goals aim for breastfeeding prevalence of 75 percent at birth and 50 percent at 5 to 6 months postpartum (DHHS, 1991).

Military Studies

With a few exceptions, no data could be located on the prevalence and duration of breastfeeding among military women (Louder and Yoder, 1997; Personal communication, S. Hilton, Division of Health Sciences, Naval Health Research Center, San Diego, Calif., 1996). The 1993 Naval Reproductive Outcome Survey (N = 1,070) indicated a breastfeeding duration of less than 1 month in 18 percent of subjects, 1 to 2 months in 16 percent, 2 to 3 months in 10 percent, greater than 3 months in 21 percent, and 35 percent did not breastfeed at all (Personal communication, S. Hilton, Division of Health Sciences, Naval Health Research Center, San Diego, Calif., 1996). At Lackland AFB, 1,138 deliveries were monitored over a 10-mo period. Of the respondents, 70 percent intended to breastfeed, 24 percent intended to use formula, and the remainder were planning to do both. Women who intended to feed formula had lower educational attainment, shorter pregnancies, later first obstetric appointment, lower sponsor's military rank (junior enlisted to senior officers), less likelihood of being married, and different sponsor's military status (sponsor refers to the responsible individual—self, spouse, or parent—who is on active duty or who is retired from the military). Maternal ethnicity influenced the intent to breastfeed, with African American mothers having the lowest intention rates. At discharge, the actual feeding mode was described as: 47 percent breastfeeding, 12.5 percent mostly breastfeeding, 7 percent doing both, 3.5 percent mostly feeding formula, and 30.3 percent solely feeding formula. No studies could be identified that addressed the impact or potential impact of breastfeeding on readiness.

Lactation and Postpartum Weight Loss

Research on the rate of weight loss during lactation (IOM, 1991) tends to show an average weight loss between 0 and 6 months postpartum of 1.3 to 1.8 lb/mo (0.6–0.8 kg/mo) and between 6 and 12 months postpartum of approximately 0.2 to 0.4 lb/mo (0.1–0.2 kg/mo). However, the rate of weight loss actually shows wide variation among women. Notably, a proportion of women gain weight during lactation (Butte et al., 1984; Manning-Dalton and Allen, 1983). The women with the largest net gestational weight gain tended to lose the most weight postpartum (Manning-Dalton and Allen, 1983). Rates of change in body weight, body fat, and skinfold thickness were not correlated with parameters of lactation performance in the first 4 months of lactation (Butte et al., 1984). However, maternal weight change was significantly correlated with the protein concentration in milk at 6 and 9 months, and with the lipid concentration at 6 months (Nommsen et al., 1991). The amount of energy mobilized from tissue reserves is relatively minor compared with that from dietary sources. The compensatory interaction between dietary energy and tissue mobilization may protect milk synthesis in well-nourished women. As lactation advances and tissue reserves diminish, milk production may be influenced by maternal nutritional status.

Suggested Citation:"6 Pregnancy and Lactation and Postpartum Return-To-Duty Fitness." Institute of Medicine. 1998. Assessing Readiness in Military Women: The Relationship of Body, Composition, Nutrition, and Health. Washington, DC: The National Academies Press. doi: 10.17226/6104.
×

Öhlin and Rössner (1990) monitored weight change in 1,423 Swedish women for 12 months postpartum and found a highly significant correlation between gestational weight gain and weight retention postpartum. Weight loss between 2.5 and 6 months postpartum was significantly higher in women who breastfed exclusively. However, total weight loss between 2.5 and 12 months was not significantly influenced by the duration or intensity of lactation. Changes in weight and skinfold thicknesses were monitored in 151 Irish women for 12 months postpartum (Dugdale and Eaton-Evans, 1989). A pattern of weight loss was seen in the first 6 months, after which weight plateaued. Changes in weight were independent of the duration of breastfeeding, but were influenced by the initial BMI and the desire to lose weight.

There is no evidence that weight loss up to 4 lb/mo (2 kg/mo) has adverse effects on lactation in well-nourished women. Effects of rapid weight loss are unknown, particularly during the first month postpartum when the milk supply is being established.

Physical Activity and Lactation

No adverse effect of vigorous exercise on lactation performance was observed in a group of exercising women (N = 8) compared with sedentary women (N = 8) (Lovelady et al., 1990). The effects of an exercise program on lactation performance were studied in a randomized intervention trial (Dewey et al., 1994). The experimental group engaged in aerobic exercise 45 min/d, 5 d/wk for 12 weeks; and the control group exercised vigorously no more than once per week. An increase in aerobic capacity was seen in the exercising group, but there was no difference in weight loss or body composition, because they consumed more food. No adverse effects on lactation performance or infant weight gain were observed in the exercising group. Women who breastfeed can undertake exercise without jeopardizing milk volume or composition. One report cited a transitory increase in lactic acid in breast milk following exercise, but this did not affect intake as taste is apparently not a problem with most infants (Wallace et al., 1992).

Summary

Numerous physicians' organizations recommend breastfeeding as the preferred method of infant feeding because of its benefits with respect to infant nutrition, gastrointestinal function, host defense, and psychological well-being, as well as its protective effect on maternal health. Except for small studies, no data are available on the prevalence or duration of breastfeeding among active-duty military women. Among a group of Air Force active-duty women and dependents, intention to breastfeed was associated with higher educational attainment, longer pregnancies, earlier first obstetric appointment, higher rank or sponsor rank, marital status, and Caucasian ethnic origin. At hospital discharge, prevalence of women actually breastfeeding (47%) was significantly lower than intention to breastfeed had been (70%).

In studies of civilian women, vigorous physical activity and exercise does not appear to affect lactation performance.

Suggested Citation:"6 Pregnancy and Lactation and Postpartum Return-To-Duty Fitness." Institute of Medicine. 1998. Assessing Readiness in Military Women: The Relationship of Body, Composition, Nutrition, and Health. Washington, DC: The National Academies Press. doi: 10.17226/6104.
×

Nutrition During Pregnancy And Postpartum

A complete guide for nutritional counseling of pregnant and lactating women is available (IOM, 1992). For all pregnant women, a daily supplement of 30 mg of ferrous iron is recommended during the second and third trimesters. The U.S. Public Health Service recommends that all women of childbearing age should consume 400 µg/d of dietary folate for the purpose of reducing their risk of having an infant affected with spina bifida or other neural tube defects (CDC, 1992). The IOM (1998) recommends that an intake of 600 µg/d dietary folate2 be consumed during pregnancy and that 500 µg/d be consumed during lactation. During pregnancy and lactation, women should abstain from smoking. Alcohol should be avoided during pregnancy and should only be consumed in moderation during lactation (IOM, 1990).

In the postpartum period, persistent anemia and musculoskeletal and cardiovascular changes present potential problems for the mother. Women with low iron stores before pregnancy could require 5 to 6 months to recover from iron deficiency and another 4 months or more to replete iron stores. Back pain and injury remain as significant risks in the postpartum period and can be countered by a program of strengthening and stretching exercises for the abdomen, back, and legs.

Concluding Remarks

Pregnancy is compatible with a military career. It represents a short period in a woman's military career and can be accommodated with planning. The rate of pregnancy among active-duty women is lower than that of civilian women of comparable ages; however, given the high rates of unplanned pregnancies among military women, there appears to be a need for education and counseling for all servicemembers on effective birth control and the importance of timing a pregnancy in one's military career. To reduce attrition and enhance military readiness, all supervisory staff need increased training and education regarding pregnancy policy and treatment of pregnant personnel.

Few data are available on pregnancy outcome or the rate of gestational weight gain and postpartum weight loss for active-duty women. The limited data available suggest that pregnancy complications are higher among active-duty women than among civilian women and that active-duty women may tend to seek prenatal care later than their civilian counterparts (however, there are conflicting data regarding this latter point). A 1992 report of the IOM established guidelines for recommended gestational weight gain, which have been endorsed by the ACOG. Many women do not gain within the recommendations. Gestational weight gain is one factor responsible for rate of postpartum weight loss. The use of standard military equations for estimation of body fat at return-to-duty testing has not been validated in postpartum women. If the equations contain waist and hip measurements, they may penalize women unfairly during the child-bearing years.

The ACOG has published guidelines for exercise during pregnancy and the postpartum period (1994). In the absence of obstetric and medical complications, pregnant women can engage in moderate levels of physical activity to maintain cardiovascular and muscular fitness

2  

As dietary folate equivalents (DFEs). 1 DFE = 1 µg food folate = 0.6 µg of folic acid (from fortified food or supplement) consumed with food = 0.5 µg of synthetic (supplemental) folic acid taken on an empty stomach (IOM, 1998).

Suggested Citation:"6 Pregnancy and Lactation and Postpartum Return-To-Duty Fitness." Institute of Medicine. 1998. Assessing Readiness in Military Women: The Relationship of Body, Composition, Nutrition, and Health. Washington, DC: The National Academies Press. doi: 10.17226/6104.
×

throughout pregnancy and the postpartum period. Although maternal sense of well-being may be enhanced with exercise, no level of exercise has been shown to improve perinatal outcome. Except for findings of lower birth weights among offspring of women who continue to exercise vigorously throughout pregnancy, no data indicate deleterious effects of moderate exercise on the fetus. Intent and participation in exercise should be reviewed with the guidance of the woman's obstetrician.

Breastfeeding is recommended as the preferred method of infant nutrition by the American Academy of Pediatrics, American College of Obstetricians and Gynecologists, and the American Academy of Family Physicians. The prevalence and duration of breastfeeding by military women is virtually unknown.

References

Abrams, B. 1994. Weight gain and energy intake during pregnancy. Clin. Obstet. Gynecol. 37:515–527.

ACOG (American College of Obstetricians and Gynecologists). 1994. Exercise during pregnancy and the postpartum period. ACOG Technical Bulletin 189. February. Washington, D.C.: ACOG.

Adams, M.M., J.A. Read, J.S. Rawlings, F.E. Harlass, A.P. Sarno, and P.H. Rhodes. 1993. Preterm delivery among black and white enlisted women in the United States Army. Obstet. Gynecol. 81:65–71.

Adams, M.M., F.E. Harlass, A.P. Sarno, J.A. Read, and J.S. Rawlings. 1994. Antenatal hospitalization among enlisted servicewomen, 1987–1990. Obstet. Gynecol. 84:35–39.

Adams, M.M., A.P. Sarno, F.E. Harlass, J.S. Rawlings, and J.A. Read. 1995. Risk factors for preterm delivery in a health cohort. Epidemiology 6:525–532.

AFI (Air Force Instruction) 40-502. 1994. See U.S. Department of the Air Force, 1994.

AFI (Air Force Instruction) 44-102. 1996. See U.S. Department of the Air Force, 1996.

AR (Army Regulation) 40-501. 1995. See U.S. Department of the Army, 1995.


Bell, R.J., S.M. Palma, and J.M. Lumley. 1995. The effect of vigorous exercise during pregnancy on birth-weight. Aust. N.Z. J. Obstet. Gynaecol. 35:46–51.

Boardley, D.J., R.G. Sargent, A.L. Coker, J.R. Hussey, and P.A. Sharpe. 1995. The relationship between diet, activity, and other factors, and postpartum weight change by race. Obstet. Gynecol. 86:834–838.

Bray, R.M. 1996. Health, fitness, and nutrition among military women and men. Presentation at the workshop on Assessing Readiness in Military Women: The Relationship to Nutrition. September 9–10, Irvine, Calif.

Bray, R.M., L.A. Kroutil, S.C. Wheeless, M.E. Marsden, S.L. Bailey, J.A. Fairbank, and T.C. Harford. 1995. Health behavior and health promotion. Department of Defense Survey of Health-Related Behaviors among Military Personnel . Report No. RTI/6019/06-FR. Research Triangle Park, N.C.: Research Triangle Institute.

Butte, N.F., C. Garza, J.E. Stuff, E.O. Smith, and B.L. Nichols. 1984. Effect of maternal diet and body composition on lactational performance. Am. J. Clin. Nutr. 39:296–306.


Carpenter, M.W., S.P. Sady, M.A. Sady, B. Haydon, D.R. Coustan, and P.D. Thompson. 1990. Effect of maternal weight gain during pregnancy on exercise performance. J. Appl. Physiol. 68:1173–1176.

Caulfield, L.E., F.R. Witler, and R.J. Stoltzfus. 1996. Determinants of gestational weight gain outside the recommended ranges among black and white women. Obstet. Gynecol. 87:760–766.

CDC (Centers for Disease Control and Prevention). 1992. Recommendations for the use of folic acid to reduce the number of cases of spina bifida and other neural tube defects. Morbid. Mortal. Weekly Rep. 41:1–7.

Suggested Citation:"6 Pregnancy and Lactation and Postpartum Return-To-Duty Fitness." Institute of Medicine. 1998. Assessing Readiness in Military Women: The Relationship of Body, Composition, Nutrition, and Health. Washington, DC: The National Academies Press. doi: 10.17226/6104.
×

Clapp III, J.F. 1990. The course of labor after endurance exercise during pregnancy. Am. J. Obstet. Gynecol. 163(6 pt. 1):1799–1805.

Clapp III, J.F. 1991. The changing thermal response to endurance exercise during pregnancy. Am. J. Obstet. Gynecol. 165:1684–1689.

Clapp III, J.F., and E.L. Capeless. 1991. The VO2max of recreational athletes before and after pregnancy. Med. Sci. Sports Exerc. 23:1128–1133.

Clapp III, J.F., and S. Dickstein. 1984. Endurance exercise and pregnancy outcome. Med. Sci. Sports Exerc. 16:556–562.

Clapp III, J.F., and K.D. Little. 1995. Effect of recreational exercise on pregnancy weight gain and subcutaneous fat deposition. Med. Sci. Sports Exerc. 27:170–177.

Clapp III, J.F., K.D. Little, and E.L. Capeless. 1993. Fetal heart rate response to sustained recreational exercise. Am. J. Obstet. Gynecol. 168:198–206.

Cogswell, M.E., M.K. Serdula, D.W. Hungerford, and R. Yip. 1995. Gestational weight gain among average-weight and overweight women: What is excessive? Am. J. Obstet. Gynecol. 172:705–712.

Dewey, K.G., M.J. Heinig, and L.A. Nommsen. 1993. Maternal weight-loss patterns during prolonged lactation. Am. J. Clin. Nutr. 58:162–166.

Dewey, K.G., C.A. Lovelady, L.A. Nommsen-Rivers, M.A. McCrory, and B. Lonnerdal. 1994. A randomized study of the effects of aerobic exercise by lactating women on breast-milk volume and composition. N. Engl. J. Med. 330:449–453.

DHHS (U.S. Department of Health and Human Services). 1991. Healthy People 2000: National Health Promotion and Disease Prevention Objectives. DHHS (PHS) Publ. No. 91-50212. Public Health Service, U.S. Department of Health and Human Services. Washington, D.C.: U.S. Government Printing Office.

DoD (Department of Defense) Directive 1315.7. 1991. See U.S. Department of Defense, 1991.

Dugdale, A.E., and J. Eaton-Evans. 1989. The effect of lactation and other factors on post-partum changes in body-weight and triceps skinfold thickness. Br. J. Nutr. 61:149–153.


Edwards, L.E., W.L. Hellerstedt, I.R. Alton, M. Story, and J.H. Himes. 1996. Pregnancy complications and birth outcome in obese and normal-weight women: Effects of gestational weight change. Obstet. Gynecol. 87:389–394.

Evans, M.A., and L. Rosen. 1996. Women in the military: Pregnancy, command climate, organizational behavior, and outcomes. Technical Report No. HR 96-001, Part I, Defense Women's Health Research Program. Fort Sam Houston, Tx.: U.S. Army Medical Department Center and School.


Flatter, J.R. 1996. First-term attrition due to pregnancy in the Marine Corps: Issues, trends, and options. M.S. Thesis. Naval Postgraduate School, Monterey, Calif.

FM (Field Manual) 21-20. 1992. See U.S. Department of the Army.


Greenberg, D.N., B.A. Yoder, R.H. Clark, C.A. Butzin, and D.M. Null Jr. 1993. Effect of maternal race on outcome of preterm infants in the military. Pediatrics 91:572–577.


Hickey, C.A., S.P. Cliver, R.L. Goldenberg, J. Kohatsu, and H.J. Hoffman. 1993. Prenatal weight gain, term birth weight, and fetal growth retardation among high-risk multiparous black and white women. Obstet. Gynecol. 81:529–535.

Hoiberg, A., and White, J.F. 1991. Health status of women in the Armed Forces. Armed Forces and Society 18:(4):514–533.

Horton, J.A., D.F. Cruess, and M. Korper. 1988. Deliveries in U.S. military and non-federal hospitals, 1980. Mil. Med. 153:611–614.

Horton, J.A., D.F. Cruess, and M. Korper. 1989. Use of obstetrical care compared among military and civilian families. Public Health Rep. 104:309–310.

Suggested Citation:"6 Pregnancy and Lactation and Postpartum Return-To-Duty Fitness." Institute of Medicine. 1998. Assessing Readiness in Military Women: The Relationship of Body, Composition, Nutrition, and Health. Washington, DC: The National Academies Press. doi: 10.17226/6104.
×

IOM (Institute of Medicine). 1990. Nutrition during Pregnancy: Part I, Weight Gain; Part II, Nutrient Supplements. Subcommittee on Nutritional Status and Weight Gain during Pregnancy, Subcommittee on Dietary Intake and Nutrient Supplements during Pregnancy, Committee on Nutritional Status During Pregnancy and Lactation, Food and Nutrition Board. Washington, D.C.: National Academy Press.

IOM (Institute of Medicine). 1991. Nutrition during Lactation. Subcommittee on Lactation, Committee on Nutritional Status during Pregnancy and Lactation, Food and Nutrition Board. Washington, D.C.: National Academy Press.

IOM (Institute of Medicine). 1992. Nutrition during Pregnancy and Lactation: An Implementation Guide. Subcommittee for a Clinical Application Guide, Committee on Nutritional Status during Pregnancy and Lactation, Food and Nutrition Board. Washington, D.C.: National Academy Press.

IOM (Institute of Medicine). 1998. Dietary Reference Intakes: Folate, Other B Vitamins, and Choline. Standing Committee on the Scientific Evaluation of Dietary Reference Intakes, Food and Nutrition Board. Washington, D.C.: National Academy Press.

Irwin, D.E., D.A. Savitz, I. Hertz-Picciotto, and K.A. St. André. 1994. The risk of pregnancy-induced hypertension: Black and white differences in a military population. Am. J. Public Health 84:1508–1510.


Keith, L., and B. Luke. 1991. The association between women's work, working conditions, and adverse pregnancy outcomes: A review of the literature and directions for future research. Women's Health Issues 1:113–119.

Keppel, K.G., and S.M. Taffel. 1993. Pregnancy-related weight gain and retention: Implications of the 1990 Institute of Medicine guidelines. Am. J. Public Health 83:1100–1103.


Lederman, S.A. 1993. The effect of pregnancy weight gain on later obesity. Obstet. Gynecol. 82:148–155.

Lotgering, F.K., M.B. van Doorn, P.C. Struijk, J. Pool, and H.C.S. Wallenburg. 1991. Maximal aerobic exercise in pregnant women: Heart rate, O2 consumption, CO2 production, and ventilation. J. Appl. Physiol. 70:1016–1023.

Louder, D.S., and B.A. Yoder. 1997. Factors associated with mothers' feeding intentions [manuscript]. Lackland Air Force Base, Tx.: 59th Medical Wing, Wilford Hall Medical Center.

Lovelady, C.A., B. Lonnerdal, and K.G. Dewey. 1990. Lactation performance of exercising women. Am. J. Clin. Nutr. 52:103–109.

Luke, B., N. Mamelle, L. Keith, F. Munoz, J. Minogue, E. Papiernik, and T.R. Johnson. 1995. The association between occupational factors and preterm birth: A United States nurses' study. Research Committee of the Association of Women's Health, Obstetric, and Neonatal Nurses. Am. J. Obstet. Gynecol. 173(pt. 1):849–862.

Lyons, T.J. 1992. Women in the fast jet cockpit—Aeromedical considerations. Aviat. Space Environ. Med. 63:809–818.


Magann, E.F., and T.E. Nolan. 1991. Pregnancy outcome in an active-duty population. Obstet Gynecol. 78:391–393.

Magann, E.F., M.I. Winchester, D.P. Carter, J.N. Martin Jr., J.D. Bass, and J.C. Morrison. 1995a. Factors adversely affecting pregnancy outcome in the military. Am. J. Perinatol. 12:462–466.

Magann, E.F., M.I. Winchester, S.P. Chauhan, T.E. Nolan, J.C. Morrison, and J.N. Martin Jr. 1995b. Marital status and military occupational specialty: Neither factor has a selective adverse effect on pregnancy outcome. J. Perinatol. 15:372–374.

Magann, E.F., M.I. Winchester, D.P. Carter, J.N. Martin Jr., T.E. Nolan, and J.C. Morrison. 1996. Military pregnancies and adverse perinatal outcome. Int. J. Gynecol. Obstet. 52:19–24.

Mamelle, N., B. Laumon, and O. Lazar. 1984. Prematurity and occupational activity during pregnancy. Am. J. Epidem. 119:309–322.

Manning-Dalton, C., and L.H. Allen. 1983. The effects of lactation on energy and protein consumption, postpartum weight change and body composition of well-nourished North American women. Nutr. Res. 3:293–308.

Suggested Citation:"6 Pregnancy and Lactation and Postpartum Return-To-Duty Fitness." Institute of Medicine. 1998. Assessing Readiness in Military Women: The Relationship of Body, Composition, Nutrition, and Health. Washington, DC: The National Academies Press. doi: 10.17226/6104.
×

McMurray, R.G., A.C. Hackney, V.L. Katz, M. Gall, and W.J. Watson. 1991. Pregnancy-induced changes in the maximal physiological responses during swimming. J. Appl. Physiol. 71:1454–1459.

MCO (Marine Corps Order) 5000.12D. 1995. See U.S. Department of the Navy, U.S. Marine Corps Headquarters, 1995.

Messersmith-Heroman, K., W.M. Heroman, and T.R. Moore. 1994. Pregnancy outcome in military and civilian women . Mil. Med. 159:577–579.

Muscati, S.K., K.G. Koski, and K. Gray-Donald. 1996. Increased energy intake in pregnant smokers does not prevent human fetal growth retardation. J. Nutr. 126:2984–2989.

Naismith, D.J., and C.D. Ritchie. 1975. The effect of breastfeeding and artificial feeding on body weights, skinfold measurements, and food intakes of forty-two primiparous women. Proc. Nutr. Soc. 34:116A–117A.

Nommsen, L.A., C.A. Lovelady, M.J. Heining, B. Lonnerdal, and K.G. Dewey. 1991. Determinants of energy, protein, lipid, and lactose concentrations in human milk during the first 12 months of lactation: The DARLING Study. Am. J. Clin. Nutr. 53:457–465.


Öhlin, A., and S. Rössner. 1990. Maternal body weight development after pregnancy. Int. J. Obes. 14:159–173.

OPNAVINST (Naval Operations Instruction) 6000.1A. 1989. See U.S. Department of the Navy, Office of the Chief of Naval Operations, 1989.


Parham, E.S., M.F. Astrom, and S.H. King. 1990. The association of pregnancy weight gain with the mother's postpartum weight. J. Am. Diet. Assoc. 90:550–554.

Parker, J., and B. Abrams. 1992. Prenatal weight gain advice: An examination of the recent prenatal weight gain recommendations of the Institute of Medicine. Am. J. Obstet. Gynecol. 79:664–669.

Pivarnik, J.M., N.A. Ayres, M.B. Mauer, D.B. Cotton, B. Kirshon, and G.A. Dildy. 1993. Effects of maternal aerobic fitness on cardiorespiratory responses to exercise. Med. Sci. Sports Exerc. 25:993–998.


Ramirez, G., R.M. Grimes, J.F. Annegers, B.R. Davis, and C.H. Slater. 1990. Occupational physical activity and other risk factors for preterm birth among U.S. Army primigravidas. Am. J. Public Health 80:728–729.

Rowe, E.A. 1994. Enlisted women at sea: A quantitative analysis. Report AD-A278 684. Newport, R.I.: Naval War College.


Sady, M.A., B.B. Haydon, S.P. Sady, M.W. Carpenter, P.D. Thompson, and D.R. Coustan. 1990. Cardiovascular response to maximal cycle exercise during pregnancy and at two and seven months postpartum. Am. J. Obstet. Gynecol. 162:1181–1185.

Sady, S.P., M.W. Carpenter, M.A. Sady, B. Haydon, B. Hoegsberg, E.M. Cullinane, P.D. Thompson, and D.R. Coustan. 1988. Prediction of VO 2max during cycle exercise in pregnant women. J. Appl. Physiol. 65:657–661.

Schauberger, C.W., B.L. Rooney, and L.M. Brimer. 1992. Factors that influence weight loss in the puerperium. Obstet. Gynecol. 79:424–429.

Siega-Riz, A., L. Adair, and C. Hobel. 1994. Institute of Medicine maternal weight gain recommendations and pregnancy outcome in a predominantly Hispanic population. Obstet. Gynecol. 84:565–573.

Sohlström, A., and E. Forsum. 1995. Changes in adipose tissue volume and distribution during reproduction in Swedish women as assessed by magnetic resonance imaging. Am. J. Clin. Nutr. 61:287–295.

South-Paul, J.E., K.R. Rajagopal, and M.F. Tenholder. 1992. Exercise responses prior to pregnancy and in the postpartum state. Med. Sci. Sports Exerc. 24:410–414.

Sternfeld, B., C.P. Quesenberry Jr., B. Eskenazi, and L.A. Newman. 1995. Exercise during pregnancy and pregnancy outcome. Med. Sci. Sports Exerc. 27:634–640.


Thomas, M.D., P.J. Thomas, and V. McClintock. 1991. Pregnant enlisted women in Navy work centers. Report No. TN-91-5. San Diego, Calif.: Navy Personnel Research and Development Center.

Suggested Citation:"6 Pregnancy and Lactation and Postpartum Return-To-Duty Fitness." Institute of Medicine. 1998. Assessing Readiness in Military Women: The Relationship of Body, Composition, Nutrition, and Health. Washington, DC: The National Academies Press. doi: 10.17226/6104.
×

Thomas, P.J. 1996. Psychosocial and Behavioral Correlates of Pregnancy Aboard Navy Ships. Paper presented at the Women's Research and Education Institute's Women in Uniform Conference. 10 December 1996. Washington, D.C.

Thomas, P.J., and J.E. Edwards. 1989. Incidence of pregnancy and single parenthood among enlisted personnel in the Navy. Report No. TR 90-1. San Diego, Calif.: Navy Personnel Research and Development Center.

Thomas, P.J., and M.D. Thomas. 1992. Impact of pregnant women and single parents upon Navy personnel systems. Report No. TN-92-8. San Diego, Calif.: Navy Personnel Research and Development Center.

Thomas, P.J., M.D. Thomas, and P. Robertson. 1993. Absence of Navy enlisted personnel: A search for gender differences. Report No. TR-93-3. San Diego, Calif.: Naval Personnel Research and Development Center.

U.S. Department of Defense. 1991. Department of Defense Directive 1315.7. ''Military Personnel Assignments." Washington, D.C.

U.S. Department of the Air Force. 1994. Air Force Instruction 40-502. "The Weight Management Program." November 7. Washington, D.C.

U.S. Department of the Air Force. 1996. Air Force Instruction 44-102. "Patient Care and Management of Clinical Services." February 1. Washington, D.C.

U.S. Department of the Army. 1992. Field Manual 21-20. "Physical Fitness Training." September 30. Washington, D.C.

U.S. Department of the Army. 1995. Army Regulation 40-501. "Standards of Medical Fitness." August 30. Washington, D.C.

U.S. Department of the Navy, Office of the Chief of Naval Operations. 1989. Naval Operations Instruction 6000.1A. "Management of Pregnant Women." February 21. Washington, D.C.

U.S. Department of the Navy, U.S. Marine Corps Headquarters. 1995. Marine Corps Order 5000.12D. "Marine Corps Policy on Pregnancy and Parenthood." October 4. Washington, D.C.


Ventura, S.J., K.D. Peters, J.A. Martin, and J.D. Maurer. 1997. Births and deaths: United States, 1996. Monthly Vital Statistics Report 46(1, suppl. 2). Hyattsville, Md.: National Center for Health Statistics.

Verdugo, N. 1996. Overview of the military woman. Presentation at the workshop on Assessing Readiness in Military Woman: The Relationship to Nutrition. September 9–10, Irvine, Calif.


Wallace, J.P., G. Inbar, and K. Ernsthaüsen. 1992. Infant acceptance of postexercise breastmilk. Pediatrics 89:1245–1247.

Webb, K.A., W.A. Wolfe, and M.J. McGrath. 1994. Effects of acute and chronic maternal exercise on fetal heart rate. J. Appl. Physiol. 77:2207–2213.

Westphal, K.A., K.E. Friedl, M.A. Sharp, N. King, T.R. Kramer, K.L. Reynolds, and L.J. Marchitelli. 1995. Health, performance, and nutritional status of U.S. Army women during basic combat training. Technical Report No. T96-2. Natick, Mass.: U.S. Army Research Institute of Environmental Medicine.

Winn, H.N., O. Hess., I. Goldstein, F. Wackers, and J.C. Hobbins. 1994. Fetal responses to maternal exercise: Effect on fetal breathing and body movement. Am. J. Perinatol. 11:263–266.

Suggested Citation:"6 Pregnancy and Lactation and Postpartum Return-To-Duty Fitness." Institute of Medicine. 1998. Assessing Readiness in Military Women: The Relationship of Body, Composition, Nutrition, and Health. Washington, DC: The National Academies Press. doi: 10.17226/6104.
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Suggested Citation:"6 Pregnancy and Lactation and Postpartum Return-To-Duty Fitness." Institute of Medicine. 1998. Assessing Readiness in Military Women: The Relationship of Body, Composition, Nutrition, and Health. Washington, DC: The National Academies Press. doi: 10.17226/6104.
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Suggested Citation:"6 Pregnancy and Lactation and Postpartum Return-To-Duty Fitness." Institute of Medicine. 1998. Assessing Readiness in Military Women: The Relationship of Body, Composition, Nutrition, and Health. Washington, DC: The National Academies Press. doi: 10.17226/6104.
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Suggested Citation:"6 Pregnancy and Lactation and Postpartum Return-To-Duty Fitness." Institute of Medicine. 1998. Assessing Readiness in Military Women: The Relationship of Body, Composition, Nutrition, and Health. Washington, DC: The National Academies Press. doi: 10.17226/6104.
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Suggested Citation:"6 Pregnancy and Lactation and Postpartum Return-To-Duty Fitness." Institute of Medicine. 1998. Assessing Readiness in Military Women: The Relationship of Body, Composition, Nutrition, and Health. Washington, DC: The National Academies Press. doi: 10.17226/6104.
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Suggested Citation:"6 Pregnancy and Lactation and Postpartum Return-To-Duty Fitness." Institute of Medicine. 1998. Assessing Readiness in Military Women: The Relationship of Body, Composition, Nutrition, and Health. Washington, DC: The National Academies Press. doi: 10.17226/6104.
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Suggested Citation:"6 Pregnancy and Lactation and Postpartum Return-To-Duty Fitness." Institute of Medicine. 1998. Assessing Readiness in Military Women: The Relationship of Body, Composition, Nutrition, and Health. Washington, DC: The National Academies Press. doi: 10.17226/6104.
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Suggested Citation:"6 Pregnancy and Lactation and Postpartum Return-To-Duty Fitness." Institute of Medicine. 1998. Assessing Readiness in Military Women: The Relationship of Body, Composition, Nutrition, and Health. Washington, DC: The National Academies Press. doi: 10.17226/6104.
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Suggested Citation:"6 Pregnancy and Lactation and Postpartum Return-To-Duty Fitness." Institute of Medicine. 1998. Assessing Readiness in Military Women: The Relationship of Body, Composition, Nutrition, and Health. Washington, DC: The National Academies Press. doi: 10.17226/6104.
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Suggested Citation:"6 Pregnancy and Lactation and Postpartum Return-To-Duty Fitness." Institute of Medicine. 1998. Assessing Readiness in Military Women: The Relationship of Body, Composition, Nutrition, and Health. Washington, DC: The National Academies Press. doi: 10.17226/6104.
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Suggested Citation:"6 Pregnancy and Lactation and Postpartum Return-To-Duty Fitness." Institute of Medicine. 1998. Assessing Readiness in Military Women: The Relationship of Body, Composition, Nutrition, and Health. Washington, DC: The National Academies Press. doi: 10.17226/6104.
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Suggested Citation:"6 Pregnancy and Lactation and Postpartum Return-To-Duty Fitness." Institute of Medicine. 1998. Assessing Readiness in Military Women: The Relationship of Body, Composition, Nutrition, and Health. Washington, DC: The National Academies Press. doi: 10.17226/6104.
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Suggested Citation:"6 Pregnancy and Lactation and Postpartum Return-To-Duty Fitness." Institute of Medicine. 1998. Assessing Readiness in Military Women: The Relationship of Body, Composition, Nutrition, and Health. Washington, DC: The National Academies Press. doi: 10.17226/6104.
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Suggested Citation:"6 Pregnancy and Lactation and Postpartum Return-To-Duty Fitness." Institute of Medicine. 1998. Assessing Readiness in Military Women: The Relationship of Body, Composition, Nutrition, and Health. Washington, DC: The National Academies Press. doi: 10.17226/6104.
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Suggested Citation:"6 Pregnancy and Lactation and Postpartum Return-To-Duty Fitness." Institute of Medicine. 1998. Assessing Readiness in Military Women: The Relationship of Body, Composition, Nutrition, and Health. Washington, DC: The National Academies Press. doi: 10.17226/6104.
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Page 154
Suggested Citation:"6 Pregnancy and Lactation and Postpartum Return-To-Duty Fitness." Institute of Medicine. 1998. Assessing Readiness in Military Women: The Relationship of Body, Composition, Nutrition, and Health. Washington, DC: The National Academies Press. doi: 10.17226/6104.
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Suggested Citation:"6 Pregnancy and Lactation and Postpartum Return-To-Duty Fitness." Institute of Medicine. 1998. Assessing Readiness in Military Women: The Relationship of Body, Composition, Nutrition, and Health. Washington, DC: The National Academies Press. doi: 10.17226/6104.
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Next: 7 Conclusions and Recommendations »
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U.S. military personnel are required to adhere to standards of body composition, fitness, and appearance to achieve and maintain readiness—that is, the maintenance of optimum health and performance so they are ready for deployment at any moment. In 1992, the Committee on Military Nutrition Research reviewed the existing standards and found, among other things, that the standards for body composition required for women to achieve an appearance goal seemed to conflict with those necessary to ensure the ability to perform many types of military tasks. This report addresses that conflict, and reviews and makes recommendations about current policies governing body composition and fitness, as well as postpartum return-to-duty standards, Military Recommended Dietary Allowances, and physical activity and nutritional practices of military women to determine their individual and collective impact on the health, fitness, and readiness of active-duty women.

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