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



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--> 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

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--> 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

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--> 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.

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--> 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).

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--> 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

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--> 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).

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--> 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).

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--> 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

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--> 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

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--> 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

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--> 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).

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--> 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

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--> 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

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--> 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.

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--> 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.

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--> 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).

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--> 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.

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--> 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.

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--> 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.

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--> 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.

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--> 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.

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