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OCR for page 96
Total Amount and
Pattern of Weight Gain:
Physiologic and Maternal Determinants
Total weight change during pregnancy can vary from a weight loss to
a gain of more than 30 kg (66 lb). This wide variation in gain among
healthy pregnant women appears to be attributable to several physiologic
and environmental factors. For example, changes in the secretion of mater-
nal hormones and other physiologic adjustments associated with pregnancy
undoubtedly affect the utilization of energy sources and thus the amount
of weight gained. Certain maternal characteristics and health habits may
also exert an influence. In this chapter, the subcommittee reviews these
physiologic factors and evaluates the relationship between selected mater-
nal characteristics and the amount and pattern of gain. A discussion of
relationships between dietary- and supplemental energy intake and weight
gain is found in Chapter 7.
NORMS FOR TOTAL GAIN, RATE OF GAIN, ANI)
COMPOSITION OF GAIN
Pattern and Amount of Gain
In 1971, Hytten and Leitch established physiologic norms for total
weight gain, the rate of gain in the last half of pregnancy, and the rate of
gain associated with the best reproductive performance. Using data from
two British studies (Humphreys, 1954; Thomson and Billewicz, 1957) of
more than 3,800 women, they concluded that the physiologic average total
gain of "healthy primigravidae women eating without restriction" is 12.5
96
OCR for page 97
TOTAL AMOUNT AND PATTERN OF WEIGHT GAIN
28
12
10
8
4
2
A 24
_ ,_
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_ ~
Be 16
_ ~
~ 12
-A 8
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-A 4
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8 12 16 20 24 28 32 36 40
Week of Gestation
97
FIGURE 5-1 Mean rate of weight gain during pregnancr of 2,868 nonnotensive, pnmi-
gravid women, from Thomson and Billewicz (1957) by permission of Blackwell Scientific
Publications, Inc.
kg (27.5 lb) approximately 1 kg (2.2 lb) in the first trimester and the
remainder during the last two trimesters. For multigravid women, they
made no specific estimates but suggested that a slightly lower gain could
be expected.
1b determine a physiologic norm for rate of gain during the last half
of pregnancy, Hytten and Leitch (1971) extracted weight gain data from
records maintained by the Aberdeen Maternity Hospital for 486 healthy
women aged 20 to 29 and at least 160 cm (63 in.) tall, who delivered
their infants between weeks 39 and 41 of pregnancy (between 1950 and
1955). No attempt was made to control weight gain by food restriction in
this population. The most common value for the rate of gain during the
last half of pregnancy was between 0.41 and 0.45 kg (~1 lb) per week,
but the range of gain was very wide from less than 0.1 to 0.9 kg (0.2
to 2 lb) per week. The data from this study are shown in Figure 5-1,
which has been used widely to evaluate the rate and total amount of weight
gained by pregnant woman. Hytten and Leitch emphasized, however, that
considerable variation of this pattern is consistent with good pregnancy
outcomes. The lowest incidence of preeclampsia, low birth weight, and
perinatal death was associated with gaining 0.45 kgAveek during the last 20
weeks of pregnancy. The following rates were established for each quarter
of pregnancy among primigravid women:
OCR for page 98
98
NUTRITIONAL STATUS AND WEIGHT GAIN
O to 10 weeks, 0.065 kg~week
10 lo 20 weeks, 0.335 kgh~eek
20 to 30 weeks, 0.450 kg/week
30 to 40 weeks, 0.335 kg/week
Components of Gain
The components of gain can be divided into two parts the products
of conception and maternal tissue accretion. The products of conception
comprise the fetus, placenta, and amniotic fluid. On the average, the fetus
represents approximately 25% of the total gain, the placenta about 5%, and
the amniotic fluid about 6% (Hytten, 1980b). Cross-sectional data indicate
that fetal growth follows a sigmoid curve, with growth slowing in the final
week of gestation. The rate of placental growth declines toward the end of
pregnancy.
Expansion of maternal tissues accounts for approximately two-thirds
of the total gain. In addition to increases in uterine and mammary tissue
mass, there is an expansion of maternal blood volume, extracellular fluid,
fat stores, and possibly other tissues. In laboratory animals, an increase in
liver and intestinal mucosal mass during gestation is evident, but there is
no evidence that these tissues increase in pregnant women.
Expansion of the blood volume accounts for 10% of the total gain.
The increase in plasma volume (approximately 50%) is greater than that of
the red blood cell mass increase, but expansion of both is related to fetal
size (Hytten, 1980b). Most of the increase in plasma volume occurs before
week 34 of gestation; the increase in red blood cell mass is believed to be
linear from the end of the first trimester to term. Iron supplementation
increases the expansion of the red blood cell mass (see Chapter 14~.
In women without generalized edema or with only leg edema, an
expansion of the extracellular, extravascular fluid volume accounts for
approximately 13% of the total gain. The retention of extracellular fluid
can be highly variable; some women accumulate more than 5 liters (5
kg, or 11 lb). The physiologic basis for extracellular fluid retention is
uncertain. Placental estrogens may increase the affinity for water of muco-
or glycopolysaccharides in connective tissue (Hytten, 1980b), resulting in
an expanded, softer tissue.
Women normally accumulate fat during pregnancy. Hytten (1980b)
estimated that pregnant women who gain 12.5 kg (27.5 lb) without edema
acquire about 3.5 kg (7.5 lb) of fat. (See Chapter 6 for other, more
recent estimates.) The purpose of the fat store is uncertain: it may be
a maternal energy reserve for use when the food supply is limited during
either pregnancy or lactation.
OCR for page 99
TOTAL AMOUNT AND PATTERN OF WEIGHT GAIN
14
12
10
y
~8
._
._
4
2
0 10 20
Week of Gestation
Water
6
Fat
_
. _
Protein
30 40
FIGURE 5-2 Composition of weight gain during pregnancy. From Hytten (1980b).
Proximate Composition of Gain
99
Hytten (1980b) estimated that, on average, water contributes approx-
imately 62% of the total gain at term, fat contributes 30%, and protein
contributes 8%; but there is considerable variation in these values. Of the
total fat gain, 90% is deposited as maternal stores. About 60% of the total
protein accretion is located in the products of conception; the remainder is
accounted for by the gain of maternal uterine, mammary, and blood tissues.
In early nitrogen balance studies, reported protein retentions were higher
than could be accounted for by those fetal and maternal tissues. How-
ever, recent studies conducted in metabolic wards have reported protein
retentions comparable to the estimated need for pregnancy.
Weight gain attributable to body water is the most variable of the
components. A reported positive relationship between the increased total
body water and infant birth weight (Hytten, 1980b) suggests that water
accumulation is beneficial. An estimate of the pattern of weight composition
for each quarter of pregnancy is depicted in Figure 5-2. Variation in the
composition of gain is discussed in Chapter 6.
TOTAL WEIGHT GAIN ACID PATTERN OF GAIN
The most representative data for total weight gain in the U.S. pop-
ulation are from the 1980 National Natality Survey (NNS) (TaRel, 1986),
which is a probability sample of all live births to U.S. women in 1980.
Because of the limited amount of information available from published
OCR for page 100
100
NUTRITIONAL STATUS AND WEIGHT GAIN
reports, the subcommittee relied heavily on the data from the 1980 NNS
to determine the independent effects of maternal characteristics on to-
tal weight gain (Kleinman, 1990; Duffel, 1986~. The distribution of gains
among white, non-Hispanic, married mothers by body mass index (BMI)
(Kleinman, 1990) is shown in Figure 5-3 and Table 5-1.
Data from 12 other studies on gestational weight gain are shown in
Table 5-2. These studies were selected because they provided data on
cumulative increase in maternal weight at various times during pregnancy,
thus permitting weight gain patterns to be estimated. These data were
obtained from six countries and cover a span from 1925 to 1982. Three
of the studies (Brown et al., 1986; Husaini et al., 1986; Kawakami et al.,
1977) were reported after release of the Food and Nutrition Board's report,
Maternal Nutrition and the Course of Pregnancy (NRC, 1970~. The study by
Brown et al. (1986) provides the most recent data regarding women living
in the United States. Reported average total gains ranged from 10.1 to
14.9 kg (22 to 33 lb) across samples in these studies. From the published
data, it is extremely difficult to identify a physiologic norm for total weight
. .
gain c unng pregnancy.
In the studies summarized in liable 5-2, women were weighed when
they entered prenatal care (at 13 or 16 weeks of gestation), then usually
once per month until about week 30 of gestation, and more frequently
after that. Weight change at specific weeks of gestation was observed
or interpolated from these data. In most studies, weight change was
based on measured weight at the first visit; in others, it was based on
recalled prepregnancy weight. Few studies collected data on weight gain
during the first trimester. Most of them excluded women with obvious
pregnancy complications, but some studies provided few descriptive data
about their samples. Problematic characteristics of some studies include
prescribed weight restriction, limitations of samples to poor women, and a
complete lack of information about sample selection. Infant birth weight, an
important criterion for healthy pregnancy outcome, was rarely considered.
Not only did total weight gain differ among studies, as mentioned
above, but there were also differences in the amount of weight gained at
specific points during gestation (liable 5-2~. In the study by Brown et al.
(1986), mean weight gains were higher at each gestational period. Patterns
of gain are illustrated in Figure 5-4, which shows the cumulative gain
reported in the 12 studies, and in Figure 5-5, which provides data from
selected studies of well-nourished women with uncomplicated pregnancies
in the United States and the United Kingdom.
Although the study designs and populations differed among these
studies, the slopes of the lines representing cumulative weight gains were
quite similar. As mentioned above, Hytten and Leitch (1971) suggested a
gain of 0.41 to 0.45 kg (~1 lb) per week as a reference for the last half of
OCR for page 101
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OCR for page 102
102
NUTRITIONAL STATUS AND WEIGHT GAIN
TABLE 5-1 Mean Total Weight Gain and Coefficient of Variation for
White, non-Hispanic, Married Mothers Delivering Live Infantsa
Weight Gain,
kg, by
BMI Number in Mean Weight Coefficient of Percentile
Group Sample Gain, kg Variation, % 15th 85th
Low 1,027 13.8 37 8.6 18.2
(<19.8)
Moderate 2,393 13.8 38 7.7 18.6
(19.~26.0)
High 246 12.4 48 6.4 17.3
(26.1-29.0)
Very high 280 8.7 97 0.5 16.4
(>29.0)
Total 3,946 13.3 45 8.2 17.7
a Based on unpublished data from 1980 National Natality Survey.
pregnancy. Similarly, Thomson and Billewicz (1957) concluded from their
study of 2,868 normotensive Scottish primigravid women that an average
gain of about 0.45 kg (1 lb) per week during the second half of pregnancy
was a "sound and realistic average to aim at" (p. 247). Rates of gain
observed by Thomson and Billewicz (1957) were 0.467 kglweek (standard
deviation iSD] = 0.161) between 20 and 30 weeks of gestation and 0.395
kg/week (SD = 0.213) during weeks 30 to 36. Reported rates of gain of
U.S. women during the same time period were lower than those observed
in the United Kingdom (Robinson et al., 1943; 1bmpkins and Wiehl, 1951).
Robinson and coworkers stressed that normal and overweight patients were
told to limit their intake of carbohydrates and fat. The highest rate of gain
occurred during the seventh lunar month of gestation (Robinson et al.,
1943); between 20 and 28 weeks of gestation, the rate of gain averaged
approximately 0.455 kg (1 lb) per week.
Only four reports of the rate of gain have appeared since 1971. In a
1977 study of weekly weights of 2,000 pregnant Japanese women, the mean
rate of gain was 0.45 kg (1.0 lb) per week between 16 and 24 weeks and 0.48
kg/week between 24 and 32 weeks of gestation (Kawakami et al., 1977).
Meserole and colleagues (1984) constructed a graph of the weight gain
pattern of 80 pregnant girls aged 19 or less. The slope of the rate of gain
for the adolescents was described as steeper than that for adult pregnant
women. In a study of 1,000 pregnant women in Indonesia (Husaini et al.,
1986), the rate of gain and total gain were lower than those reported in the
other studies. The mean prepregnangy weight for the Indonesian women
was 44.5 kg (98 lb), substantially less than that of women in the United
OCR for page 103
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OCR for page 105
TOTAL AMOUNT AND PATTERN OF WEIGHT GAIN
20
18
16
>`
~5
cn 14
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105
Cummings, 1934
· Stander and Pastors, 1940
Kuo, 1941
· ~Robinson et al., 1943
~Scott and Benjamin, 1948
_~ Tompkins et al., 1951
~ Thomson and Billewicz, 1957
{ - Hymen and Leitch, 1971
· Venkatachalam et al., 1960
t Kawakamj et al., 1977
Brown et al., 1986
_~ Husaini et al., 1986
1 92~1 932
1 932-1 940
1934 1 940
1 943
1941 -1 944
1 947-1 949
1949- 1 954
1950 1955
1 960
1 977
1979- 1 982
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14 16 18 20 22 24 26 28 30 32 34 36 38 40
Week of Gestation
FIGURE 54 Pattern of maternal weight gain shown by data from 12 studies.
States. Brown and coworkers (1986) studied the pattern of gain of 459 low-
income women who delivered infants weighing between 3,000 and 4,500 g.
The weekly rates of maternal weight gain by this group were higher during
the first two trimesters than has been reported in other studies (Table S-2),
namely, 0.22 kg (O.S lb) per week during the first trimester and 0.52 kg
(1.1 lb) per week during the second trimester, but they were comparable
(0.40 kg, or 0.9 lb, per week) during the third trimester. A slowing of
weight gain or a slight weight loss has been consistently reported as women
approached term (Cummings, 1934; Kuo, 1941; Robinson et al., 1943; Scott
and Benjamin, 1948~.
Few investigators have evaluated weight gain during the first trimester
in detail. Clapp et al. (1988) weighed 20 physically active, well-nourished
women serially from before conception to week IS of gestation and showed
OCR for page 106
106
NUTRITIONAL STUDIOUS AND WEIGHT GAIN
· Cummings, 1934 (192~1932)
14 - ~Stander and Pastore, 1940 (1932-1940)
---{O Scon and Benjamin, 1948 (1941 -1944)
Tompkins and V~ehl, 1951 (1947-1949)
· Thomson and Billewicz, 1957 (1949-1954)
· Hymen and Leitch, 1971 (1950-1955)
Brown et al., 1986 (197~1982
8
4
2
o
/
///
To/
At/
q :
/
1 1 1 1 1 1 1 1 1 1
i'
//
10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40
Week of Gestation
FIGURE 5-5 Pattern of maternal weight gain shown by the six studies in Figure 5-4 that
focused on well-nounshed women in Europe and the United States who had uncomplicated
pregnancies.
that maternal gain averaged 2 kg (4.5 lb) at 7 weeks and 4.3 kg (9.5 lb) at
15 weeks; the average rate of gain from 0 to IS weeks of gestation was 0.29
kg, or 0.6 lb, per week. Weights beyond this period were not given.
Thomson and Billewicz (1957) reported that 40% of their population
gained their suggested amount of 3.6 to 5.4 kg (8 to 12 lb) during the
second trimester, whereas almost 25% gained less. The investigators did
not relate the pattern of gain to pregnancy outcome. However, only 14% of
their sample gained amounts within the ranges the investigators considered
to be ideal for both the second and third trimesters. Thus, the individual
experience of many pregnant women is unlikely to fit the pattern depicted
in Figure S-1.
OCR for page 110
110
NUTRITIONAL STATUS AND WEIGHT GAIN
TABLE 5-3 Gestational Weight Gain Reported by Maternal
Prepregnancy Weight-for-Height Status in Different Studies of U.S.
Women
Number Total
Prepregnancyin Mean Coefficient of
Weight for HeightSample Gain, kg Variation, % Reference
Very low (<80% of 155 12.6 29 Brown et al., 1981
standard a or 79 9.3 34 Mitchell and Lerner, 1989
BMIb ~ 16.5)
Low (8~90~o of 243 12.9 36 Brown et al., 1981
standard or BMI 105 11.2 37 Winikoff and Debrovner, 1981
16.5-19.8) 62 11.7 71 Rosso, 1985
268 14.3 31 Abrams and Laros, 1986
80 14.3 NRC Brown et al., 1986
21 15.5 NR Haiek and Lederman, 1989
283 9.3 33 Mitchell and Lerner, 1989
Normal (9~120~o of 301 ll.Od 31 Gormican et al., 1980
standard or BMI 247 12.6 63 Brown et al., 1981
> 19.~26) 106 10.4 32 Winikoff and Debrovner, 1981
35 12.6 33 George et al., 1984
137 10.4 61 Rosso, 1985
1,535 15.2 31 Abrams and Laros, 1986
174 13.9 NR Brown et al., 1986
868 14.4 39 Muscati et al., 1988
39 15.8 NR Haiek and Lederman, 1989
362 8.4 37 Mitchell and Lerner, 1989
High (12~135% of 901 15.2 35 Abrams and Laros, 1986
standard or BMI
> 2~29)
Very high (>135% 224 14.1 55 Abrams and Laros, 1986
of standard or 68 ~9.7 NR Brown et al., 1986
BMI > 29)
a Standards varied among the studies. Weight-for-height tables from Metropolitan Life
Insurance Company (1959) were used most commonly.
b BMI = body mass index, metric units.
c NR = Not reported.
d Weight gain for second and third trimesters only.
and Lerner (1989) found that the gain of women in the low and very
low weight-for-height groups was significantly greater than that of normal-
weight women (9.3 compared with 8.5 kg, or 20.5 versus 19 lb). Brown and
coworkers (1981) did not find any differences in gain between underweight
and normal-weight women. Abrams and Laros (1986) compared the weight
gain of women in low, normal, high, and very high weight-for-height groups.
No statistically significant differences in mean weight gain were found
among women in the four groups, but the total gain of women in the
OCR for page 111
TOTAL AMOUNT AND PATTERN OF WEIGHT GAIN
111
very overweight group tended to be slightly lower than that of women in
the normal and high groups (14.1 compared with 15.2 kg, or 31 versus
33 lb). These investigators noted that the gains of the women in the very
overweight category were more variable than those of women in the other
groups. Their coefficient of variation for gain was 55% compared with
about 31 to 35% in the other three groups. Among the very overweight
women in that study, there was a higher percentage of women with low
weight gains, which lowered the group average. The very overweight women
in this clinic were not told to limit their food intake or to restrict their
weight gain.
In these 10 studies, weight gain by women in each of the five groups
varied substantially (Table 5-3), and coefficients of variation of gain for
women with normal prepregnancy weights ranged from 31 to 63%. This
degree of variation in gain after controlling for differences in maternal body
size shows that maternal prepregnanc,, weight-for-height status accounts for
only a small part of the variation in weight gain.
An analysis of the 1980 NNS data (Kleinman, 1990, and Table 5-1)
showed that as maternal prepregnancy BMI increased from moderate to
very high, mean total weight gain fell by about 5 kg (11 lb), and the variation
in gain increased. More than 10% of the women in the very overweight
group lost weight during gestation, and more than one-third of the women
in that group met the criterion for low weight gain, i.e., a gain of less than
6.8 kg (15 lb). The proportion of women with a low total weight gain was
about four times greater among women in the very high BMI group than
among women in the low and moderate BMI groups. As shown in Figure 5-
3, only 25% of those with a low BMI, 20% of those with moderate and high
BMIs, and 13% of those with very high BMIs had weight gains close to the
gain suggested by Hytten and Leitch (1971), i.e., between 11.8 and 13.6 kg,
or 26 and 30 lb. The 1980 NNS study is compatible with the observations
of Abrams and Laros (1986) that the gains of very overweight women are
lower on average and are more variable than those of other women, but it
provided no evidence that underweight women were at an increased risk
of low weight gain. This is an interesting finding, and follow-up studies are
needed.
There are only a few studies of the effect of prepregnancy body weight
on the panem of weight gain. In one recent study, Meserole and coworkers
(1984) compared the pattern of gain of underweight, normal, or overweight
adolescents (total sample size, 80~. The only difference observed was a
gain by the normal-weight adolescents in the first trimester in comparison
with little or no gain by adolescents in the other two groups, but the
methods used to ensure the accuracy of the estimates of prepregnancy
weight, and thus of early weight gain, were not described. The rate of
gain by the normal-weight adolescents was slightly lower in the second and
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112
NUTRITIONAL STATUS AND WEIGHT GAIN
third trimesters than that of the underweight and overweight adolescents;
total weight gains did not differ. There was no further interpretation of
these data, and the differences in weight gain pattern were not tested
for significance. Results from studies conducted in the 1940s and 1950s
of the effect of prepregnancy weight for height on the rate of gain were
inconsistent (Robinson et al., 1943; Scott and Benjamin, 1948; Stander and
Pastore, 1940; Thomson and Billewicz, 1957~.
Maternal Height
In a comprehensive review of the literature, the subcommittee located
only one study (Kleinman, 1990) designed to determine whether there is an
independent effect of maternal height on total weight gain. In this study,
data from the 1980 NNS were analyzed by using multiple linear regression
techniques to control for BMI, age and parity, education level, alcohol use,
ethnic origin, and cigarette smoking; a significant effect of height on weight
gain was observed. Short women (<157 cm, or <62 in.) gained about 1
kg (2 lb) less, on average, than did taller women (>170 cm, or >67 in.),
but there was no evidence that short women had an increased risk of low
weight gain. An earlier study focused on the relationship between height
and the pattern of gain (Thomson and Billewicz, 1957), but no effect was
identified. The independent effect of stature on the amount and rate of
gain needs further investigation.
Ethnic Origin
Differences in the total amount of weight gained by black and white
women during gestation were first reported by Eastman and Jackson (1968)
in a study of clinic patients in Baltimore, Maryland, between 1954 and
1961. The total weight gain of the white women averaged 9.9 kg (21.8 lb),
whereas that of the black women averaged 9.0 kg (19.8 lb). The statistical
significance of this difference was not determined. The reported mean
weight gains of the women of both races was the same if the prepregnancy
weight was greater than 82 kg (180 lb). In two other large studies of
weight gain conducted in the 1950s and 1960s, no difference in weight gain
between black and white women was detected (Niswander and Jackson,
1974; Simpson et al., 1975~. Both black women and white women in
the Collaborative Perinatal Project gained an average of 9.9 kg (21.8 lb)
(Niswander and Jackson, 1974~. Similar gains were reported for black as
well as white wives of military men studied in San Antonio, Texas, between
1946 and 1966 (Simpson et al., 1975~. Multivariate analysis was not used
in either of these studies to determine whether there was a statistically
significant, independent effect of race on gestational weight gain.
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TOTAL AMOUNT AND PATTERN OF WEIGHT GAIN
113
More recent studies have focused on the effect of ethnic origin on
weight gain in populations including white, black, Southeast Asian, and
Hispanic women. In an obstetric clinic for teenagers in San Diego, Califor-
nia, there was no significant difference in the mean weight gain of white,
black, and Hispanic mothers (Felice et al., 1986~; but Hispanic mothers
tended to gain the most weight. In another study, Puerto Rican teenagers
in New Jersey gained significantly less than white or black teenagers did
(Scholl et al., 1988~. In Minnesota, Swenson et al. (1986) studied the
weight gains of white, black, Hmong (a Laotian tribe), and other Southeast
Asian pregnant adolescents and adults. The total gain of the Hmong and
the other Southeast Asian adolescents and adults was about 5 kg (11 lb)
less than that of their white and black counterparts. Different attitudes
about food practices during pregnancy among Southeast Asian women may
contribute to their lower weight gains.
The average weight gain of white women in the 1980 NNS was signifi-
cantly greater than that of black women (13.2 versus 12.2 kg, or 29.1 versus
26.8 lb) Duffel, 1986~. After controlling for the effects of prepregnancy
weight, marital status, education, and age combined with parity, white
women still gained about 0.5 kg more than black women did. The gesta-
tional period of white women tended to be about 0.5 week longer than that
of black women, but this difference only partly explained the higher gains
of the white women. The mean weight gain of married Hispanic women
and white women did not differ, but the risk of low weight gain was twice
as high in Hispanics as it was in whites. Black women also were at a 7055
greater risk for low levels of weight gain compared with whites.
In summary, a consistent effect of ethnic origin on gestational weight
gain is not apparent in the literature. Black women in the 1980 NNS gained
significantly less than white women did. Differences in the gestational
period did not account for all this difference. The effect of maternal ethnic
origin on the rate of weight gain has not been studied.
Age and Parity
There are many reports of weight gain and pregnancy outcome in
adolescent women, but most do not control for parity, prepregnangy weight
for height, gestational length, ethnic origin, or alcohol and tobacco con-
sumption when evaluating the effect of age on weight gain. The results
of nine studies of weight gain among adolescents published since 1970 are
summarized in Able 54. Adolescent mothers in Lima, Peru, gained from 1
to 7 kg (2 to 15 lb) less than U.S. adolescents on the average (Frisancho et
al., 1983), but the study is of value because of the large number of pregnant
teenagers of each year of age between 12 and 17. The mean weight gains of
the Peruvian teenagers between ages 14 and 17 did not differ. Only 28 girls
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114
NUTRITIONAL STATUS AND WEIGHT GAIN
TABLE 5-4 Effect of Chronological Maternal Age on Gestational Weight
Gain
Number in Weight Coefficient of
ReferenceAge, yr Sample Gain, kg Variation, %
Ancri et al., 197712-17 26 13.4 26
1~19 22 12.4 31
2~24 24 11.1 17
25-32 26 10.7 18
Frisancho et al., 198312-13 28 9.0 18
14 104 9.8 22
15 296 9.9 26
16 565 9.7 25
17 229 10.0 26
18-25 46 9.7 16
Horon et al., 1983<16 422 12.5 NRa
2(~24 422 12.5 NR
Loris et al., 198513-15.9 18 17.2 23
1~17.9 84 17.1 40
18-19.5 25 17.3 54
Meserole et al., 198413-15 24 14.5 32
1~17 25 17.9 35
Endres et al., 198515-18 46 12.0 NR
19-30 198 11.0 NR
Muscati et al., 19881~17 90 16.5 36
1~19 135 15.1 36
2~35 461 13.8 39
Scholl et al., 198816.9 + 1.3 (SD)b 696 14.7 39
Haiek and Lederman, 1989<16 90 14.6 NR
19-30 90 16.9 NR
a NR = Not reported.
b SD = Standard deviation.
were between the ages of 12 and 13, but these girls gained about 0.8 kg (1.8
lb) less than the older girls did. This difference was not tested for statistical
significance. No consistent relationship between maternal age and weight
gain was observed in the six studies of U.S. women. Three groups reported
that young mothers gained more weight (Ancri et al., 1977; Endres et al.,
1985; Muscati et al., 1988), two reported that young mothers gained less
weight (Haiek and Lederman 1989; Meserole et al., 1984), and two found
no difference (Horon et al., 1983; Loris et al., 1985~. One group reported
a relationship between gynecologic age and weight gain; immature girls
had lower gains than the more mature girls did (Meserole et al., 1984~.
This finding, plus the observation that 12- to 13-year-old Peruvian mothers
gained less weight (Frisancho et al., 1983), suggests that the weight gains of
very young adolescents (<2 years after menarche) may be lower than those
of older adolescents. Further research is needed to confirm this conclusion.
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TOTAL AMOUNT AND PATTERN OF WEIGH GAIN
115
Multiple linear regression analysis was used to evaluate the effect of
age and parity on weight gain among women who participated in the 1980
NNS (Kleinman, 1990~. Primiparous women lit all age groups gained about
1 kg (2 lb) more than multiparous women of the same age did, and the risk
of low weight gains was about one-third lower among primiparous women.
After controlling for parity, differences in weight gain by age were small.
Primiparous women of all ages gained more (about 1 kg, or 2 lb) than
multiparous women of the same age.
In summary, the limited data suggest that very young mothers have
lower gains than other women do. The effect of pregnancy after age 35 or
40 on gestational weight gain has not been studied. Thomson and Billewicz
(1957) studied the relationship between maternal age and the pattern of
weight gain, and no relationship was found.
Cigarette Smoking
Results of multivariate analysis showed that the mean weight gain
of married smokers and nonsmokers in the 1980 NNS were similar, but
mothers who smoked cigarettes were 50% likelier to gain less than 6.8
kg (15 lb) than were nonsmoking mothers. Rush (1974) and Davies et
al. (1976) reported that female nonsmokers gain less weight than female
smokers do, but other investigators have not found this effect (Carruth,
1981; Meyer, 1978; Picone et al., 1982~. It appears that smoking has a
small effect, if any, on mean gestational weight gain but a larger effect on
risk of low weight gain.
Alcohol and Illegal Substances
There are many reports on the effect of maternal alcohol consumption
on fetal growth and development, but few on the relationship between
alcohol consumption and gestational weight gain. In a study of 204 alcohol
abusers and 11,123 alcohol nonabusers (Sokol et al., 1980), no differences
were found in maternal prepregnancy weight, height, or gestational weight
gain between the two groups. In another study of 270 pregnant women
(Tennes and Blackard, 1980), there was no correlation between alcohol use
and gestational weight gain. In the 1980 NNS (Kleinman, 1990), alcohol
consumption was found to have little effect on mean weight gain. Mean
weight gain of moderate users of alcohol (defined as those who drank more
than once per month or more than two drinks per drinking occasion) was
0.2 kg (0.4 lb) higher than that of women who consumed no alcohol. The
risk of low weight gain was greatest among the nondrinkers.
In a thorough review of the literature, the subcommittee found only
one study (Zuckerman et al., 1989) on the relationship between the use
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116
NUTRITIONAL STATUS AND WEIGHT GAIN
of cocaine and marijuana and gestational weight gain. In that study,
Zuckerman et al. (1989) compared 202 marijuana users with 895 nonusers
and 114 cocaine users with 1,010 nonusers among women attending the
prenatal clinic at Boston City Hospital. The mean weight gain of marijuana
users was 12.7 kg (28 lb) compared with 14.1 kg (31 lb) for nonusers. The
mean gain of cocaine users was 10.5 kg (23 lb) compared with 14.1 kg
(31 lb) for nonusers. The use of these substances and other illicit drugs
generally is associated with a life-style that is not supportive of good eating
and health habits. Therefore, it is not surprising that these women had
lower mean weight gains during pregnancy.
Socioeconomic Status
Information about family income was requested on questionnaires
that were sent to married mothers in the 1980 NNS (Taffel, 1986~. In a
bivariate analysis, women from households with incomes above $30,000 per
year gained 0.6 kg (1.4 lb) more than did women from households with
incomes of less than $9,000 per year. The risk of low weight gain increased
nearly twofold as annual household income fell from $30,000 to $9,000.
However, these results were not statistically controlled for other variables
that could influence weight gain.
Marital status is also linked with socioeconomic status since female-
headed households tend to have lower household incomes. On the average,
married mothers gained about 1 kg more than unmarried mothers did
(Taffel, 1986~.
Data on the educational attainment of both married and unmarried
mothers were analyzed in the multiple linear regression described by Klein-
man (1990~. Mean weight gain was similar for women in all educational
groups, but compared with mothers with 13 or more years of education,
the risk of low weight gain was 50% higher among mothers with <12 years
of education and 25% higher among those with 12 years of education.
Work or Physical Activity
Studies on the effect of heavy work or physical activity on weight gain
should be interpreted with caution, because high energy expenditure can
be offset by increases in energy intake so that energy balance is maintained.
Also, it is difficult to determine whether the stress (both physical and
psychologic) of work, instead of the increased energy expenditure, may
have led to reduced weight gain. Some investigators have reported an
elevated risk of preterm delivery among working women (Mamelle and
Munoz, 1987; Mamelle et al., 1984), whereas others have failed to identify
such a relationship (Berkowitz et al., 1983; Kaminski and Papiernik, 1974;
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TOTAL AMOUNT AND PATTERN OF WEIGHT GAIN
117
Zuckerman et al., 1986~. If work or physical activity reduced the length
of gestation, total weight gain would also be reduced. Measurement of
the rate of gain could be used to adjust for differences in the length of
gestation.
Although many studies have been conducted on the effects of work
on pregnancy (i.e., birth weight, gestational duration, and complications of
labor and delivery), those few that provide data on weight gain (Naeye and
Peters, 1982; Tafari et al., 1980) provide little useful information about the
effect of work on weight gain.
CONCLUSIONS ANI) RECOMMENDATIONS
Since 1970, most reported average total pregnancy weight gains have
ranged between 10 and 15 kg (22 and 33 lb). The mean rate of gain during
the last half of gestation ranged from 0.45 to 0.52 kg (~1 lb) per week
The relatively low energy cost (~4.7 kcaVg) of tissue gain during preg-
nancy probably reflects the high concentration of water in the lean tissue
that is deposited. Hormonal adjustments that induce changes in the effi-
ciency of fuel use for tissue synthesis are possible, but actual measurements
of the energy cost for fat or lean tissue synthesis in pregnant women have
not been made.
Differences in the physiologic response to pregnancy may account for
much of the diversity in gains, but certain maternal factors, e.g., high
prepregnancy weight for height, short stature, black or Southeast Asian
background, very young age (<2 years after menarche), multiparity, un-
married status, and low income, are important predictors of a risk of low
weight gain. Maternal use of alcohol does not appear to affect weight gain
significantly. Furthermore, the limited data available do not show that work
outside the home or physical activity affects weight gain in U.S. women.
CLINICAL IMPLICATIONS
· Total weight gain during pregnancy varies widely among women
with similar ages, weights, heights, ethnic backgrounds, and socioeconomic
status. Gestation gains between the 15th and 85th percentiles range from
approximately 7 to 18 kg (16 to 40 lb). Therefore, recommended gains
should be used only as targets and for identifying individuals who should
be evaluated for insufficient or excessive rates of gain.
The observed rate of gain in the second and third trimesters ranges
from 0.3 to 0.7 kg (0.7 to 1.4 lb) per week. The average rate of gain
during the second trimester may be slightly higher than that during the
third trimester.
.
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118
NUTRITIONAL STATUS AND WEIGHT GAIN
· Within a population, the range of gestational weight gains is
wider among overweight women than among normal-weight or underweight
~ O _ ~ O
women.
· Although some investigators have reported different rates of gain
among teenagers and members of various minority groups, there is no
biologic evidence to justify different recommendations for these women.
· The risk of low weight gain (<6.8 kg, or 15 lb) is higher among
unmarried women, black and Hispanic women, cigarette smokers, and
women with low levels of education. These women should receive additional
nutritional counseling to ensure an adequate weight gain during pregnancy.
· No evidence was found to suggest that work outside the home
or regular physical activity increases the risk of low weight gains during
pregnancy.
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Representative terms from entire chapter:
white women
