neen blackwell alrutz · 2020. 9. 28. · in recent years, most research on maternal weight gain...
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A COMPARISON OF WEIGHT GAINS DURING
PREGNANCY OF NIC AND NON-WIC CLINIC SAMPLES
byNeen Blackwell Alrutz
Thesis submitted to the Graduate Faculty of the
Virginia Polytechnic Institute and State University
in partial fulfillment of the requirements
for the degree of
MASTER OF SCIENCEin
Human Nutrition
and;
Foods
APPROVED: . _
rL. Janette Taper, Cha rman
Jane Wentworth Anna Kanianthra
December, 1985
Blacksburg, Virginial
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koOß .
x Hä, A COMPARISON OF NEIGHT GAINS DURING
*27\ PREGNANCY OF NIC AND NON-NIC CLINIC SAMPLES
e byE
Neen Blackwell Alrutz
Committee Chairman: L. Janette TaperDepartment of Human Nutrition and Foods
(AssTRAcT>The purpose of this study was to find the difference,
if any, between the weight gain patterns during pregnancy of
women attending public health clinics in Northern Virginia
who were enrolled in the NIC program and women not enrolled
in the NIC program. Nomen on the NIC program during
pregnancy were identified from NIC files. The control group
was chosen from among women who were shown to be both
nutritionally at risk and eligible for NIC based on income,
but who were not receiving NIC benefits during pregnancy.
The sample consisted of M8 subjects in each group who
met certain other selection criteria. Nith the exception of
income, there was no statistically significant difference
when selected maternal and infant variables were compared.
There was no significant difference (p>.O5) between
total weight gain of the two groups, although the NIC
mothers gained slightly more during pregnancy than the non-
NIC mothers. A series of t-tests, performed between
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the means of the weekly weight gains, showed no significant
difference in the weekly weight gain of the two samples at
any week of pregnancy.
Both samples had increased weekly weight gains near the
end of pregnancy —— the mean of the non—WIC group was higher
and occurred slightly later than did that of the WIC
group. These higher means near the end of pregnancy for the
non—WIC group resulted in statistically significant
differences in the two groups when comparing the last part
of pregnancy and suggest that the non-WIC group is gaining a
larger amount of weight very late in pregnancy.
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ACKNOWLEDGEMENTS
I wish to thank the Virginia Department of Health, the
Arlington and Fairfax County Departments of Health and
Arlington and Fairfax Hospitals for permission to use
patient files for research purposes.
I received invaluable help from numerous WIC
nutritionists, nurses, clinic staff and medical records
staff who answered questions and searched for patient files.
I am grateful to the members of my committee: Mrs. Anna
Kanianthra, Northern Region Public Health Nutritionlst, who
conceived of the project and facilitated my research among
the WIC and public health clinics; Dr. Jane Wentworth for
her willingness to serve on short notice and her
contribution to improved writing style; and Dr. Janette
Taper for her always calm, helpful suggestions and prompt
availability over the seemingly long distance between
Blacksburg and Northern Virginia.
iv
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Table of Contents
Page
Acknowledgements.....................................ivTable of Contents.....................................vList of Tables...................................vi-viiIntroduction..........................................1
Background of the problem........................2Statement of the problem.........................3Hypothesis.......................................M
Review of Related Literature..........................5Factors influencing weight gain..................5Nutritional counselling and weight gain..........6Diet supplements and weight gain.................7Assessing weight gain............................8Weight gain patterns............................11WIC studies on weight gain......................15
Methodology..........................................16Subjects........................................16Data collection.................................19Data analysis...................................20WIC variables...................................23
Results and Discussion...............................2MMaternal variables..............................2MInfant variables................................2MSample characteristics..........................28
Race.........................................28Age.........................................•31Smoking habits...............................3MGestational age..............................35Body size at week 13.........................35Prepregnant weights..........................38Other variables...........................;..¤2Infant weight................................M5WIC characteristics..........................M5
Weeks on WIC..............................M5Nutritional counselling...................M8WIC eligibility...........................50
Control group variables........;.............52Weight gain patterns............................53
Weekly gains.................................53Gains by trimester...........................55Total weight gains...........................58
Limitations.....................................61Conclusions..........................................6MReferences........................................65-69Vita.................................................70
V
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List of Tables
Table No. Page
1 Reese Weight for Height Chart and Nomogram.......122 Proposed Weight Gain Patterns....................1M3 Data Collection Form.............................21M Frequency Distributions for Income of WIC
and Non-WIC Samples..............................255 Frequency Distributions for Length of
Gestation of WIC and Non-WIC Samples.............266 Frequency Distributions for Infant Birth-
weights for WIC and Non-WIC Samples..............277 Frequency Distributions for Race of
women in WIC and Non-WIC Samples.................298 Relation Between Race, Age, Maternal Weight
Gain and Infant Birthweight......................309 Frequency Distributions for Age of
Women in WIC and Non-WIC Samples.................3210 Relation Between Age, Maternal Weight Gain
and Infant Birthweight...........................3311 Influence of Nonsmoking, Moderate Smoking and
Heavy Smoking on Infant Birthweight andMaternal Weight Gain.............................36
12 Relation Between Length of Gestation Periodand Age, Maternal Weight Gain and InfantBirthweight......................................37
13 Estimated Size Based on Weight for Height atWeek 13 of Pregnancy for WIC and Non-WICSamples..........................................39
1H Influence of Mother's Estimated Body Size atWeek 13 to Means of Selected variables...........H0
15 Frequency Distributions for PrepregnantWeights for WIC and Non-WIC Samples..............H1
16 Frequency Distributions for Week of FirstPrenatal Clinic visit for WIC and Non-WICSamples..........................................M3
17 Frequency Dlstributions for Marital Status ofPregnant Women in WIC and Non-WIC Samples........MM
18 Frequency Distributions for Parity of Womenin WIC and Non-WIC Samples.......................M6
19 Frequency Distributions for Length of WICParticipation....................................M7
20 Relation of Length of WIC Participation toSelected variables..............................M9
21 Frequency Distributions for Risk FactorsDocumented Among WIC Subjects....................52
vi
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Table No. Page
22 Comparison of Weekly Means RepresentingPregnancy Weight Change from Week 8to Week M2 for WIC and Non—WIC Samples...........53
23 Comparison of Weight Gained for SelectedPeriods During Pregnancy of WIC andNon—WIC Samples..................................57
2M Cumulated Weight Gains for WIC andNon—wIC Samples..................................60
25 Means of Age, Birthweight and MaternalWeight Gain by Clinic............................63
vii
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INTRODUCTION
Since earliest times, the diets of pregnant women have
received special attention for cultural, social or medical
reasons. During the 18th and 19th centuries, increasedurbanization, poor diets and consequent malnutrition
resulted in rickets. The resultant poor bone formation
caused many women to have contracted pelves —— a major risk
to pregnant women if babies are large. In order to produce
smaller infants that could be delivered with relative ease,
doctors frequently recommended that pregnant women consume
low carbohydrate, low fat, diets in hope of maintaining low
weight gain (Worthington, 1977).
During the early 20th century, physicians placed limits
on the amount of weight a woman could gain during pregnancy
in hopes of avoiding preeclampsla and toxemia during
pregnancy (worthlngton, 1977). As early as the l9¤0's,
however, researchers began looking at optimal weight sain as
it related to successful pregnancy outcomes, specifically,
the highest number of healthy babies.
In recent years, most research on maternal weight gain
during pregnancy has been focused on the relationship of
weight gain to infant birthweight. Although many maternal
characteristlcs work together to predict pregnancy outcome,
and weight gain per se does not imply good nutritional
status, low maternal weight gain during pregnancy has been
1
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highly correlated with the likelihood of giving birth to a
low birthweight infant (less than 5.5 lbs.). Low
birthweight at term is associated, in turn, with high
perinatal mortality, poor growth and development and poor
intellectual development (Simpson, 1975).
Background of the Problem
The Special Supplemental Food Program for Women,
Infants and Children (WIC) was begun in 197M with the goal
of improving the health and nutrition of high risk pregnant
and lactating women and children up to the age of five. The
segment of the WIC program serving pregnant women addresses
directly several of the risk factors known to be associated
with low birthweight lnfants, particularly poor weight gain
of the mother over the course of pregnancy.
In 198¤, the General Accounting Office (GAO) prepared
an extensive review of WIC evaluations done throughout the
United States since WIC's inception in 1972. GAO reviewed
claims of WIC effectiveness in improving maternal nutrition
and found only inconclusive evidence that WIC could be
associated with improvements in maternal nutrition as
measured by a better diet, increased serum iron levels or
increased weight gain. In fact, very few of the WIC studies
have measured total weight gain or weight gain rate during
pregnancy. One reason for this is that data for these large
scale studies are usually garnered from birth certificates
and computerized WIC files —— neither of which contains
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extensive information on weight gain of the mothers over the
course of pregnancy.
Similarly, GAO found few “reliable" studies which
looked at WIG's effect on infant birthweight. Of these, GAO
concluded that there was “some support, but not conclusive
evidence“ that WIG participation increases infant
birthweight.
One way to clarify the impact of WIG on maternal weight
gain might be to focus on the weight gain of a WIG
population as compared to a non-WIG population. An
improvement in weight gain after initiation of WIG benefits
could signal higher total weight gain and, perhaps, higher
infant birthweight than might have been achieved without WIG
intervention. Similarly, a significant difference in weight
gain patterns, particularly during the last trimester of
pregnancy, between WIG and non~WIG women, could signify a
modulating effect of WIG benefits that might not be noticed
if either total maternal weight gain (measured at the end of
pregnancy) or birthweight were the only parameters measured.
Statement of the Problem
The present study was designed to see if pregnant women
who attend public health clinics for prenatal care and who
are enrolled in the WIG program, gain weight differently
than pregnant women who attend the same clinics, but who are
not receiving WIG benefits.
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Hypothesis
For the purpose of this study, the following null
hypothesis will be tested:
There is no difference in the means of the weekly
weight gains from weeks 13 to MO during pregnancy of women
who are enrolled in the WIC program and women attending the
same public health clinics who are not enrolled in the WIC
program.
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REVIEW OF RELATED LITERATUREFactors influencing weight gain
Many biological and sociodemographic factors work
together to determine the amount of weight a woman will gain
during pregnancy. Some factors which have been found to be
of more importance than others include weight prior to
pregnancy, race, and smoking habits.
Women who begin pregnancy 5% to 10% below ideal body
weight are thought to have an increased risk of delivering a
low birthweight infant, particularly if they have a small
weight gain during pregnancy (Johnson, 1983). Women who
begin pregnancy at less than 120 lbs. and who have a low
mean weight gain (less than 30 lbs.) are also at risk of
delivering a low birthweight infant (Eastman, 1968). Others
feel that women who begin pregnancy at less than 110 lbs.
and who galn less than 0.5 lbs. per week during the second
half of pregnancy more than double their chances of having a
low birthweight infant (van den Berg, 1981). Brown (1981)
found that among underweight women failing to gain more than
19.8 lbs., more than half of their infants weighed less than
5.5 lbs.
In the past, obese women have been encouraged to limit
weight gain or even lose weight during pregnancy (Gormican,
1980). Harrison (1980) found that 15% of moderately obese
women and 19% of massively obese women had inadequate weight
gains, while only M% of non—obese women had inadequate
5
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weight gains. Miller (1973) found obesity to be three times
more common in mothers of infants with severe fetal
malnutrition than among normal infants.
Kennedy (1982) found black mothers to have lowest
weight gains when compared to white and Hispanic mothers.
The reasons for this seem to be related less to race, per
se, than to the fact that race, like age, is correlated with
other biological and social variables which predispose a
woman to adverse pregnancy outcomes including poor weight
gain. Niswander (1969), on the other hand, found weight
gains to be essentially similar between Blacks and whites.
Pregnant women who smoke have decreased weight gain
over pregnancy (Kennedy, 1982), even when their calorie
intake is shown to be substantially increased over non-
smokers (Picone, Allen & Olsen, 1982; Picone, Allen &
Schramm, 1982).
Nutritional counselling and weight gain
There are few studies which try to assess directly the
influence of nutritional counselling on weight gain. One
such study (Orstead, 1985), compared two groups of pregnant
women. One group received intensive multiple counselling
sessions plus information on appropriate weight gain and
nutrient intake. The other group received a single group
counselling session. Orstead found that the women receiving
intensive counselling gained 5.5 lbs. more than the control
group and had fewer low birthweight infants (¤% vs. 13%).
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Many other factors are thought to influence weight gain
during pregnancy in varying degrees, including parity, age,
income, time of first clinic visit and supplemental feeding.
Diet supplements and weight gain
The major component of the WIC program is a
supplemental food package which provides about 800
kilocalories and MO grams of protein per day to pregnant
women through vouchers which they are given to buy milk,
cheese, juices, eggs and iron—fortified cereal (Endres,
1981).Researchers evaluating the impact of supplements to
pregnant women have differing conclusions concerning the
impact of such supplements on maternal weight gain. Most
studies have assessed the impact of food supplements on
infant birthweight rather than on maternal weight gain.
Rush (1981) matched women who received diet counselling
and food supplements with controls who were ineligible for
dietary services. He found no significant difference in
weight gain of mothers; yet the recipients' infants were
significantly heavier at birth than the contro1s' infants.
Adair (198H) examined effects of a maternalsupplemental feeding program on maternal weight among a
marginally malnourished population over the course of two
pregnancies. The anthropometry of women receiving
supplements did not seem to be affected, but infant
birthweights in the supplemented group were considered
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“favorable“ with low birthweight rates decreased. He
concluded, as did others (Lechtig, 1975; Mora, 1979), that
benefits to infants can be mediated via increases in the
maternal food supply without significant changes in maternal
body dimensions.
McDonald (1981) found a difference in the mean weight
gain of mothers who had received supplements, but the
difference was not statistically significant. Bhatnagar
(1983) studied third trimester supplementation among Indian
women. He found a significant difference between control
and supplemented groups in the mean weight gain from week 2M
to 36 of gestation.
Susser (1981) reviewed data in a New York study and
found that maternal weight gain was significantly improved
among women receiving supplemental food, but no similar
increment was seen in infant birthweight. Thus, in contrast
to Rush, Lechtig, Mora, Adair, and McDonald, the supplement
did affect maternal weight gain, but this weight gain was
not transposed into a birthweight increase.
In summary, there is evidence that increased maternal
intake in the form of supplements can affect maternal weight
gain in pregnancy and/or infant birthweight.
Assessing weight gain
Estimates on the optimal weight gain during pregnancy
are obtained by observing weight gain in normal pregnancies
of large samples of healthy women and by finding the weight
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9
associated with the lowest incidences of abnormalities.
Most authors calculate the weight gain as the weight of the
patient at her last prenatal visit or at delivery, less the
prepregnancy weight as stated by the patient. Others
(Gormican, 1980; Miller, 1973) have criticized the use ofprepregnant weight recalled by the patient at the time of
her first prenatal visit, pointing out that it is often
based on estimates. They have suggested using the maternal
weight as actually measured at the mother's first clinic
visit as a more realistic way to assess actual gain. The
disadvantage of this method is that it ignores any gain
(however small) that may have occurred in the first
trimester.
Wéight gain curves to measure ”normal“ weights and
assess adequate progress throughout pregnancy were first
proposed in the 19ü0's (Stander, 19MO) as part of a study to
learn more about toxemia. The early curve was based on
prepregnant weights of MO, 60 and 80 kgs. Suggested weight
gain was based on a percentage of these weights —~ about
2¤.1% gain from week 6 to week MO of pregnancy or an average
of 13.9 kg. (30.5 lbs.). This gain was considerably higher
than those found by most researchers at the time and well
above the weight gains being suggested by private physicians
during the l9¤0's and l950's.
Tompkins (1953) devised a weight gain curve based on
clinic patients which is still used today as a reference.
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He suggested total average cumulative weight gain during
pregnancy of 2M.6 lbs. This curve has been challenged
recently (Cogley, 1983) as inappropriate for the total
_population since it was based on a clinic population during
an era when physicians were recommending limited weight gain
(less than 20 lbs.).
Another method to monitor weight gain to assure
adequate gain during pregnancy was proposed by Gueri
(1982). In a variation of the standard weight for height
chart, he prepared a reference table derived from Health and
Nutrition Examination Survey (HANES) data for women aged 18
to 2M. The table is arranged by height by week of pregnancy
and is based on the theoretical assumption that a woman will
gain about 26.¤ lbs. or an average of 20% over her
prepregnant weight during the course of pregnancy. The
first 13 weeks of pregnancy assumes a 1.7% increment. The
remaining 18.3% is divided evenly over the next 27 weeks
(about 0.6 lbs. per week from weeks 13 to H0).
Gueri's system eliminates the need to know a
prepregnant weight, since if the week of pregnancy, the
height and present weight of the woman are known, the chart
will indicate a “normal“ weight. Someone weighing below
“normal“ weight for a particular week of gestation either
could have begun pregnancy underweight or could have not
gained sufficient weight during the course of pregnancy. In
either case, she would be at risk of not gaining sufficient
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ll
weight and she could be counselled to increase weight
gain. For an obese woman, the chart would not be useful
since she would presumably always have values above those on
the chart (for her weight and week of gestation) and a poor
rate of gain might not be observed.
Finally, Rosso (1985) devised a chart to monitor weight
gain and a nomogram to easily assess weight for height
adequacy at any point of gestation (see Table 1). This tool
does not overestimate the weight gain of obese gravidas and
can be used for women up to 1MO% above standard weight for
height. Neither does it underestimate the weight gain of
underweight women who, in some cases, may need a total
weight gain of 37.M lbs. or more to reach Rosso's proposed
goal of 1201 of standard weight for height by the end of
pregnancy.
Weight gain patterns
Pitkin (1983) noted that ”average" gains are not
necessarily equal to ”opt1mal“ gains for each person. Also,
he has suggested that the pattern of weight gain may be more
important than total gain in predictlng successful pregnancy
outcome. Nonetheless, he found the customary pattern to be
a 2.2 to M.M lb. gain in the first trimester and a 0.77 to
0.88 lb. per week gain during the remainder of pregnancy.
He found a linear gain from 10 to NO weeks, although the
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maximum rate occurred in the second trimester. He
considered inadequate a gain of 2.2 lbs. or less per month
(0.5 lbs. per week).
Numerous researchers have suggested appropriate weight
gains during pregnancy for normal pregnancies among well
nourished women. weight gains proposed by various authors
are listed in Table 2. The average weekly weight gain is
about 0.8 lbs. per week with a suggested range of 0.67 to
1.0 lbs. per week in the second trimester and a range of
0.67 to 1.2 lbs per week in the third trimester.
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14
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15
WIC studies on weight gain
Edozian (1979) found that pregnant women participating
in WIC from early pregnancy had longer gestational periods
and gained more weight when compared with women entering the
WIC program at a later stage of pregnancy. The greatest WIC
effect was seen in weight gain increases during the second
trimester. Mean birthweights of infants whose mothers
enrolled in the WIC program early were higher than among
other infants, although no direct relation between maternal
weight gain was claimed.
Metcoff (1982) compared weight of WIC and non—wIC women
at 19 weeks and 36 weeks. He found that WIC participants
weighed more at 36 weeks than the non—HIC women, but the
differences were not statistically significant.
Collins (1981) found no significant difference in the
maternal weight gain of WIC and non—WIC women or in the
birthweight of their infants. He concluded that since WIC
women were likely to be more at risk than other populations,
perhaps some benefit of WIC participation may have been
accrued by the WIC mothers.
In summary, there is little evidence in current WIC
studies that maternal weight gain is positively affected at
statistically significant levels by WIC participation.
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METHODOLOGY
The object of this study was to compare weight gain
patterns of two prenatal samples who attended public health
prenatal clinics in Northern Virginia. One group received
benefits of the NIC program during the pregnancy, the other
group received no NIC benefits during the pregnancy.
Subjects
Public health clinic records were obtained from four
clinic sites in Northern Virginia. The clinic patients who
were also receiving nutrition counselling and food vouchers
from the NIC program were ldentified by the NIC
nutritionists, by cross-referencing names on clinic rolls
with NIC mcnthly printouts, or by NIC files. These patients
became the NIC sample.
The comparison group of non—NIC clinic patients was
chosen from among patients who were found to be eligible for
NIC participation based on low income and certain
nutritional risk criteria, but who were not participating in
NIC during the pregnancy for which weight gain data were
recorded.
Since all patients attending public health clinics are
required to file income statements to determine ability to
pay, the income of all patients in the public health clinics
is known. The lower income levels for clinic patients are
16
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l7
identical to those used to determine WIG eligibility. Only
subjects whose low incomes would have qualified them for WIG
were chosen to be part of the comparison group.
The comparison subject was assumed to be at nutritional
risk if she met one of the following criteriaz
1) She had been referred to the WIG nutritionist by a
public health worker, she had been certified to be eligiblefor WIG, but she subsequently had been dropped from the WIG
rolls without recelving any WIG vouchers; or
2) She received WIG benefits during a recent or current
pregnancy, but during a previous pregnancy (within the last
five years) she did not receive WIG benefits. Records fromthe previous non—WIC pregnancy were used; or
3) She enrolled in WIG post-partum, but received no WIG
benefits during the pregnancy.
The samples were not randomly selected. Records were
chosen only if the following criteria were fulfilled:——age, race, height, parity and income of the mother were
known;
—~a fullsterm pregnancy occurred (defined as a gestation
period of from 38 to M2 weeks);——a single, live infant was born;——the infant birthweight was recorded;
——the patient first visited the clinic before week 18 ofpregnancy (in the final analysis only those visiting the
clinic on or before week 13 were included); and
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18
——information on weight gain was recorded at regular
intervals throughout pregnancy.
Approximately 500 prenatal records were screened
resulting in 1¤2 cases which contained the above
information. Of these, H6 were later discarded when it was
decided to analyze only records of patients who had begun
clinic visits no later than week 13 of the pregnancy. The
final analysis was done on H8 subjects in each group.
All initial information was gathered from four Virginia
Public Health Department clinic sites in the Northern Region
including Loudoun County, Fairfax County, Arlington County,
and Alexandria city. In the case of both Fairfax County and
Arlington County, additional information was reviewed for
each patient at Arlington Hospital and Fairfax Hospital,
since patients are seen by hospital clinic staff after the
28th week of pregnancy through delivery. In Arlington and
Alexandria, NIC files are sometimes kept separately from
clinic files, so that several sources were checked for each
patient.
No patient contact was made in any instance.
Permission to review public health records was made possible
under an agreement between Virginia Tech and the Virginia
Health Department. At Arlington Hospital permission to
review medical records was granted by the Institutional
Research/Review Committee. At Fairfax Hospital, permission
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19
was granted by the Assistant Administrator and the Director
of the Medical Records Department.
Data Collection
For each patient, information collected included clinic
name, marital status, race, age, income, height, smoking
habits during pregnancy, hematocrit values, prepregnant
weight (as stated by the patient), week of first clinic
visit, total number of prenatal visits, and actual weights
recorded at each clinic visit. Most patients visited the
clinic monthly until the third trimester when visits became
biweekly orweekly.For
infants, information collected included
birthweight, Apgar scores, sex and total weeks' gestation.
For WIC patients, information collected included the
number of weeks each woman was enrolled in WIC, the number
of nutrition counselling sessions attended and nutritional
risk factors which had originally qualified the mother for
WIC.
For control cases, the reason a patient was classified
as part of the comparison group was recorded.
Data collection was done slightly differently at each
clinic since each had different record—keeping systems and
different rules concerning researcher access to files. In
the Alexandria clinic, records were chosen by the medical
records department and pulled consecutively by the date of
clinic registration beginning in 1980. WIC files were then
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20
consulted to determine if the patient was on WIC at that
time. In Fairfax and Arlington, records were selected from
the list of clinic patients who had delivered babies since
1982. These lists were then divided into WIC and non—wIC
patients by comparison with WIC computer printouts (for the
pregnancies within the last two years) or old files.
In Loudoun, both WIC and public health clinic files are
kept together, so that the file itself contained all
relevant information.
Data were collected over a period of six months. See
Table 3 for data collection tool.
Data Analysis
The data were coded for analysis by the Statistical
Package for the Social Sciences—X <sPssx, 1985). Frequency
distributions, standard deviations, ranges and means were
found for the main descriptive variables. T—tests were
performed on continuous variables to discriminate between
the two groups. Chi square tests were done for certain
discrete variables. Pearson correlations were also
performed to ascertain relationships between selected pairs
of variables. Analsis of covariance was done for several
variables. All tests used significance levels of p<.05.
Based on the information collected, several additional
variables were computed.
Average weekly weight gain or loss was calculated based
on the recorded weights throughout pregnancy by dividing the
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21
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22
change in weight from visit to visit by the number of weeks'
between each visit (Cogley, 1983). A major assumption of
this method is that weight gain between observations had
been uniform during the interval (Stander, 19M0).
Cumulative gains were figured by adding average weekly
gains or losses from week 13 to the end of pregnancy.
Body size at week 13 was computed using the mother's
height and weight at week 13 of gestation. This factor was
calculated in order to compare the two samples in terms of
weight for height at the beginning of pregnancy to see if
one group began pregnancy substantially above or below
standard weight for height. Frequently, prepregnant weights
as recalled by the mother at the first clinic visit are
used, however, they cannot be clinically verified. In
addition, not all subjects had a prepregnant weight
recorded. A nomogram was used to eompute this factor
quickly (Rosso, 1985, see Table 1).
For purposes of this study the first trimester was
defined as from 1 to 13 weeks of pregnancy; the second
trimester from 1M to 26 weeks of pregnancy; and the third
trimester from 27 weeks to the end of pregnancy.
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23
WIC variables
Three additional variables were analyzed for the WIC
sample. Women were screened to ascertain the number of
weeks they had received benefits, the number of nutritional
counselling sessions they had attended and the specific risk
factors which had qualified them for WIC.
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RESULTS AND DISCUSSION
Maternal variables
There were no significant differences (p>.05) between
the two groups for the maternal variables of age, race,
marital status, parity, height, body size at week 13 of
pregnancy, prepregnant weight, smoking hablts during
pregnancy, week of first prenatal visit, and total visits
during pregnancy.
The only maternal variable which was found to differ
significantly between the two groups was income (Chi
Square=8.76, p=.o1>. In the WIC group, all but three cases
were in the most indigent category, while among the non—WIC
patients, only 70% were in the poorest category. Frequency
distributions for income are shown in Table N.
Infant variables
There were no significant differences between the two
groups in terms of gestational age, sex, or birthweight of
the infants. Frequency distributions for gestational age and e
birthweight are found in Tables 5 and 6.
In summary, except for income, there was no statistical
difference in any of the means of the maternal and infant
variables chosen to determine the similarity of the two
populations. Therefore, these two populations were assumed
to be similar.
24
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Table M. Frequency Distributions for Incomeof WIC and Non—wIC Samples
Income* WIC Percent Non*WIC Percent
A M5 93.8 3M 70.8
B 2 H.2 11 22.9
C 1 2.1 3 6.3
Chi Square=8.76, p-.01
*Public Health financial guidelines determining WIC eligibility changeperiodically. In 1985, to be eligible for WIC, gross annual income fora one—person family could not exceed $8,297 Der year.A——income range was $¤,981 — $5,¤75.B—~income range was $5,¤79 + $6,638.C——income range was $6,639 — $8,297.
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26
Table 5. Frequency Distributicns fcr Length cf Gestationcf NIC and Non—NIC Samples
Neeks NIC Percent Non—NIC Percent
38 5 10.44 7 144.6
39 7 144.6 144 29.2
440 22 445.8 15 31.3441 11 22.9 7 144.6442 3 6.3 5 10.44
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Table 6. Frequency Distributions for Infant· Birthweights fur WIC and N¤n—WIC Samples
WIC Non—WIC
lbs. Frequency Cumulative % lbs. Frequency Cumulative %
5.50 1 2.1 5.06 1 2.15.80 1 N.2 5.18 1 M.25.87 1 2.1 5.25 1 6.36.06 2 10.M 5.38 1 8.36.19 1 12.5 6.06 1 10.N6.25 1 1¤.6 6.13 1 12.56.38 1 16.7 6.31 1 1¤.66.50 1 18.8 6.N3 1 16.76.68 1 20.8 6.50 2 20.86.75 1 22.9 6.68 1 22.96.87 3 29.2 6.75 1 25.07.00 1 31.3 6.80 1 27.17.06 1 33.3 6.81 2 31.37.12 3 39.6 6.87 2 35.N7.13 1 M1.7 7.00 3 M1.77.19 1 N3.8 7.19 2 ¤5.87.25 1 N5.8 7.31 2 50.07.36 1 Ä7.9 7.37 1 52.17.38 2 52.1 7.¤3 1 5ü.27.¤3 1 5¤.2 7.56 1 56.37.NM 1 56.3 7.62 1 58.37.50 2 60.ü 7.68 2 62.57.56 1 62.5 7.75 1 6¤.67.81 1 6N.6 7.87 3 70.87.87 2 68.8 7.9¤ 1 72.98.06 3 75.0 8.09 1 75.08.12 2 79.2 8.19 3 81.38.18 1 81.3 8.38 1 83.38.19 1 83.3 8.56 1 85.M8.M3 1 85.N 8.62 1 87.58.50 2 89.6 8.68 1 89.68.62 1 91.7 8.87 1 91.78.69 1 93.8 9.13 1 93.88.9M 1 95.8 9.30 1 95.89.13 1 97.9 9.31 1 97.9
11.75 1 100.0 9.38 1 100.0
Mean = 7.¤6 lbs. Mean = 7.37 lbs.S.D. = 1.07 S.D. = 1.08
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_ Sample Characteristics
.‘i‘.§.§.The actual racial makeup of the various WIC clinics in
the Northern Region of Virginia varies greatly from clinic
to clinic. As a whole, the Northern Region is ¤1.5% white,
38.3% black, 12.3% Hispanic and 7.9% Asian (Ducey, 1985).
The racial composltion of this sample was M2.7% white, 39.6%
black, 12.5% Hispanic and 5.2% Asian. Thus, Blacks were
slightly over—represented and Asians under—represented.
Table 7 gives frequency distributions of each group by race.
Race is an important factor in discussing weight galn
since almost all recent studies have found that Blacks tend
to both gain less weight in pregnancy and have smaller
babies than other ethnic groups. The same held true for
this study. As Table 8 shows, Blacks galned the least
amount of weight (25.77 lbs.), and had the smallest infants
(7.08 lbs,). whltes gained the most weight overall (30.1
lbs.), but Hispanics had the largest infants (8.28 lbs.),
The mean infant blrthweight for all races was 7.M1
lbs. Results of an analysis of covariance using infant
weight as the dependent variable, total maternal weight gain
as a covariate and race as the independent variable show a
significant difference among the means of infant
birthweights based on race (p=.0O9). The Hispanic lnfants
were found to differ from both the black and white infants
at p<.05.
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Table 7. Frequency Distributicns for Race of Wcmenin WIC and Non—WIC Samples
WIC Percent Non~WIC Percent
White 20 M1.7 21 M3.8
Black 22 M5.8 16 33.3
Hispanic ¤ 8.3 8 16.7
Asian 2 M.2 3 6.3
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Table 8. Relation Between Race, Age,Maternal Weight Gain and Infant Birthweight
White Black Hispanic Asian(N=¤1) <N=38> (N=12> <N=5>
Age 21.8 21.6 25.2 26.2
Maternal weightgain (lbs.) 30.10 25.77 27.67 26.M5
Infant birthweight(lbs.) 7.*19 7.08 8.28 7.27
The relation between race and infant birthweight was statistically
significant (p=.009).
No statistical significance was found between race and maternal weightgain or age.
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Analysis of covariance using maternal weight gain as
the dependent variable, infant birthweight as covariate and
race as the independent variable found no relationship
between race and maternal weight gain, even though Whites
gained an average of 30.1 lbs. and Blacks only 25.77 lbs.
The reason for this lack of significance may be the fact
that the mean for all groups is 27.89 lbs., which falls
equidistant from the values of both Blacks and Whites.
lasAdolescents are thought to gain more weight, relative
to body size, than older women, and have smaller infants
(McCarthy, 1983). Mothers aged 19 and under accounted for
26% of the sample. Table 9 gives the frequency distribution
for each group by age. The mean birthweight of their
infants was 6.98 lbs. while the mean birthweight of women
age 20 and over was 7.57 lbs.
An analysis of covariance using infant birthweight as
the main dependent variable, maternal weight gain as a
covariate, and age (less than 20 years, or 20 years and
older) as the independent variable showed age to be related
significantly (p=.016) to infant birthweight, in that the
younger the mother, the lighter the infant at birth.
In terms of weight gain, the younger group gained
slightly more than the older group (28.0ß lbs. to 27.8M
lbs.) but not at a statistically significant level. See
Table 10.
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Table 9. Frequency Distributions for Age cf womenin WIC and Non-WIC Samples
Non·—WIC
Age Frequency Percent. Age Frequency Percent(yrs.) „__.__ (yrs.)
15 1 2.1 16 1 2.1
16 N 8.3 17 5 10.N
18 1 2.1 18 3 6.3
19 6 12.5 19 M 8.3
20 7 1N.6 20 6 12.5
21 6 12.5 21 5 10.M
22 3 6.3 22 2 M.2
23 5 10.N 23 N 8.3
2M 2 N.2 2N 5 10.M
25 5 10.N 25 1 2.126 2 ü.2 26 3 6.3
27 1 2.1 27 2 N.2
28 2 *4.2 29 3 6.329 1 2.1 30 2 N.2
32 1 2.1 36 2 *4.23M 1 2.1
N = *48 N = *48Mean = 22.1 Mean = 22.6S.D. = *4.06 S.D. = *4.72
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Table 10. Relation Between Age, Maternalweight Gain and Infant Birthweight
age 19 or under age 20 or over Probablllty‘ (N=25) (N=71)
Maternal weight‘ gain (lbs.) 28.0M 27.8M not significant
Infant birthweight(lbs.) 6.98 7.57 p=.O16
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Smoking habits
Smoking gravidas are well known to have smaller infants
than nonésmokers. This proved true in this study as infants
of women smoking more than one—half pack per day had a mean
birthwelght of 6.93 lbs., while the infants of non~smokers 1
had a mean weight of 7.67 lbs.
An analysis of covariance was performed using infant
weight as the dependent variable, total maternal weight gain
as a covariate and smoking as the independent variable.
Smokers were divided into two groups, moderate smokers ——
those smoking one~half pack or less per day —— and heavy
smokers —+ those smoking more than one—half pack per day.
The relationship between smoking and birthweight was
statistically significant (p=.023).
Researchers (Kennedy, 1982; Picone, 1982; Davies, 1976)
have found that non—smokers gained more weight than
smokers. In this study, the non—smokers gained slightly
more than the moderate smokers, but slightly less than the
heavy smokers.I
An analysis of covariance was done using total weight
gain as the dependent variable, with infant birthweight as
the covariate and smoking as the independent variable.
There was no significant relationship (p>.O5) found to exist
between maternal weight gain and smoking.
The fact that the weight gain among the heaviest
smokers was higher than among non—smokers, while the mean
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weights of their infants were smaller than that of infants
of non—smokers, suggests, perhaps, some compensatory attempt
by the body to overcome the infant's reduced access to
nutrients and oxygen due to smoking by the mother. Table 11
describes the relation between amount smoked, maternal ·
weight gain and infant birthweight.
Gestational age
The number of weeks a woman is pregnant before delivery
is known to have a major influence on both the total amount
of weight gained and the blrthweight of her infant. Nomen
who delivered infants at week 38 gained an average of 30.15
lbs. and had infants weighing an average of 6.73 lbs. Nomen
carrying infants until week M2 gained an average of 3M lbs.
and had infants weighing 8.8 lbs.
Analysis of covariance found a statistically »significant relation between the length of gestation and
infant birthweight (p·.O01) and between the length of
gestation and maternal weight gain (p=.O26). See Table 12.
Body size at week 13
Nhile more NIC women (33.3$) were 120% or more aboveideal body weight at the beginning of pregnancy when
compared to non—NIC women (18.8%), no significant
differences (p>.05) were found between the groups based on
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Table 11. Influence of Nonsmoking, Moderate Smoking andHeavy Smoking on Infant Birthweight and Maternal weight Gain
Infant Birthweight Maternal Weight Gain(lbs.) (lbs.)
Non-smokers (N=58) 7.67 28.25
Moderate smokers (N=21) 7.0M 27.78
Heavy smokers (N=8) 6.93 29.00
Mean for entire sample 7.N5 28.21(N = 87)
The relation between smoking and birthweight was significant (p=.023).No statistical significance was found between maternal weight gain andsmoking.
Moderate smokers — one—half pack or less per day.Heavy smokers - more than one—half pack per day.
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Table 12. Relation Between Length of Gestation PeriodAge; Maternal weight Gain and Infant Birthweight
Week of Delivery
38 39 H0 M1 M2N=12 N=21 N=37 N=18 N=8
Age (yrs.) 22.5 21.3 22.6 22.7 23.0
Maternal weightgain (lbs.) 30.15 25.85 2¤.76 32.50 3¤.63
Infant birthweight(lbs.) 6.73 7.28 7.l10 7.62 8.81
N = 96
The relation between infant birthweight and week of gestation wasstatistically significant (p=.001).
The relation between week of gestation and maternal weight gain wasstatistically significant (D·.026).
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overall relative weights of both groups. Frequency
distributions comparing the relative size of both groups at
week 13 of pregnancy are found in Table 13.
Analysis of covariance shows no significant
relationship between the body size de week 13 of pregnancy
to either weight gain or infant weight. However, as Table
1H shows, the most underweight women —~ those less than 80%
of ideal body weight ~— gained the greatest amount of weight
and, along with women weighing from 80% to 89.9% of ideal
body weight, had the smallest children. These findings
confirm those of Rosso (1985). Other observations include
the fact that the most overweight women had the largest
children.
Prepregnant weights
A review of the prepregnant weights as stated by the
mothers at the first clinic visit, showed that the non—wIC
group began pregnancy at lower weights than did the WIC
group. Among the non—WIC mothers, 32.M% began pregnancy at
110 lbs. or less, while only 17.1% of the WIC mothers had
weights at that level. Table 15 gives frequency
distributions for prepregnant weights of women in the WIC
and the non-WIC groups.
In terms of overweight women, 18.9% of the non—WIC
mothers stated that they weighed over 150 lbs. at the start
of pregnancy; 20.2% of the WIC women admitted to beginning
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Table 13. Estimated Size Based on Weight for Height at Week 13‘ of Pregnancy for WIC and Non—WIC Samples B
Percentideal body weight WIC Percent Non-WIC Percent
< 80% 2 N.2 2 N.2
80 to 89.9% 5 10.ü 7 1M.690 to 99.9% 7 1N.6 10 20.8100 to 120% 18 37.5 20 N1.7
> 120% 16 33.3 9 18.8
Rosso P., (1985) Am. J. Clin. Nutr. H1, 6¤¤—652
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41
Table 15. Frequency Distributions for Prepregnant weights‘ Among Women for WIC and N0n—WIC Samples
Cumulative Cumulativeweight WIC percent Weight N0n—WIC percent
90 1 2.9 89 1 2.7100 1 5.7 94 1 5.4105 2 11.4 98 1 8.1110 2 17.1 99 1 10.8113 1 20.0 105 2 16.2114 1 22.9 107 1 18.9115 1 25.7 109 1 21.6117 1 28.6 110 4 32.4118 1 31.4 115 5 45.9120 1 34.3 119 1 48.6125 2 40.0 120 1 51.4128 3 48.6 123 1 54.1129 1 51.4 125 2 59.5130 3 60.0 126 1 62.2135 2 65.7 130 1 64.9141 1 71.4 135 4 75.7142 1 74.3 137 1 78.4145 2 80.0 145 1 81.1150 1 82.9 150 4 91.9165 2 88.6 155 1 94.6170 1 91.4 163 1 97.3185 1 94.3 165 1 100.0195 1 97.1235 1 100.0
N = 35 N = 38Median = 129 Median = 120Mean = 134 Mean = 124
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42
pregnancy at weights above 150 lbs. About one—fourth of the
women had no prepregnant weights listed in their files.
Other variables
Other variables reviewed included total clinic visits,
week of first clinic visit, marital status and parity. The
WIC group recorded almost one more clinic visit per person
than the non—WIC group (12.75 compared to ll.87), although
it was not found to be statistically significant (p>.05) One
possible reason for this finding was that WIC visits were
counted as a prenatal visit since weights were taken and
counselling occurred.
No differences were found between the two groups as far
as week of the first prenatal visit. Data were coded only
from week 8 so that, in fact, some women could have begun
attending clinic earlier. Table 16 gives frequency
distributions for week of first prenatal visits.
In each group, the marital status was unknown for about
one—third of the population. Of those known, among WIC
mothers, M35 was married, while 53% of the non—WIC mothers
was married. While these figures were not found to be
statistically significant (p>.05), it may help explain why
the NIC group was considerably poorer than the non—WIC
group. Frequency distributions for marital status are found
in Table 17.
This pregnancy represented the first child for ¤3.8% of
the WIC mothers, while 62.5 % of the comparison group had no
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Table 16. Frequency Distributions for week cfFirst Prenatal Clinic Visit. for WIC and Non—WIC Samples
Week WIC Percent N¤n—·WIC Percent(N=118) (N=1·|8)
8 3 6.3 12 25.09 10 20.8 9 18.8
10 12 25.0 3 6.311 11 22.9 8 16.712 5 10.11 5 10.1113 7 111.6 11 22.9
Mean == week 10.5 Mean = week 10.11
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Table 17. Frequency Distributions for Marital Status of‘ Women in WIC and Non—WIC Samples
WIC Non—WIC(N==!|8) (N=1|8)
Married 1H 19
Single/Divorced 18 16
Unknown 16 13
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other children. While differences in these groups were not
found to be statlstically significant (p>.05) parity could
be a factor in weight gain, particularly in the third
trimester, since primiparous women are thought to gain
slightly more weight than multiparas (Brenner, 1972,
Worthington, 1977). Table 18 gives frequency distributions
for parity of the two groups.
Infant weight
There was no statistical difference (p>.05) in the
means of the birthweights of the two groups. The mean
birthweight among WIC infants was 7.¤6 lbs. and the mean
among the non—WIC infants was 7.37 lbs. However, no infants
in the WIC group weighed less than 5.5 lbs., while four
infants in the non—WIC group weighed less than 5.5 lbs.
Among non-WIC infants, 35.¤$ weighed less than 7 lbs., while
only 29.2 of the WIC infants weighed less than 7 lbs. Table
6 gives frequency distributions for infant birthweight.
WIC characteristics
Weeks on WIC
The mean number of weeks on WIC was 20.9. By week 20
of pregnancy 6¤.7% of women had actually enrolled in the
program. See Table 19 for frequency distributions for the
number of weeks on WIC. In all clinics except Arlington,
WIC participants registering before mid-pregnancy were
almost twice as numerous as those registering after week 20.
Although neither total weight gained nor lnfant
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Table 18 Frequency Distributions for Parity of Women‘ in WIC and Non-WIC Samples
Number WIC Percent Non-NIC Percentof Children
O 21 *13.8 30 62 .51 15 31.3 1M 29.22 8 16.7 2 M.23 2 N.2 2 N.2L! ...;.6 .6... ....6 6...
5 2
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Table 19. Frequency Distributions for Length of NIC Participation
Number of weeks on WIC Frequency Cumulative %
33 1 2.1
31 1 4.2
30 3 10.5
29 6 20.928 M 29.2
26 1 31.3
25 3 37.62N 3 N3.9
22 N 52.2
21 5 62.6
20 1 6u.719 1 66.8 y_18 1 68.916 1 71.0
n
15 2 75.2 21N 3 81.5
13 2 85.712 1 87.8
11 1 89.910 1 92.0
7 2 96.26 1 98.35 1 100.0
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48
birthweight was found to be related statistically <p>.o6> to
the amount of weeks a subject was enrolled in NIC, several
findings were of interest. Of the mothers who gained more
than 25 lbs. throughout pregnancy, 65% began receiving NIC
benefits before week 20 of pregnancy. The majority of
infants weighing more than 7 lbs. (67%) were born to mothers
who began the NIC program before mid-pregnancy. Of the
infants weighing less than 7 lbs. at birth, more than half
had mothers who began receiving NIC benefits after mid-
pregnancy. See Table 20 for details.
An analysis of covariance was done using total weight
gain as the dependent variable, infant weight as the
covariate and weeks on NIC (20 or more; less than 20) as the
independent variable. Nhile the differences between the
groups were not statistically significant (p>.05), the mean
weight gain for women on NIC 20 weeks or more was 29.7 lbs.,
while those on NIC less than 20 weeks gained an average of
25.73, a difference of almost M lbs.
Those on NIC for fewer weeks than 20 had infants
weighing an average 7.7 lbs., slightly more than the mean of
7.2 lbs. for those on NIC for longer period; however,
analysis of covariance showed no significant relation
(p>.05) between the weeks on NIC and the infant birthweight.
Nutritional counselling
NIC women.received nutritional counselling from a NIC
nutritionist from one to five times during pregnancy, with a
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Table 20. Relation of Length of WIC of Participationto Selected variables
Subject on WIC Subject on WIC20 weeks or more less than 20 weeks
(N=31) (N=17)
No. of infants weighingover 7 lbs. 23 11
No. of infants weighingless than 7 lbs. 8 6
N6, gf mothers gainingover 25 lbs. 21 10
No. of mothers gainingless than 25 lbs. 10 7
Mean infant birthweight(lbs.) 7.2 7.7
Mean maternal weight gain
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mean of 1.5 counselling sessions. An analysis of covariance
using nutrition counselling showed no statistically
significant relationship (p>.O5) of counselling to
birthweight.
An analysis of covariance examining the relationship
between total weight gain and nutritional counselling found
p=.057 which, while not significant under the parameters of
this analysis, might point the way to other research.
However, since no other independent variables were taken
into consideration and the numbers were small (N=M8), no
conclusions can be made about the relation of nutrition
counselling to weight gain.
WIC eligibility
The vast majority of women (87%) were found to be
eligible for WIC because of inadequate diets. Thiß finding
was made based on diet histories and/or diet recalls done on
one or more occasions by a WIC nutritionist. The next most
prevalent reasons that women were certified eligible were
anemia (based on hematocrit values of less than 3M%),
obesity and/or excessive weight gain of 7 lbs. or more per
month, and adolescent pregnancy.
Other reasons women are eligible for WIC include:
frequent conception with less than 2M months between
pregnancies; low weight gain —— 2.2 lbs. or less per month
during the second and third trimesters, or being 10% or more
under ideal weight for height; a high risk pregnancy based
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Table 21. Frequency Distributions for Risk FactorsDocumented Among WIC Subjects*
Risk Number of Women
Inadequate diet N2Anemia 1MObesity 8Age 7Frequent conception N
Low weight gain MIncreased risk pregnancy 2Smoking 1Food faddism 1Fear of regression 1Abortion 0
*Some women had several risk factors
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on two or more previous pregnancies having resulted in a low
birthweight infant, stillbirth, or congenital anomaly;
excessive smoking -— over one pack per day; food faddism,
including dietary faddism, pica or food allergy; fear of
regression, or lack of confidence in ability to maintain~
weight gain; and spontaneous abortion or two therapeutic
abortions within the last 2M months. Table 21 shows the
frequencies of various risk categories am¤¤8 the NIC sample.
Control group variables
Post—partum referrals accounted for 39.61 of the
comparison group; 351 were referred to NIC during pregnancy
but never received benefits; and 251 were found to be
eligible for NIC during a recent pregnancy, but the data on
maternal weight gain and infant weight were taken from a
prior pregnancy when the woman was not on NIC.
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Weight Gain Patterns
Weekly gains
A weekly gain or loss for each individual was figured
based on actual measurements in clinic throughout pregnancy.
Then, the mean of each week°s values was figured to give
each group, WIC and non—WIC, an overall value for each
weekly interval. The weekly gains of each group were not
statistically different (p>.05) based on the results of t-
tests done consecutively from week 8 to week M2.
The weekly gains in the second trimester (week 1M to
26) were slightly larger than were observed by researchers
described in Table 2. A gain of about 0.8 lbs./week during
the second trimester has been found in most studies. In
this study, however, after week 16, there are few values
that are less than 1.0 lbs./week“—notably only 0.9 lbs.
recorded for the control group in weeks 21, 22 and 23. Only
Humphreys (195M) found gains averaging as high as these in
the second trimester.
The mean gains found in week 39 for the WIC group and
week H0 for the comparison group are of special interest
because when cumulative gain is figured, they cause
unexpected and otherwise unexplained increases in total
weight gain for the comparison group in the final weeks of
pregnancy. Description of the means by week is found in
Table 22.
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Table 22. Comparison of Weekly Means Representing Pregnancyweight Change from week 8 to Week M2
for WIC and Non-WIC Samples
Week WIC Non-wICgestation N lbs. N lbs.
8 0 0.0 3 0.MM39 3 0.773 11 0.M9510 1M -0.115 20 -0.01911 2M 0.177 25 0.2M812 36 0.673 31 0.M3113 M8 0.591 M8 0.3191M M8 0.502 M8 0.50515 M8 0.718 M8 0.87016 M8 0.880 M8 0.91217 M8 0.930 M8 1.07318 M8 1.1M7 M8 1.09M19 M8 1.308 M8 1.05120 M8 1.130 M8 1.0M721 M8 1.1M5 M8 0.97022 M8 1.081 M8 0.95523 M8 1.0M2 M8 0.95M2M M8 1.0M6 M8 1.20825 M8 1.22M M8 1.10M26 M8 1.099 M8 1.17627 M8 1.33 M8 1.30828 M8 1.136 M8 1.06329 M8 1.095 M8 0.89930 M8 1.089 M8 0.89031 M8 1.227 M8 1.0M732 M8 1.029 M8 1.M0333 M8 .939 M8 1.2133M M8 .995 M8 1.20535 M8 1.161 M8 1.11736 M8 1.127 M8 0.95937 M8 1.02M M8 1.06738 M8 0.719 M8 0.67239 37 1.525 32 1.188M0 2M 1.197 18 1.69MM1 7 0.1M3 10 0.925M2 0 0.0 3 1.0
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Gains by trimester
0ne of the problems of figuring gains by trimester and
comparing them with results of other studies is that very
few studies explain which weeks are included in a
trimester. Theoretically, if gestation is H0 weeks long, a
trimester period is composed of 13.3 weeks or 13 weeks and
2.3 days. For this study, however, use of any measure
smaller than week would have been impossible given the type
of the data available.
Although some patients began attending clinic very
early in gestation, information was coded beginning with
week 8. Based on increaslng numbers of cases each week, the
mean gain during the first trimester was 2.02 lbs. for the
non-WIC group and 2.09 lbs. for the WIC group. Throughout
that entire period, the individual data have many negative
values, representing losses from week to week. These gains
are smaller than those proposed by the majority of the
researchers reviewed, many of whom suggest a gain in the
first trimester of about 3 lbs.
In the second trimester, the WIC group had a mean
weight gain of 12.2¤ lbs.; the non—WIC group a galn of 11.83
lbs. The values for second trimester gain were very close
to those proposed by others (Tompkins, 1953; Beal, 195M;
Cogley, 1983). WIC participants gained more weight than
non—participants for every period studied that began at mid-
pregnancy (week 20) through week 38.
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The situation changes when third trimester gains are
considered. The non—wIC group gained more weight than the
WIC group for every period studied that began in week 27 or
later. Comparative gains for selected periods are displayed
in Table 23.
The non—wIC group seems to have gained at an increased
rate in the last weeks of pregnancy. The explanation for
this increased rate could be related to the fact that more
of the non—WIC subjects began pregnancy underweight, while
more of the WIC subjects began pregnancy overweight. The
comparison group, therefore, may have had more compensatory
weight gain to achieve. On the other hand, the main
components of weight gain in the later weeks are known to be
increases in infant growth stores rather than maternal
stores which occur earlier in pregnancy.
Another explanation might be found in the kinds of
foods eaten by the respective groups. After receiving WIC
vouchers for at least four months, WIC gravidas could have
been sensitized to appropriate eating patterns. The non-WIC
group, without benefit of specific eating guidelines, could
have been eating inappropriate and high calorie foods.
Edema, or water retention in the last weeks of
pregnancy, could be accounting for increased gains late in
pregnancy in both groups. Gentz (198M) estimates that most
women (80%) will develop either temporary or permanent edema
during pregnancy and that at least ¤O% of all women report
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Table 23. Comparison of weight Gained for Selected PeriodsDuring Pregnancy of WIC and Non—WIC Samples
NIC Non—wICWeeks N lbs. N lbs. T Probability
1M to 26 M8 12.2M M8 11.83 · N.S.
21 to 32 M8 12.60 M8 11.69 * N.S.
21 to 35 M8 15.50 M8 15.M0 — N.S.21 to 38 M8 18.83 M8 18.57 * N.S.
21 to 39 37 19.29 32 20.81 — N.S.
21 to MO 2M 20.02 18 2M.93 2.29 p=.02
27 to 39 37 12.52 32 1M.31 — N.S.
32 to 39 37 6.92 32 8.80 2.01 p=.0M
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generalized swelling by the 38th week of pregnancy. In
fact, mild edema has been found to be associated with higher
birthweight and a lower incidence of premature delivery.
Thus, the total weight gain calculated at the very end of
pregnancy may be a less than accurate appraisal of actual
fetal growth and maternal stores.
Total weight gains
"Total" weight gain was calculated by two methods in
in this study. Weight gain for each individual was
calculated from information given in the medical record by
subtracting the weight given at the first clinic visit
regardless of week (8 through 13) from the weight at the
last clinic visit regardless of week (38 through M2) prior
to delivery. A disadvantage of using this method is that it
assumes all pregnancies are the same length and gives no
information about the length of gestation or rate of gain.
Nevertheless, this figure was entered into the original
data and was used as a dependent variable when a "total“
weight gain was needed to compare with the various
independent variables of race, age, smoking, income, and
weeks on WIC.
A t—test was used to compare the means of the total
weight gained by the women in the WIC group and the women in
the non—WIC group. No significant difference (p>.05) was
found between the two groups. Women in the WIC group gained
28.3 lbs. over the course of pregnancy while women in the
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non—WIC grouped gained 27.¤9 lbs. This finding agrees with
results of others (Edozian, 1979; Metcoff, 1982).
“Total" weight gain was also calculated by cumulatively
adding the weekly means beginning with week 13. This method
has the disadvantage of ignoring early gains; however, it
does give an indication of where changes in a rate of gain
might occur. No statistically significant difference was
found between the cumulated means at any week. As was true
for the other calculations involving periods of gain, from
week 13 through week 38, the WIC group had marginally higher
cumulative gains. Beginning after week 39, however, the
comparison group had increased gains. See Table 2M.
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60 ~
Table 2M. Cumulated Weight Gaius for WIC aud Nou—WIC Samplesfor Various Peviods
WIC N0u—wIC Probabilityweeks N lbs. N lbs.
13 to 38 M8 26.0 M8 25.M N.S.
13 to 39 37 26.7 32 26.0 N.S.
13 to NO 2M 27.5 18 28.7 N.S.
13 to N1 7 29.3 10 33.2 N.S.
13 to N2 0 *— 3 36.7 N.S.
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61
Limitations
The limitations of the study include the fact that the
samples were not randomly selected and the sample size was
small. As outlined in the earlier section on methodology,
subjects were included in the study based on the presence of
certain information in their medical files. While data were
collected on 1¤2 subjects, 96 subjects were chosen for the
final analysis based solely on whether or not prenatal
clinic visits were begun by week 13 of pregnancy.
This choice automatically excluded from the sample
women with little or no prenatal care —— those who were most
likely to have the greatest complications throughout
pregnancy, including low weight gain and low birthweight
infants. Thus, the sample is not representative of the
total actual clinic population in Northern Virginia, only of q
those women who begin pregnancy checkups relatively early.
Finally, the results of four clinics were pooled.
Although the racial composition of the entire group mirrors
the general racial/ethnic makeup of the WIC population in
Northern Virginia, each clinic varies widely in the
predominance of one racial group or another. At the same
time, the Loudoun clinic has vastly fewer numbers of of
patients per month than the other clinics which are about
equal in numbers of patients seen per month. In the study,
however, the number of subjects from the Loudoun clinic is
GDDPOXIMBCSIY equal to the number of subjects from each of
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the other clinics, thus disproportionately representing the
chavacteristics of Loudoun clients. Table 25 gives the
means for age, birthweight and total maternal weight gain by
clinic.
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Table 25. Means of Age, Birthweight and MaternalWeight Gain by Clinic
Age Birthweight Maternal Gain(yrs.) (lbs.) (lbs.)
Loudoun (N=28) 20.H 7.57 28.6M
Fairfax (N=21) 23.N 7.3¤ 30.06
Arlington (N=22) 25.1 7.53 27.03
Alexandria (N=25) 21.0 7.20 26.01
Means for entire sample 22.6 7.¤1 27.89
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CONCLUSIONS
The null hypothesis of this study was that there is no
difference in the means of the weekly weight gains from week
13 to MO during pregnancy of women who are enrolled in the
WIC program and women attending the same public health
clinics who are not enrolled in the WIC program. The null
hypothesis could not be rejected, since there was no
difference in the means of weekly weight gains at any week
during pregnancy.
As Thomson (1957) has observed, it is difficult to
analyze statistically weight changes in pregnancy. For
accurate results, one needs to weigh all pregnant women at
frequent intervals from conception to birth —— an obvious
lmpossibility.
The lack of difference in weekly means between the two
groups in this study indicates either that the two groups
were too similar to be differentiated by the method used or,
that the methods used in finding the average weekly means
and then averaging those means to come up with one figure
per week for each group, projected too many distortions into
the data to make it meaningful.
Findings of interest are the relatively high means
found late in pregnancy which, when cumulated, show the non—
WIC group to be gaining disproportionately large amounts of
weight in the final weeks of pregnancy.
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65
The more interesting and, perhaps, more relevant
results center around the relations of certain maternal
variables and WIC effects to maternal weight gain and infant
weight among the selected women in each of the groups.
The finding that teenagers and women beginning
pregnancy most underweight, gained the most weight, yet had
the smallest infants confirms current WIC emphasis on
identification and counselling of both young and underweight
women.
The current knowledge concerning the harm to infants of
smoking was confirmed in light of the fact that non-smokers
had heavier infants than smokers. Maternal weight gain,
however, was higher for one category of smokers, a finding
that differs from many research studies on smoking.
Finally, effects of the length of WIC participation
were broadly measured. Women spending longer on WIC gained
more weight than those women on WIC for shorter periods.
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