Gestational Weight Gain and Postpartum Diabetes

Association between Gestational Weight Gain and
Postpartum Diabetes: Evidence from a Community Based
Large Cohort Study
Abdullah Al Mamun1*, Munim Mannan1, Michael J. O’Callaghan2,3, Gail M. Williams1, Jake M. Najman1,
Leonie K. Callaway3,4
1 School of Population Health, The University of Queensland, Brisbane, Australia, 2 School of Medicine, The University of Queensland, Brisbane, Australia, 3 Royal Brisbane
and Women’s Hospital, Brisbane, Australia, 4 Mater Children’s Hospital, and The University of Queensland, Brisbane, Australia
Abstract
We have investigated the prospective association between excess gestational weight gain (GWG) and development of
diabetes by 21 years post-partum using a community-based large prospective cohort study in Brisbane, Australia. There
were 3386 mothers for whom complete data were available on GWG, pre-pregnancy BMI and self-reported diabetes 21
years post-partum. We used The Institute of Medicine (IOM) definition to categorize GWG as inadequate, adequate and
excessive. We found 839 (25.78%) mothers gained inadequate weight, 1,353 (39.96%) had adequate weight gain and 1,194
(35.26%) had gained excessive weight during pregnancy. At 21 years post-partum, 8.40% of mothers self-reported a
diagnosis of diabetes made by their doctor. In the age adjusted model, we found mothers who gained excess weight during
pregnancy were 1.47(1.11,1.94) times more likely to experience diabetes at 21 years post-partum compared to the mothers
who gained adequate weight. This association was not explained by the potential confounders including maternal age,
parity, education, race, smoking, TV watching and exercise. However, this association was mediated by the current BMI.
There was no association for the women who had normal BMI before pregnancy and gained excess weight during
pregnancy. The findings of this study suggest that women who gain excess weight during pregnancy are at greater risk of
being diagnosed with diabetes in later life. This relationship is likely mediated through the pathway of post-partum weightretention and obesity. This study adds evidence to the argument that excessive GWG during pregnancy for overweight
mothers has long term maternal health implications.
Citation: Al Mamun A, Mannan M, O’Callaghan MJ, Williams GM, Najman JM, et al. (2013) Association between Gestational Weight Gain and Postpartum Diabetes:
Evidence from a Community Based Large Cohort Study. PLoS ONE 8(12): e75679. doi:10.1371/journal.pone.0075679
Editor: Kaberi Dasgupta, McGill University, Canada
Received April 15, 2012; Accepted August 20, 2013; Published December 11, 2013
Copyright: 2013 Al Mamun et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits
unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Funding: The core study was funded by the National Health and Medical Research Council (NHMRC) of Australia. AAM is supported by a Career Development
Fellowship from the NHMRC (ID 519756). For the work in this paper AAM has a grant from the National Heart Foundation of Australia (ID G07B3135). The funders
had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. The views expressed in the paper are those of the
authors and not necessarily those of any funding body and no funding body influenced the way in which the data were analysed and presented.
Competing Interests: The authors have declared that no competing interests exist.
* E-mail: mamun@sph.uq.edu.au
Introduction
While weight gain has long been associated with the development of diabetes relatively little has been written about the
possibility that gestational weight gain (GWG) may be an
independent predictor of diabetes onset in later life. The institute
of Medicine (IOM) [1] defined GWG as inadequate, adequate and
excessive, with appropriate GWG dependent on pre-pregnancy
body mass index (BMI). This has been a commonly used indicator
to predict post partum weight retention (PPWR) in the short and
long- term [2–4]. A recent meta analysis of observational cohort
studies found that women who had excess GWG continued to gain
more weight throughout life compared to women with women
with adequate GWG. On average those who gained excess GWG
had gained 4.72 kg (95%CI:2.94, 6.50) over more than 15 years
post-partum compared to women with adequate GWG. Those
with inadequate GWG demonstrated lower average weight gain in
the short and medium term [5]. An observational cohort study has
also reported that women with excess GWG were at greater risk of
becoming overweight and obese two decades later, independent of
potential confounders and mediators [6]. Weight gain, overweight
and obesity during midlife, particularly among women, are strong
independent predictors of cardiovascular disease, metabolic
syndrome, diabetes and early mortality [7–9]. However, it is
unknown whether GWG independently contributes to the burden
of diabetes.
The association between GWG and diabetes later life is
biologically plausible because of the link between GWG, PPWR
and the development of obesity [1]. Substantial weight gain during
childbearing [10] has been associated with increased visceral fat 5
years post-partum. Lim et al [11] established a relationship
between abnormal glucose tolerance at one year post-partum and
increased visceral fat in women who had gestational diabetes
mellitus. This was independent of maternal age and BMI.
However, these studies did not have GWG data and they could
not examine whether GWG was associated with diabetes in. The
Mater-University of Queensland Study of Pregnancy (MUSP)
cohort study has available prospectively collected data on GWG
during pregnancy and self reported diabetes 21 years post-partum.
This provides a unique opportunity to examine the association of
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GWG with diabetes in later life. Knowledge of the association
between GWG and subsequent occurrence of diabetes would be
beneficial as this result may be used as a guide to understand the
consequences of varying degrees of GWG with an attempt to slow
the rate of obesity and thereby lessen the risk of future diabetes.
Methods and Materials
The MUSP cohort
Data on GWG, post-partum diabetes and potential confounders
were derived from the MUSP, which is a prospective follow-up
study of 7223 mother-child pairs. At the recruitment, mothers
were on average 18 weeks gestation and received antenatal care at
a major public hospital in Brisbane, Australia, between 1981 and
1983 [12,13]. The original cohort consisted of 7,223 mothers and
their live singleton infants who were born at the study hospital
between 1981 and 1984 and who were not adopted before leaving
hospital. These mothers and offspring pairs have been followed-up
prospectively, with assessments when their offspring were 6
months, 5, 14 and 21 years. The present analyses are limited to
a sub-sample of 3386 mothers for whom complete data was
available on weight gain during pregnancy, pre-pregnancy BMI
and self-reported diabetes 21 years post-partum.
At the first clinic visit (FCV) the response rate was nearly 99%.
At the 6-month follow-up, 6720 women (93%) responded to the
questionnaire. At the 5-year follow-up 5234 mothers (72%)
provided data on their own health. A similar pattern is evident
at the 14-year follow-up with 5185 mothers (72%) responding. At
the 21-year follow-up more than half of the mothers of the original
cohort have provided useable data (Figure 1). Of 3691 women
who provided data at 21 yr follow-up, 230 did not have
information on pre-pregnancy BMI and GWG. A further 75
women who provided diabetes data at 21 yr did not have usable
data from the FCV. 13 reported gestational diabetes, eight women
lost more than 5 kg during pregnancy and seven women gained
more than 35 kg. While it is known that some women do not gain
weight in pregnancy and others gain excessive weight, such
extreme changes are likely to be related to uncommon pathologies.
Maximum recorded weight before 30 week was available for 45
women and after 43 week for two women. Excluding all these
women, the usable sample women are 3386.
Written informed consent from the mothers was obtained at all
data collection phases of the study. Ethics committees at the Mater
Hospital and the University of Queensland approved each phase
of the study. Full details of the study participants and measurements have been previously reported [12,13].
Measurements of Gestational Weight Gain
Main exposure examined was Institute of Medicine (IOM)
recommended categories of GWG, which combine categories of
prepregnancy BMI and gestational weight gain categories [1]. The
2009 IOM recommendations for GWG advise underweight
women (BMI,18.5) to gain 12.5–18.0 kg, normal weight
(18.5#BMI,25) women to gain 11.5–16 kg, and overweight
(BMI$25) women to gain 7–11.5 kg during pregnancy [1]. We
categorized women as having gained inadequate, adequate, or
excess weight according to IOM guidelines [1]. Maternal prepregnancy BMI was calculated as weight in kg divided by height in
meters squared using self-reported pre-pregnancy weight, recorded at baseline from maternal questionnaires, and height measured
at the first clinic visit.
We calculated total GWG as the difference between maximum
recorded weight during pregnancy and self-reported prepregnancy
weight (determined at the first antenatal visit). Maximum weight in
pregnancy was abstracted from the medical chart by an
obstetrician associated with the MUSP. The mean (SD) gestation
was 38.70 (2.62) weeks (median 39 weeks) at maximum recorded
weight. At the FCV women were asked to report their prepregnancy weight; women were also weighed at this clinic. There
was a high correlation between these two measures (Pearson’s
correlation coefficient = 0.95). The mother’s height was measured
without shoes using a portable stadiometer to the nearest 0.1 cm.
Measurement of Diabetes
The main outcome is this study was the self-reported diagnosis
of diabetes mellitus at 21 years post-partum. This information was
gathered using a self-administered questionnaire in which women
were asked ‘‘Have you EVER been told by a doctor that you have
diabetes mellitus (high blood sugars)?’’ with response options ‘‘yes’’
or ‘‘no’’. A positive response to this question was used to indicate
that the woman had incident diabetes mellitus some time during
the 21 years after the pregnancy as women with diabetes mellitus
at the time of the index pregnancy (preexisting or gestational) were
excluded from this study. No information regarding current
therapy for diabetes was available in this study.
Measurements of Confounders or Mediators
In accordance with recommended practice, the potential
confounding or mediating factors are selected on the basis of a
priori knowledge [14] rather than allowing these to be data driven.
Available potential confounders were maternal pre-pregnancy
BMI, maternal age at FCV (in years), maternal educational levels
(did not complete secondary school, completed secondary school,
completed further/higher education), parental ethnic origins
(White, Asian or Aboriginal/Islander), maternal pregnancy
consumption of cigarettes (none, 1–19 or 20 or more per day),
parity (1, 2, 3 or more), TV watching (before pregnancy: ,1 hour,
1 to ,3 hours, 3 to ,5 hours and 5 or more hours) and exercise.
Before pregnancy mothers were asked ‘‘How often they did
physical exercise’’ with response options ‘‘often’’, ‘‘sometime’’, or
‘‘never’’. Breastfeeding (never, ,4 months or 4 or more months)
information was self-reported at the 6 months follow-up was
considered as a mediator. Maternal BMI (based on measured
weight and height) at 21 years post-partum was also considered as
a mediator. Maternal BMI was categorised as normal, overweight
and obese using the WHO standard [15].
Statistical Analysis
Maternal characteristics of women who were included in the
analysis versus those who were excluded were compared. We used
chi-square test for categorical variables and F-test for continuous
variables. The prevalence of diabetes and unadjusted odds ratio
(OR) was presented by the maternal characteristics. The bivariate
association between IOM categories and maternal characteristics
are presented. We used chi-square test to examine this association.
Logistic regression was used to estimate the OR of experiencing
diabetes by 21 years post-partum. We used a series of logistic
regression models to estimate the odds of being diabetic with
adjustment of potential confounding and mediating factors.
Missing items were managed using a multiple imputation method
to impute missing data from the sub-sample of 3386 women. All
the multivariable analyses were conducted for the multiple
imputation data to increase the statistical precision [16]. Model
1 was adjusted for maternal age at the FCV. Model 2 was
additionally adjusted for maternal smoking during the FCV,
respondents educational level at FCV, parity, TV watching and
exercise before pregnancy. Model 3 was additionally adjusted for
the mediating factor breastfeeding. In model 4, to examine
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whether pre-pregnancy BMI modifies the association between
GWG and post-partum diabetes, model 3 results are repeated
stratifying by the maternal pre-pregnancy BMI,25 kg/m2 and
BMI$25 kg/m2. In the final model, we have further adjusted
model 4 by the 21 years post-partum BMI to assess whether
post partum BMI attenuated the associations identified.
Similarly, we repeated this analysis using a series of logistic
regression to examine the association between GWG in continuous scale and diabetes by the 21 year postpartum. For this
analysis, we scaled the weight gain per gestational week to provide
for odds of diabetes by 21 years post-partum at the level of 0.10 kg
GWG/per week. This was chosen as a plausible weight change in
pregnancy and is consistent with a previous publication from this
cohort [17].
All analyses were undertaken using Stata version 11.0 (Stata
inc., Texas).
Results
We found that women who provided information at FCV and
diabetes mellitus 21 years post-partum were more likely to be
older, better educated, with higher incomes, Caucasian, non
smokers during pregnancy, of lower parity and less depressed at
FCV (Table 1). However, these differences are not associated with
the pre-pregnancy BMI and IOM categories of GWG.
Of 3386 women, 11.57% were overweight and 4.31% were
obese before pregnancy. On average, each mother gained
14.96 kg (SD 6.25) weight during pregnancy, with an average of
0.38 kg per week (range: 20.13 o 0.89 kg; SD 0.13) weight gain.
With regard to IOM categories, 839 (24.78%) gained inadequate
weight, 1,353 (39.96%) had adequate weight gain and 1,194
(35.26%) had gained excessive weight during pregnancy. At 21
years post-partum, 8.21% mothers reported a diagnosis of diabetes
made by their doctors. By 21 years post-partum, 30.89% were
overweight and further 30.44% were obese.
Compared to women without self reported diabetes mellitus,
women who did report this condition were more likely to have a
lower level of educational attainment. Maternal age, smoking
before pregnancy, TV watching, exercise, parity and breast
feeding were not associated with diabetes mellitus 21 years postpartum (table 2).
Educational status, race, parity, physical exercise and duration
of breastfeeding were associated with the IOM categories (all pvalues,0.05, table 3). Mothers who were younger (age,20), did
not complete secondary education, were multiparous, were
Aboriginal-Islander and watched TV at least 3 hours/day during
pregnancy and breastfed ,4 months were at greater risk of
gaining excess weight during pregnancy compared to the women
who gained recommended weight.
Figure 1. Selection and recruitment of the MUSP cohort.
doi:10.1371/journal.pone.0075679.g001
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The OR of diabetes at 21 years associated with each IOM
GWG category is estimated using the logistic regression (table 4).
OR (with 95% confidence interval) are presented for 3386 women
in the adjusted model. In the age adjusted model, we found
women who gained excess weight during pregnancy had
1.47(95% CI: 1.11,1.94) times higher risk of experiencing
diabetes at 21 years post-partum compared to the women who
gained adequate weight. Women who gained inadequate weight
during pregnancy had the same risk of diabetes by the 21 year
follow up as women with adequate weight gain. This association
remained robust after adjusting for potential confounding factors
including maternal age, parity, education, pregnancy smoking, TV
watching before pregnancy and exercise. However, adjusting for
current BMI completely attenuated this association. When we
stratified by pre pregnancy BMI category, adjusted models showed
that women who were overweight prior to pregnancy had an OR
of later life diabetes of 1.66 (95% CI: 0.91,3.03), and for women
with a normal weight prior to pregnancy the OR of later life
diabetes was 1.09 (95% CI: 0.78,1.53) (Table 4, Model 5).
Although the effect size at an OR of 1.66 was relatively stronger
than the association found when adjusting for confounders alone
(i.e. model 3), it was not statistically significant (p-value = 0.10). In
model 6, when we have additionally adjusted for the current BMI
at 21 years, the association was further attenuated. In Table 5, we
have estimated the OR of experiencing diabetes for 0.1 kg/week
increase of GWG. The direction and the strength of the
associations are similar to the results presented in table 4.
Discussion
Using a large community based pregnancy cohort study we
found that women who gained excess weight during pregnancy
have had 1.47 times greater risk of experiencing diabetes mellitus
by 21 years post-partum compared to women who gained IOM
recommended weight during pregnancy. This association was not
explained by potential confounders including maternal age, parity,
education, race, smoking, TV watching and exercise. However,
this association was mediated by the current BMI. There was no
association between GWG and subsequent diabetes for the women
who had normal BMI before pregnancy and who gained excess
weight during pregnancy. Taken together, the findings of this
study suggest that women who gain excess weight during
pregnancy are at greater risk of diabetes in later life, and that
this relationship appears to be mediated through the pathway of
weight gain prior to pregnancy, post-partum weight-retention and
obesity.
The association of GWG and long-term post-partum diabetes is
biologically plausible because of the link between GWG and postpartum weight retention or long-term obesity [1]. The phenomena
of weight gain during pregnancy and its link to latter obesity or
diabetes probably relates to a mixture of environmental and
biological changes as well as genetic predisposition. Recent review
and meta analyses found that many women experience difficulty in
losing weight post-partum both in the short and long-term [5].
One possibility is that women who are metabolically prone to
obesity gain excessive weight prior to pregnancy, gain excessive
weight during pregnancy and continue to gain weight throughout
life, which puts them at increased risk of diabetes. We found that
women who were overweight prior to pregnancy were at increased
risk of excess GWG, and also had an increased risk of diabetes in
later life, which supports this hypothesis. It is possible that the
explanation for excessive GWG lies in subtle changes in appetite
regulatory mechanisms, differences in insulin resistance, alterations in leptin signalling, or differences in basal metabolic rate,
which are likely to affect the woman throughout her lifespan, thus
contributing to excess risk for diabetes mellitus. We showed that
markers of an unhealthy lifestyle— smoking cigarettes during
pregnancy, TV watching and lack of physical exercise did not
attenuate the relationship between GWG and long-term diabetes.
However, because we did not have detailed dietary data, we
cannot exclude the possibility that poor dietary behavioral patterns
during pregnancy continued post-partum, thereby contributing to
diabetes. It is also important to note that these women were, on
the whole, relatively lean, and the index pregnancy occurred in the
early 1980s when obesity and gestational diabetes were far less
prevalent and the current food/physical activity environment was
less obesogenic.
The major strength of this study is that findings are based on
information from a large cohort of women, followed for the longest
period of time in the literature to date. However, there are several
limitations in this study which we need to be considered. The
diagnostic and screening criteria for gestational diabetes were
controversial in the early 1980s [18]. Therefore, according to
current standards, some women might have had undiagnosed
diabetes mellitus during the pregnancy at that time. If these
women were excluded from the analyses, this might attenuate the
association between GWG and post-partum diabetes. Further, we
have used self-reported of diabetes mellitus diagnosed by a doctor,
which might underestimate the diabetes cases in our study. The
recent AusDiab study reported that half of the women who were
identified with diabetes mellitus were undiagnosed [19]. Margolis
et al. [20] validated the use of self administered questionnaire to
assess the prevalence/incidence diabetes in middle aged women.
By comparing the self-reported diabetes with medication inventories and fasting glucose measurements, they found self-reported
prevalent and incident diabetes was consistent with medication
inventories and fasting glucose. As we did not have GWG
information for subsequent births, it is also possible that women
who had gestational diabetes mellitus in a subsequent pregnancy
may be included in the group of women who reported diabetes

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mellitus in the 21 years after the index pregnancy. Thus, it is
important that our findings are replicated in other large
population based studies with objective measures of diabetes
mellitus and gestational diabetes mellitus based on fasting glucose
or glucose tolerance studies.
The MUSP sample comprises effectively all consecutive births
of public patients over 3 years, ensuring a broad cross section of
mid to lower socio-economic status births. Participants were not
selected on the basis of any physical or social characteristic. The
MUSP is not representative of all Australian families. However,
there is no biological reason to suspect that the associations we
found in this study should differ substantially from other
populations. Many of the epidemiological associations that inform
public health practice are based upon cohort studies that are
similarly unrepresentative of the overall population. Examples
include the effect of smoking on lung cancer and cardiovascular
disease (a cohort of British Male doctors), the effect of cholesterol
on cardiovascular disease (the Framingham study of middle aged
US adults), and the effects of hypertension on cardiovascular
disease (British Men).
The loss to follow-up in the MUSP cohort was considerable
[13]. In general, non-participant mothers were more likely to be
from families with low income at birth, to have mothers who
smoked throughout their pregnancy, had poorer mental health,
and to have mothers and fathers with lower educational
attainment [12,13]. The disproportionate loss to of follow-up
may lead to underestimates of the strength of associations (that is
the loss of higher BMI mothers and children). We have previously
used three strategies to assess the impact of attrition on our
estimates of association. Firstly, we used multiple imputation,
which did not alter the strength and direction of our findings in
any material way. Secondly, we used sensitivity analyses modelling
a wide variety of associations to assess the impact of those lost to
follow-up [13]. Once again, these analyses did not reveal that loss
to follow up substantially altered our findings. Finally, we
conducted comparative analyses using data from different cohort
studies with different levels of attrition, and were able to conclude
that substantial variations in loss to follow-up has very little impact
on the findings [21]. Another limitation of this study is we only
used IOM 1993 categorization of GWG. Recently IOM reviewed
their guidelines [1] and recommended rates of weight gain in 2nd
and 3rd trimester as well. As we do not have the record of trimester
specific weight gain, we could not extend our analyses in this way.
The main implication of this limitation is that we are unable to
examine whether trimester specific weight gain has any specific
impact on the development of diabetes. This would be an
interesting area of further research.
In summary, this is the first study to show that women who gain
excess gestational weight have an increased risk of developing
diabetes mellitus later in life through the pathway of post-partum
weight retention and obesity. Overall, this finding is consistent to
the increasing evidence showing that excess GWG predict post

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partum weight retention and higher BMI in the short and longterm [5] which contributes to metabolic dysfunction and diabetes
[7–9]. Our findings need to be replicated in other large cohort
studies. This study adds weight to the argument that excessive
weight gain during pregnancy, particularly for overweight women
is not only important in the short term, but has long term health
implications.
Acknowledgments
We thank all participants in the study, the MUSP data collection team, and
data manager, University of Queensland who has helped to manage the
data for the MUSP.
Author Contributions
Conceived and designed the experiments: AAM GW JN MO. Performed
the experiments: AAM GW. Analyzed the data: AAM GW. Contributed
reagents/materials/analysis tools: AAM MO JN MM LC. Wrote the
manuscript: AAM MM MO GW JN LC.
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