Pre-pregnancy weight change and incidence of gestational diabetes mellitus: A finding from a prospective cohort study

https://doi.org/10.1016/j.diabres.2016.12.014Get rights and content

Highlights

  • BMI at 18–23 years is closely associated with increased risk of GDM.

  • Pre-pregnancy weight gain over the reproductive course of life is a strong risk factor for GDM.

  • Women even in a normal range of BMI need to prevent weight gain prior to pregnancy.

Abstract

Aims

In a population-based cohort study we examined the associations between early adult pre-pregnancy weight change and the risk of gestational diabetes mellitus (GDM).

Methods

The study included 3111 women from the 1973–78 cohort of the Australian Longitudinal Study on Women’s Health. These women have been surveyed regularly since 1996. Women without diabetes and GDM were followed-up between 2003 and 2012. Generalized estimating equations were used to assess the effect of baseline (1996, mean age 20 years) and pre-pregnancy body mass index (BMI) and the pre-pregnancy weight changes on the incidence of GDM. The full models were adjusted for sociodemographic and lifestyle factors.

Results

From 2003 to 2012, 229 GDM cases (4.4%) were reported in 5242 pregnancies. Relative to normal BMI women, obese women at baseline (RR: 1.8, 95% CI: 1.1, 2.8) and prior to pregnancy (RR: 2.7, 95% CI: 2.0, 3.6) were at greater risk of GDM. Weight gains prior to each study pregnancy were strongly associated with increased GDM risk with an adjusted RR ranging from 2.0 to 2.9. Within under/normal range of BMI, women with a moderate/high (>2.5%/year) weight gain had 2.7 (95% CI: 1.3, 5.5) times the risk of GDM compared with women with stable weight.

Conclusions

Early adult weight gain, even within normal BMI range, is an important risk factor for the development of GDM. Weight gain prevention from early adulthood to prior to pregnancy appears to be the main strategy to prevent the incidence of GDM.

Introduction

Gestational diabetes mellitus (GDM), a state of impaired glucose tolerance recognised for the first time in pregnancy, is one of the most frequent pregnancy complications associated with higher maternal and perinatal adverse outcomes [1]. The prevalence is increasing mainly as a result of the rising proportion of women with pre-pregnancy obesity, sedentary lifestyles and advanced maternal age at birth [2], [3]. Women with GDM are more likely to develop type 2 diabetes in later life compared to women without GDM [4].

The cross sectional association between body mass index (BMI) and GDM is well established [5]. Although evidence of a causal relationship is scarce, in a meta-analysis of observational studies, the risk of development of GDM ranged from a two- to fivefold increase for women who were overweight and severely obese prior to pregnancy, respectively [6]. A number of studies [7], [8], [9], [10] have also showed that weight gain over the life course has substantial effect on the development of diabetes and other cardiovascular risks in non-pregnant women and men. However, there are only a few studies [11], [12] of the relationship between early adult pre-pregnancy weight change and the risk of GDM.

In the life course, young adults (20–29 years of age) are at higher risk of increased weight gain [13]. Changes in the early adult pre-pregnancy weight over the reproductive years of the life course may have more important effect than the immediate pre-pregnancy weight. The women who develop GDM have been shown to have had nearly a twofold rate of weight gain prior to pregnancy than non GDM women [11]. Even in a normal range of BMI, a pre-pregnancy weight gain has been associated with an elevated risk of GDM [12], [14]. Weight gain/retention between consecutive pregnancies has also been found to be linked with the increased risk of GDM [14], [15]. However, the existing scarce studies were limited to nursing professional mothers whose childhood body shape and weight (at 18 years) were reported retrospectively and subsequent adult weights were collected over a short interval [12]. The other studies collected weight trajectories in a single retrospective interview [11] or measured only inter-pregnancy weight change [14], [15] rather than over the reproductive course of life. These studies were further limited to clinical populations and lacked adjustment for potential confounders such as diet, and physical activity, a fact acknowledged by the authors [11].

We therefore primarily aimed to examine whether the changes in early adult pre-pregnancy weight from baseline (1996, 18–23 years of age) to 25–30 years of age (2003) and to each study pregnancy (with children born between 2003 and 2012) are associated with the development of GDM using data from a broadly representative population-based cohort study of Australian women. As a secondary objective, we investigated the effect of early adult pre-pregnancy weight change on the subsequent risk of GDM in women within different BMI categories.

Section snippets

Data source and participants

The Australian Longitudinal Study on Women’s Health (ALSWH) is an ongoing large longitudinal population-based study examining the health of over 58,000 Australian women. In 1996, three cohorts of women born in 1973–78 (‘young’, aged 18–23 at baseline), 1946–51 (‘mid-age’, aged 45–50 at baseline), and 1921–26 (‘older’, aged 70–75 at baseline) were randomly selected from the national Medicare health insurance database, which includes all Australian citizens and permanent residents. Random samples

Results

A total of 3111 women who reported 5242 pregnancies between S3 and S6 (mean 1.7 pregnancies per women) were included. Of these pregnancies, 229 new cases of GDM (4.4%) were reported. The mean age of women at the baseline was 20 (SD 1.5) years. About three fifths (58.8%) of women were urban residents. The majority of women had completed up to year 12 (66.6%), were never married (82.9%), and were nulliparous (97.4%). Among the study population, 9.3%, 14.6% and 4.4% of women were underweight,

Discussion

We found baseline (mean age 20 years) and pre-pregnancy obesity (on average approximately a year before a pregnancy) to be significantly associated with increased GDM risk, after adjustment for potential confounders. The association was stronger with the latter as pre-pregnancy obesity is the closest measure to the event of pregnancy. While others have shown inconsistencies between early adult obesity and latter GDM risk [11], there is a general consensus in the relationships of pre-pregnancy

Author contributions

A.A.A designed the study, performed the analysis, and drafted the manuscript; L.R.T and G.D.M contributed to the design of the study, analyses, interpretation of the results, and critical revision of the manuscript for important intellectual content. All authors have approved the final version.

Conflict of interest

The authors declare that they have no conflict of interests to disclose.

Acknowledgements

The research on which this paper is based was conducted as part of the ALSWH by the University of Queensland and the University of Newcastle. We are grateful to the Australian Government Department of Health for funding and to the women who provided the survey data. A.A.A is supported by an International Postgraduate Research Scholarship and a UQ Centennial scholarship. G.D.M is funded by an Australian Research Council Future Fellowship (FT120100812). The founder has no role in study design

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