Gestational diabetes mellitus (GDM) in the first-reported pregnancy modifies association between interpregnancy-weight-change and GDM risk in the subsequent pregnancy

Abstract

Background

Weight change between pregnancies affects gestational diabetes mellitus (GDM) risk in subsequent pregnancies. However, it is unclear whether this impact differs based on the individual’s GDM status in a prior pregnancy.

Objectives

To evaluate whether prior GDM status modifies the association between interpregnancy-weight-change and GDM risk in a subsequent pregnancy.

Study Design

Using Vanderbilt Health's de-identified electronic health record, we identified 4574 individuals with at least 2 recorded pregnancies, with information available on GDM status and body mass index (BMI) at GDM screening. We computed interpregnancy-weight-change as the change in BMI at GDM screening between 2 consecutive-reported pregnancies. Using multivariable linear probability and binomial regression models, we evaluated the association between interpregnancy-weight-change and GDM risk in the second pregnancy, overall, and stratified by GDM status in the first pregnancy. We tested for effect measure modification by calculating the interaction contrast (IC) across the risk differences (RDs). We reported predicted risks for GDM, RD, and Differences in RD in the subsequent pregnancy between patients with and without GDM in their first-recorded pregnancy.

Results

On average, patients gained weight (BMI increased by 0.9 kg/m²) between pregnancies and were more likely to have GDM in their second-recorded pregnancy (6.0% vs 4.4%). Individuals with GDM in their first pregnancy were more likely to have GDM in the second pregnancy compared to individuals without GDM in the first pregnancy (30.2% vs 5.0%). The excess risk of GDM for individuals who gained 5 BMI kg/m² (∼29 pounds [lbs] in patients with BMI of 27.1 kg/m² and height of 5 feet 4 inches) was substantially higher in those with GDM in their first pregnancy (RD=28.0%; 95% CI=19.1%, 36.9%) compared to those without GDM in their first pregnancy (RD=5.6%; 95% CI=3.8%, 7.4%). The IC was 22.4% (95% CI=13.4%, 31.5%; P<.001) across the RDs,. Similarly, the impact of weight loss (2 BMI units ∼ 12 lbs) on GDM risk reduction in the subsequent pregnancy was greater in individuals with prior GDM in their first pregnancy (RD=−3.9%; 95% CI=−0.7%, −7.2%), than among individuals without prior GDM in their first pregnancy (RD=−1.0%; 95% CI=−0.1%, −1.9%), with some evidence for effect measure modification (IC=−2.9%; 95% CI=−6.3%, 0.5%; P=.091). However, the predicted risk of subsequent GDM in women with prior history of GDM remains high (17.9% risk with 12 lbs weight loss and 15.4% with 29 lbs weight loss) despite substantial risk reduction.

Conclusion

Interpregnancy BMI increase is associated with an elevated risk of GDM in subsequent pregnancies for all individuals but is substantially pronounced in individuals with a history of GDM. Individuals with prior GDM may mitigate their risk through weight loss, but not sufficiently to reduce it to levels similar to those without GDM in their previous pregnancy. In counseling patients with a history of GDM considering a subsequent pregnancy, it is important to encourage weight loss for various reasons, while also emphasizing that the risk of GDM remains high even with weight loss.