Weight gain in pregnancy: can metformin steady the scales?

Abstract

Objective

Metformin has been associated with modest weight reduction in the non-pregnant population. Our hypothesis is that metformin exposure will lead to a higher incidence of appropriate weight gain during pregnancy.

Study Design

This was a retrospective cohort study in a single center between 2009 and 2019. We included all pregnant women with type 2 diabetes or prediabetes. We compared women exposed to metformin in any trimester. The primary outcome was appropriate weight gain defined by the Institute of Medicine guidelines. Secondary outcomes included excessive weight gain, weight loss, suspected fetal growth restriction (FGR), and mean birth weight. Adjusted odds ratios or group differences were calculated using logistic or linear regression, controlling for confounders.

Results

Of 41,472 deliveries during the study period, 511 pregnancies met inclusion criteria. 284 pregnancies had no metformin exposure; 227 did have metformin exposure, of which 169 (72.2%) were initiated on metformin in the first trimester. Women exposed to metformin in any trimester were statistically not more likely to have appropriate weight gain (aOR 1.53 (95% CI 1.00–2.34, p = .048), but did have less excess weight gain (aOR 0.45, 95% CI 0.30–0.66, p < .001), and more maternal weight loss (aOR 2.17, 95% CI 1.18–3.98, p = .012) than the unexposed group. Women exposed to metformin in the first trimester of pregnancy were less likely to have excess weight gain (aOR 0.39, 95% CI 0.25–0.61, p < .001) and more likely to have maternal weight loss (aOR 2.56, 95% CI 1.30–5.07, p = .007) than the unexposed cohort. There was no difference in FGR (5.3% vs 2.5% p = .094) or mean birth weight (3235.6 vs 3352.4 gm p = .122) in the metformin exposed group vs non-exposed groups, respectively.

Conclusions

Metformin exposure in pregnancy was associated with less excess weight gain and a higher rate of weight loss. There was no difference in FGR or mean birth weight in metformin exposed neonates. This suggests that metformin may help avoid excess weight gain and its associated comorbidities.

Keywords:

• Diabetes
• weight gain
• obesity

Acknowledgements

We would like to acknowledge Kathy Gollmar, Carla Griffin, and Ancilla Partners for their support and assistance with data extraction from PeriData.Net for this project (employed by UnityPoint Health-Meriter). PeriData.Net is a comprehensive birth registry maintained by Ancilla Partners, Inc. This registry provides process and outcome measure results as well as birth level data on how well a given hospital and its providers are administering quality of care before, during, and after the birthing lifecycle. We would finally like to acknowledge Robert Koehler for assisting with the literature review and article acquisition (employed by UnityPoint Health-Meriter).

Disclosure statement

No potential conflict of interest was reported by the author(s).