Metformin does not improve pregnancy outcomes in obese women

Researchers conducted a randomised controlled trial of metformin in pregnant obese women, but the drug did not reduce birthweight or pregnancy complications. In the image, a doctor checks the heart rate of a foetus

Maternal obesity in pregnancy can adversely affect mother and child. Offspring have increased birthweight, and in adulthood they have an increased risk of obesity and a 35% increase in risk of death. Maternal insulin resistance and hyperglycaemia are implicated in these outcomes, so a new trial examines the impact of the insulin-sensitising drug metformin on obese, pregnant women.

In all, 449 obese women with normal glucose tolerance were randomly assigned metformin 500–2500mg daily or placebo
from the second trimester until delivery. Metformin had no significant impact on babies’ birthweight or on a composite end point of miscarriage, termination of pregnancy, stillbirth or neonatal death.

Metformin was ass
ociated with a reduction in inflammatory markers in pregnant women, however, and the babies will continue to be monitored for longer-term treatment effects, say the study authors in
The Lancet
(online, 9 July 2015)

  • This research briefing was amended on 13 August 2015 to clarify that a reduction in inflammatory markers was seen in pregnant women.


[1] Chiswick C, Reynolds RM, Denison F et al. Effect of metformin on maternal and fetal outcomes in obese pregnant women (EMPOWaR): a randomised, double-blind, placebo-controlled trial. Lancet Diabetes Endocrinol 2015. doi:10.1016/S2213-8587(15)00219-3.

Last updated
The Pharmaceutical Journal, PJ, 25 July/1 August 2015, Vol 295, No 7872/3;295(7872/3):DOI:10.1211/PJ.2015.20069022

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