Metformin During Pregnancy May Reduce Maternal Weight Gain for Obese Women

(HealthDay News) — For obese women, metformin administration during pregnancy is associated with reduced maternal weight gain, without reducing median neonatal birth weight, according to a study published in the New England Journal of Medicine.

Argyro Syngelaki, PhD, from King’s College Hospital in London, and colleagues randomly assigned pregnant women without diabetes with a body mass index (BMI) of greater than 35 kg/m² to metformin or placebo (225 in each group) from 12 to 18 weeks of gestation until delivery. Data were analyzed for 202 women in the metformin group and 198 in the placebo group.

The researchers observed no significant difference in the median neonatal birth-weight z score between the groups (0.05 in the metformin group vs 0.17 in the placebo group; P=.66). 

Compared with the placebo group, the metformin group had lower median maternal gestational weight gain (4.6 vs 6.3 kg; P<.001) and lower incidence of preeclampsia (3.0% vs 11.3%; odds ratio [OR]=0.24; P=.001). 

The metformin group had higher incidence of side effects compared with the placebo group. 

No significant differences were observed between the groups in the incidence of gestational diabetes, large-for-gestational-age neonates, or adverse neonatal outcomes.

“Among women without diabetes who had a BMI of more than 35, the antenatal administration of metformin reduced maternal weight gain but not neonatal birth weight,” the researchers wrote.


  1. Syngelaki A, Nicolaide KH, Balani J, et al. Metformin versus Placebo in Obese Pregnant Women without Diabetes Mellitus. N Engl J Med. 2016;374:434-443. doi:10.1056/NEJMoa1509819.