Metformin linked to reduced preterm birth risk in high-risk pregnancies, new research shows

Research from Monash University suggests that metformin, a common diabetes medication, may lower the risk of preterm birth among women with high metabolic risks, prompting calls for targeted trials to explore its potential benefits.

Metformin, a low-cost diabetes medicine, may do more than control blood sugar in pregnancy. Researchers at Monash University say it was associated with a lower risk of preterm birth among women at high metabolic risk, even though it did not prevent gestational diabetes overall.

The findings, published in NEJM Evidence, drew on individual patient data from seven randomised, placebo-controlled trials covering 2,297 pregnancies. According to Monash University, women given metformin had 35 per cent lower odds of delivering before 37 weeks than those given placebo. The rate of births before 34 weeks was also roughly halved, falling from 4.4 per cent to 2.2 per cent.

Associate Professor Aya Mousa of the Monash Centre for Health Research and Implementation said women taking metformin gave birth earlier far less often, and that pregnancies which still ended prematurely lasted an average of 11 days longer. She said the treatment’s potential effect on preterm birth should be tested in trials designed specifically for that purpose, including studies that examine when the drug should be started.

The work is part of the Metformin in Pregnancy Study, an international collaboration led by Monash researchers that is pooling data from trials around the world. Professor Helena Teede said the larger dataset helps fill a long-standing evidence gap, because smaller studies have produced mixed results and have not been large enough to settle questions about metformin’s role in pregnancy.

For now, the picture remains mixed. The drug did not improve several other pregnancy outcomes, including birth weight, high blood pressure, pre-eclampsia, labour induction or Caesarean section, and it did not stop gestational diabetes overall. Even so, researchers say the signal on preterm birth is strong enough to justify further investigation, alongside ongoing work on the long-term effects of metformin exposure during pregnancy.