Women with polycystic ovary syndrome, but no diagnosed diabetes, are less likely to have a late miscarriage or preterm birth if they take metformin either before or during pregnancy, a study suggests.

The authors, who believe they are the only researchers worldwide investigating the use of metformin in PCOS to reduce pregnancy-related conditions, say the results suggest that the drug may reduce late miscarriage and preterm delivery when used during pregnancy.

However, two expert commentators say the results imply that taking the drug before conception may be the way to go. 

In the PregMet2 study 487 pregnant women diagnosed with PCOS were randomised to either 2g of metformin or placebo daily. The participants started taking the intervention at a median of 10.7 weeks gestation and continued until delivery.