Should we continue or stop insulin sensitizing drugs during pregnancy?

Purpose of review The use of insulin sensitizing drugs such as metformin in polycystic ovary syndrome has been increasingly popular and validated by systematic reviews. There has also been an interest in the use of metformin for gestational diabetes. However, administration of metformin to prevent miscarriage is controversial and widespread use of this drug in early pregnancy requires investigation. Recent findings There are claims that miscarriage and gestational diabetes are more common in polycystic ovary syndrome and that use of insulin sensitizers improves outcomes dramatically. This review suggests there is no evidence for increased risk of miscarriage solely due to polycystic ovary syndrome and that there are insufficient data for promoting therapy with metformin. There is some reason for use of metformin in mid-pregnancy for gestational diabetes but better evidence from randomized controlled trials is urgently needed. Summary The use of metformin in early pregnancy for reducing the risk of miscarriage should be avoided outside of the context of properly designed prospective randomized trials. Safety in early pregnancy appears to be reassuring but not completely proven. The use of metformin in mid-pregnancy for gestational diabetes appears more logical but also needs adequate trials before general use is advocated.