Lessons learned from lifestyle prevention trials in gestational diabetes mellitus.

Gestational diabetes mellitus (GDM) is associated with an increased risk of adverse outcomes for mother and infant both at birth and later in life. A large body of evidence is now available relating to antenatal prevention of GDM. Overall, despite some individual trials of a variety of lifestyle interventions revealing benefit, many more have shown no effect from the second trimester onwards, even with significant gestational weight gain limitation. At-risk women often seem reluctant to engage in lifestyle changes and frequently cannot adhere to recommended interventions even within a clinical trial setting. Many trials have not considered the heterogeneity of diabetes first discovered in pregnancy, something of importance into the future. Future work should focus on designing interventions acceptable to the population at risk, whether those taking place before or during the first trimester of pregnancy are effective, and whether greater individualization can identify those women most likely to benefit.