The incidence of gestational diabetes and type 2 diabetes in pregnancy is increasing at an alarming rate, while adverse pregnancy outcomes remain high.1 For this reason, clinicians and patients welcome randomized clinical trials (RCTs) to explore ways for improving outcomes in these vulnerable populations. In this issue of JAMA and in an issue of JAMA published in October 2023, 2 trials investigate the role of metformin during pregnancy to improve adverse outcomes: one trial in women with gestational diabetes and one trial in those with type 2 diabetes.