There’s not much evidence on the risk of birth defects with medications used to treat opioid use disorder (OUD) during pregnancy. But a recent study found that treating OUD with buprenorphine during the first trimester was linked with an 18% lower relative risk and about a 1% lower absolute risk of congenital malformations compared with methadone treatment. The analysis, published in JAMA Internal Medicine, was based on data from more than 13 000 pregnancies.