Summary: Cannabis refers to all products derived from the plants Cannabis sativa, Cannabis indica, and Cannabis ruderalis and is the most commonly used illicit drug under U.S. federal law. With increasing social acceptability, accessibility, and legalization in many states, the prevalence of cannabis use among pregnant and lactating individuals has increased significantly. Substance use in pregnancy, including cannabis use, has been associated with adverse outcomes such as spontaneous preterm birth, low birth weight, and developmental delay. Obstetrician–gynecologists and other obstetric health care professionals should be aware of the possibility of pregnant and lactating patients’ use of cannabis and be prepared to counsel and screen all patients and use evidence-based strategies to reduce cannabis use (link is open access).