As legal marijuana has become more common, its use during pregnancy has also grown exponentially, despite a growing body of strong scientific evidence that it can harm children. A new study published in JAMA Pediatrics builds on previous research linking prenatal cannabis exposure to behavior problems when children were 9 to 10 years old. The new analysis—which tracked some 12,000 children as they grew into young adults—connected prenatal cannabis exposure to mental disorders into adolescence, including attention, social, and behavioral difficulties, which could raise the risk of mental health disorders and substance use in later adolescence. As more and more states legalize cannabis, and its consumption becomes mainstream and considered largely benign, its use among women who are pregnant doubled to 12 percent between 2002 and 2017, the latest year that data is available. Doctors and public health officials continually warn women of the risk of using marijuana during pregnancy, even as cannabis dispensaries market their products as a way to curb morning sickness of nausea. One immediate consequence of marijuana use during pregnancy: studies show it is likely to lead to early and potentially dangerous delivery. As marijuana use clearly poses risks for the pregnant person and the child’s development, we need a more robust campaign among healthcare professionals to educate patients while the government must crack down on marijuana retailers who target people who are pregnant.