Most U.S. states have policies targeting alcohol or drug use during pregnancy. But ANSIRH research shows that at best, most policies do not affect use during pregnancy or birth outcomes. At worst, some alcohol and drug policies lead to increases in low birthweight and preterm birth, costing millions of dollars each year. They can also lead to decreases in prenatal care use. We’ve found that policies targeting alcohol and drug use during pregnancy can undermine access to health care and other supports for pregnant people.