Homicide is a leading cause of death among women who are pregnant and up to one year postpartum in the United States. Most incidents are perpetrated by an intimate partner with a firearm. Some states have implemented laws that prohibit firearm possession by perpetrators of domestic violence and, in some instances, include explicit statutory language mandating relinquishment of firearms once a person has become prohibited from possessing them. We examined the impact of these policies on state-level rates of homicide among pregnant and postpartum women during the period 2011-19. We found that state laws prohibiting possession of firearms and requiring relinquishment of firearms by people convicted of domestic violence-related misdemeanors were associated with substantial reductions in homicide of pregnant and postpartum women. State policy makers should consider further strengthening domestic violence-related firearm regulations and their enforcement to prevent homicide of pregnant and postpartum women.