Key PointsQuestionAre policies mandating warning signs regarding the harms of cannabis use during pregnancy associated with beliefs and behaviors?FindingsThis cross-sectional study used data from 2063 US-based survey respondents who were or had recently been pregnant and found that, among people who used cannabis during pregnancy, living in a state with a warning signs policy was significantly associated with believing use was safe and should not be punished; among those who did not use cannabis, warning signs policies were significantly associated with believing use was not safe and should be punished. There were no associations of living in a state with a mandatory warning sign policy with using cannabis during pregnancy.MeaningThese findings suggest that while warning signs policies were not associated with believing use was less safe among pregnant individuals who used cannabis during pregnancy, policies were associated with support for punishment among people who did not use cannabis.