Abstract Background Cannabis use during pregnancy is increasingly common and is associated with adverse health outcomes for pregnant individuals and their offspring. Identifying preconception factors that are associated with prenatal cannabis use is critical to inform early prevention and intervention. This study tested whether frequency of preconception cannabis use was associated with cannabis use during early pregnancy using data from a large healthcare system with universal screening for cannabis use. Methods This observational study included pregnant individuals in Kaiser Permanente Northern California (KPNC) who self-reported any cannabis use (daily, weekly, or monthly or less) during the year before pregnancy from 2011 to 2022 (excluding...