The supplemental material provides detailed information on the methods used to screen for prenatal substance use, particularly cannabis, and the criteria for identifying maternal health outcomes during pregnancy. The study utilized urine toxicology tests ordered during the first prenatal visit, typically around 8-10 weeks of gestation, to screen for substances such as THC/cannabis, alcohol, opioids, amphetamine/methamphetamine, cocaine, barbiturates, and benzodiazepines. Confirmatory testing was performed using advanced analytical techniques for all positive initial immunoassay results. The study also includes a list of ICD-9/10 diagnosis codes and other diagnostic criteria used to identify maternal health outcomes, such as severe maternal morbidity, weight gain during pregnancy, and gestational diabetes. Additionally, the socio-demographic characteristics of the pregnancies included in the study cohort are compared with those excluded due to missing prenatal cannabis use data, and the frequency of prenatal cannabis use is analyzed in relation to various pregnancy characteristics and outcomes, including live birth, stillbirth, and therapeutic abortion. The models used to analyze these data are adjusted for various covariates to ensure statistical significance.The supplemental material provides detailed information on the methods used to screen for prenatal substance use, particularly cannabis, and the criteria for identifying maternal health outcomes during pregnancy. The study utilized urine toxicology tests ordered during the first prenatal visit, typically around 8-10 weeks of gestation, to screen for substances such as THC/cannabis, alcohol, opioids, amphetamine/methamphetamine, cocaine, barbiturates, and benzodiazepines. Confirmatory testing was performed using advanced analytical techniques for all positive initial immunoassay results. The study also includes a list of ICD-9/10 diagnosis codes and other diagnostic criteria used to identify maternal health outcomes, such as severe maternal morbidity, weight gain during pregnancy, and gestational diabetes. Additionally, the socio-demographic characteristics of the pregnancies included in the study cohort are compared with those excluded due to missing prenatal cannabis use data, and the frequency of prenatal cannabis use is analyzed in relation to various pregnancy characteristics and outcomes, including live birth, stillbirth, and therapeutic abortion. The models used to analyze these data are adjusted for various covariates to ensure statistical significance.