Acute Care for Cannabis Use During Pregnancy Nearly Doubled After Legalization in Ontario

The mean quarterly rate of cannabis-related acute care during pregnancy rose from 11.0 to 20.0 per 100,000 pregnancies after legalization (IRR 1.82). Mental health acute care decreased and non-cannabis substance use care did not change, serving as controls. Cannabis-related acute care during pregnancy was associated with 9.7-fold higher odds of hyperemesis gravidarum, 1.93-fold higher odds of preterm birth, and 1.94-fold higher odds of NICU admission.

Population-based repeated cross-sectional study in Ontario, Canada (Jan 2015-Jul 2021). Segmented regression comparing cannabis-related acute care trends to mental health and non-cannabis substance use controls. Multivariable logistic regression for neonatal outcomes.

With cannabis legalization spreading globally, understanding impacts on vulnerable populations like pregnant people is critical. While the relative increase was large, the absolute numbers remained small. The association with preterm birth and NICU stays adds urgency to prenatal screening discussions.

The gradual rather than immediate increase after legalization suggests a normalization effect: as cannabis becomes more socially acceptable, more pregnant people may use it or be more willing to disclose use. The strong link to hyperemesis gravidarum aligns with emerging research on cannabinoid hyperemesis in pregnancy.

Cannot determine if the increase reflects more cannabis use, more willingness to disclose, or better clinical detection. Observational design cannot establish whether cannabis caused the adverse neonatal outcomes. COVID-19 overlapped with part of the study period.