Prenatal Cannabis Use Jumped After California Legalized Recreational Sales, Especially Where Dispensaries Opened

Prenatal cannabis use rose from 4.5% in 2012 to 7.1% before legalization implementation, then jumped to 8.6% after implementation (level change RR 1.10, 95% CI: 1.04-1.16). The increase was detected by both toxicology testing and self-report. In jurisdictions allowing adult-use retailers, the increase was 21% (RR 1.21), while jurisdictions banning retailers showed no change (RR 1.01).

Population-based interrupted time series study of 300,993 pregnancies (236,327 unique individuals) in Kaiser Permanente Northern California from January 2012 to December 2019. Cannabis use was universally screened by self-report and urine toxicology at ~8-10 weeks gestation. Poisson regression models adjusted for age, race/ethnicity, and neighborhood deprivation.

This is the largest and most rigorous study to date linking recreational cannabis legalization directly to increased prenatal use. The finding that the increase was concentrated in areas with dispensaries, not just with legalization itself, suggests that retail access -- not just legal status -- drives prenatal cannabis use.

The distinction between legalization and commercialization matters enormously. Simply changing the legal status showed no significant effect, but opening retail stores did. This suggests that jurisdictions considering legalization could potentially mitigate prenatal use increases through zoning restrictions on dispensary locations.

Single health system in Northern California may not generalize to all populations. Urine toxicology detects recent use but cannot distinguish occasional from heavy use. The pre-legalization upward trend in prenatal use means some increase would have occurred regardless of legalization.