In a study of 300,993 pregnancies, California's recreational cannabis legalization was associated with a significant 10% increase in prenatal use, driven entirely by women in jurisdictions that allowed adult-use retailers.
Prenatal care providers; cannabis policy makers considering retail regulations.
21% increase in prenatal cannabis use in jurisdictions that allowed dispensaries
What the researchers found
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).
Why it matters
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 numbers in context
300,993 pregnancies. Pre-RCL use: 4.5% (2012) to 7.1% (January 2018). Post-implementation: 8.6% (February 2018). Level change at RCL passage: RR 1.03 (not significant). Level change at implementation: RR 1.10 (95% CI: 1.04-1.16). Jurisdictions allowing retailers: RR 1.21 (1.10-1.33). Jurisdictions banning retailers: RR 1.01 (0.93-1.10).
How the study worked
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.
What this study cannot tell us
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.
How to read the evidence
Strong: very large population-based study with objective toxicology data, interrupted time series design, and natural experiment comparing jurisdictions with and without retail access.
When this study was published
2024 study using 2012-2019 data.
The bigger picture
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.
Questions still open
- Would targeted interventions in prenatal care near dispensary locations reduce prenatal cannabis use? Does the type of cannabis products available in legal retail (e.g., high-potency concentrates) matter for prenatal use patterns?
Common questions
Did just legalizing cannabis increase prenatal use?
How was cannabis use detected?
Read the original research
Cannabis Use During Early Pregnancy Following Recreational Cannabis Legalization.
JAMA health forum, 5(11), e243656
Citation
Young-Wolff, Kelly C; Slama, Natalie E; Avalos, Lyndsay A; Padon, Alisa A; Silver, Lynn D; Adams, Sara R; Does, Monique B; Ansley, Deborah; Castellanos, Carley; Campbell, Cynthia I; Alexeeff, Stacey E. (2024). Cannabis Use During Early Pregnancy Following Recreational Cannabis Legalization.. JAMA health forum, 5(11), e243656. https://doi.org/10.1001/jamahealthforum.2024.3656
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