Early pregnancy cannabis use high in states with recreational legalization

Recreational cannabis legalization in California was linked to increased rates of cannabis use during early pregnancy among women—particularly in jurisdictions in the state that allowed adult-use retailer businesses to open.

The findings from the population-based time-series study highlights a potential public health worth addressing proactively in obstetrician / gynecology clinics in states where recreational cannabis may potentially become legalized going forward.

A team of investigators from the University of California, San Francisco—led by Kelly C. Young-Wolff, PhD, MPH, from the division of research at Kaiser Permanente Northern California—sought any correlations between recreational cannabis legalization and prenatal cannabis use rates via self-report and urine toxicology testing. They additionally wanted to observe any more distinct correlations prenatal cannabis use and local policies banning or allowing cannabis retail.

Their setting was California, where cannabis was legalized in November 2016. The team observed that the prevalence of self-reported cannabis use has more than doubled in the US since 2002.

“Pregnant individuals report using cannabis to treat mental health and physical symptoms, and some view cannabis as a potentially safer option than prescription medications,” investigators wrote. “However, prenatal cannabis use is associated with an increased risk of adverse neonatal outcomes and maternal pregnancy outcomes and may also be associated with offspring neurodevelopment. National medical organizations recommend that clinicians screen for prenatal cannabis use, educate patients about potential risks, and recommend abstinence during pregnancy.”

Their time-series analysis of the real-world population used data from pregnancies to occur at Kaiser Permanente Northern California. The data included screen results from universal pregnancy cannabis use tests—both self-report and toxicology—between January 2012 – December 2019.

Young-Wolff and colleagues examined California’s legalization and the implementation of legal sales in 2018 with a 1-month lag. They additionally assessed local policies for or against medical retailers prior to recreational use legalization, and adult-use retailers, post-recreational use legalization.

Prenatal cannabis use was based on screening at entrance of prenatal care (8 – 10 weeks’ gestation) and were defined by either positive urine toxicology and self-report, lone toxicology, or lone-report.

The team’s data included 300,993 pregnancies from 236,327 individuals over the time period. Patients were primarily White (37.7%), then Hispanic (26.0%) or Asian (25.9%). Median age was 3.03 years old.

Prenatal cannabis use rose from 4.5% in January 2012 to 7.1% in January 2018. At the time of recreational cannabis use legalization in California, there was no change use rates among early-pregnancy women. In the first month after recreational cannabis implementation, the rate of prenatal cannabis use increased to 8.6% in February 2018—indicating a level change increased risk of 10% (RR, 1.10; 95% CI, 1.04 – 1.16). The team observed no difference in prenatal cannabis use based on toxicology test self-report.

Based on local policies, investigators observed that post-recreational cannabis legalization increase in use was only observed in jurisdictions that which allowed adult-use cannabis retailers (RR, 1.21; 95% CI, 1.10 – 1.33).

In prior research, another team of US investigators observed that public health interventions including warning sign policies do not seem to deter the rate of women who use cannabis during pregnancy.

In reviewing the findings, Young-Wolff and colleagues concluded that the implementation of legalized recreational cannabis in California was linked to an increase in early pregnancy cannabis use.

“Longer-term studies are needed to understand whether trends persist or change further

over time,” the team wrote. “As legalization spreads across the US, it will be important to test whether local policies that prohibit or limit adult-use retailers moderate changes in prenatal cannabis use associated with state-level legalization.”

References

1. ^{California Courts. Proposition 64: Legalizes Marijuana. Accessed October 30, 2024. Available from: https://www.courts.ca.gov/prop64.htm#:~:text=Effective%20November%209%2C%202016%2C%20Proposition,sealing%20of%20prior%2C%20eligible%20marijuana%2D}
2. ^{Krewson C. Impact of warning signs on cannabis use during pregnancy. Contemporary OB/GYN. Published June 21, 2023. https://www.contemporaryobgyn.net/view/impact-of-warning-signs-on-cannabis-use-during-pregnancy}