Rates of Prenatal Cannabis Use Among Pregnant Women Before and During the COVID-19 Pandemic

Cannabis use among pregnant women is common and has increased in recent years in the US, from an estimated 3.4% in 2002 to 7.0% in 2017.¹ Pregnant women report using cannabis to relieve stress and anxiety,² and prenatal cannabis use may have risen during the COVID-19 pandemic as pregnant women faced general and pregnancy-specific COVID-related stressors (eg, social isolation, financial and psychosocial distress, increased burden of childcare, changes in prenatal care, and concerns about heightened risks of COVID-19).^3,4

Considered an essential business in California, cannabis retailers remained open during the pandemic with record sales in 2020.⁵ We used data from Kaiser Permanente Northern California (KPNC), a large integrated health care delivery system with universal screening for prenatal cannabis use to test the hypothesis that rates of prenatal cannabis use increased during the COVID-19 pandemic.

The sample comprised all KPNC pregnant women screened for prenatal cannabis use via a universal urine toxicology test from January 1, 2019, through December 31, 2020, during standard prenatal care (at ≈8 weeks’ gestation). The institutional review board of KPNC approved this study and waived the need for informed consent.

We computed monthly rates of prenatal cannabis use standardized to the year 2020 age and race and ethnicity distribution. We fit interrupted time-series (ITS) models to monthly rate data using negative binomial regression, adjusted for age (<25, 25 to <35, ≥35 years) and self-reported race and ethnicity (Asian/Pacific Islander, Black, Hispanic, non-Hispanic White, or other or unknown), which were included because of the known age and race and ethnicity differences in the prevalence of prenatal cannabis use. The prepandemic period was defined as urine toxicology tests conducted from January 2019 to March 2020 and the pandemic period from April through December 2020 (see Laboratory Methods in the Supplement).

The rate ratio and corresponding 95% CIs are reported herein. We conducted the analyses using SAS version 9.4 (SAS Institute Inc). A 2-sided P < .05 was considered statistically significant.

Of 100 005 pregnancies (95 412 women), 26% were Asian or Pacific Islander; 7%, Black; 28%, Hispanic; 34%, non-Hispanic White; and 5%, other, unknown, or multiracial. The patients were a mean age of 31 years (median, 31 years). There were negligible differences in age or race and ethnicity in the 2 periods. During the pandemic, patients completed toxicology testing slightly earlier in their pregnancies (before pandemic mean, 8.51 weeks’ gestation; during pandemic mean, 8.04 weeks’ gestation).

Before the pandemic, the standardized rate of prenatal cannabis use was 6.75% of pregnancies (95% CI, 6.55%-6.95%); that rate increased to 8.14% of pregnancies (95% CI, 7.85%-8.43%) during the pandemic (Figure). In the ITS analysis, we found that prenatal cannabis use increased by 25% (95% CI, 12%-40%; Table) during the pandemic over prenatal cannabis use during the 15 months before the pandemic. The ITS analysis confirmed that these rates before and during the pandemic were stable, with no statistically significant month-to-month trends (Table).

Rates of biochemically verified prenatal cannabis use increased significantly during the COVID-19 pandemic among pregnant women in Northern California. Results are consistent with the rise in cannabis sales seen in California during the same period.⁵ When the toll of the COVID-19 pandemic begins to fade and restrictions are lifted, it is unknown whether pandemic-related increases in rates of cannabis use during pregnancy will reverse or remain elevated. Continued monitoring of trends is critical as the pandemic continues to evolve.

This study is limited to pregnant women universally screened in the KPNC system for prenatal cannabis use via urine toxicology testing early in pregnancy (≈8 weeks’ gestation) as part of standard prenatal care, and data do not reflect continued use throughout pregnancy. In some cases, positive toxicology test results may detect prenatal cannabis use that occurred prior to pregnancy recognition. Additional studies that capture pandemic-related changes in frequency of and reasons for cannabis use during pregnancy and among nonpregnant women are also needed.

Prenatal cannabis use is associated with health risks, including low infant birth weight and potential effects on offspring neurodevelopment.⁶ Clinicians should educate pregnant women about the harms of prenatal cannabis use, support women to quit, and provide resources for stress reduction.

Accepted for Publication: September 9, 2021.

Published Online: September 27, 2021. doi:10.1001/jama.2021.16328

Corresponding Author: Kelly C. Young-Wolff, PhD, MPH, Division of Research, Kaiser Permanente Northern California, 2000 Broadway, Oakland, CA 94612 (kelly.c.young-wolff@kp.org).

Author Contributions: Dr Young-Wolff had full access to all of the data in the study and takes responsibility for the integrity of the data and the accuracy of the data analysis.

Concept and design: Young-Wolff, Alexeeff, Adams, Does, Ansley, Avalos.

Acquisition, analysis, or interpretation of data: Young-Wolff, Ray, Alexeeff, Adams, Ansley, Avalos.

Drafting of the manuscript: Young-Wolff, Ray.

Critical revision of the manuscript for important intellectual content: All authors.

Statistical analysis: Ray, Alexeeff, Avalos.

Obtained funding: Young-Wolff, Avalos.

Administrative, technical, or material support: Young-Wolff, Adams, Does, Ansley, Avalos.

Supervision: Young-Wolff, Avalos.

Conflict of Interest Disclosures: None reported.

Funding/Support: This study was supported by grants DA047405, DA043604, and DA048033 from the National Institute on Drug Abuse.

Role of the Funder/Sponsor: The National Institute on Drug Abuse had no role in the design and conduct of the study; collection, management, analysis, and interpretation of the data; preparation, review, or approval of the manuscript; and decision to submit the manuscript for publication.