An observational study of pregnant women in Northern California suggests marijuana use before and during pregnancy has increased over time.
The study of nearly 277,000 women in Kaiser Permanente Northern California included 367,403 pregnancies from 2009 to 2017. The women reported marijuana use on questionnaires as part of standard prenatal care. The authors report marijuana use in the year before pregnancy increased from 6.8% of women in 2009 to 12.5% in 2017, and marijuana use during pregnancy increased from 1.95% to 3.38%.
Daily use of marijuana in the year before pregnancy increased from 1.17% in 2009 to 3.05% in 2017, and daily use during pregnancy increased from 0.28% to 0.69%. A limitation of the study is that the results may not be generalizable to women outside of California or those without access to health care.
Young-Wolff, C K. et al. (2019) Self-reported Daily, Weekly, and Monthly Cannabis Use Among Women Before and During Pregnancy. JAMA Network Open. doi.org/10.1001/jamanetworkopen.2019.6471