Cannabis use in women before and during pregnancy increased in the past decade, with daily use increasing most rapidly, according to the results of a California-based cohort study.
Among women self-reporting using cannabis during pregnancy, the percentage using daily rose from 14.6% in 2009 to 20.9% in 2017, reported Kelly C. Young-Wolff, PhD, of Kaiser Permanente in Northern California in Oakland, writing in JAMA Network Open.
The study also found daily use in the year before pregnancy jumped from 17.15 to 25.25 as a proportion of cannabis users during the study period.
„These increases in daily use of cannabis during pregnancy are consistent with recent U.S. data,” Young-Wolff told MedPage Today via email.
Overall, pregnant women reported cannabis use during pregnancy at rates of 1.95% in 2009, rising to 3.38% in 2017, the study found.
Current research suggests that using cannabis during pregnancy may result in adverse fetal health outcomes. Some studies suggest it may be associated with lower birthweight and compromised neuropsychological functioning, Young-Wolff and colleagues wrote.
Despite these warnings, study authors said that the general acceptance and accessibility of marijuana has led to increased use among pregnant women.
In an accompanying editorial, Torri Metz, MD, MS, of the University of Utah Health in Salt Lake City and Elaine Stickrath, MD, of Denver Health and Hospital also wrote that it was no surprise that Young-Wolff and colleagues found increasing rates of cannabis use in reproductive-age women.
„The question is whether these data are a cause for alarm,” they wrote.
The American College of Obstetricians and Gynecologists' (ACOG) guidelines recommend women refrain from using marijuana during pregnancy, due to insufficient knowledge about the health effects it has on infants. While there is not enough information to fully assess the risks, previous studies have shown that a higher frequency in use may be tied to negative health outcomes, Metz and Stickrath said.
„Much of the existing literature concerning the associations of marijuana use with maternal and child outcomes is limited by a lack of quantification and timing of exposure,” the editorialists wrote. „Therefore, it remains difficult to evaluate how the frequency of use is associated with obstetrical outcomes.”
To better understand how frequency of use affects infants, Young-Wolff and colleagues examined daily, weekly, and monthly cannabis use in women both before and during pregnancy. No previous work has looked into frequency of use, they wrote.
This cross-sectional study used data from more than 367,000 pregnancies in almost 277,000 women ages 11 and older. The data comprises of self-reported questionnaires and urine toxicology tests from standard 8-week prenatal care drug screenings. All of the women in the study were patients in the Kaiser Permanente Northern California health system from 2009 to 2017.
Around 36% of women were white, 28% were Hispanic, 17% were Asian, and 6% were African American. Over 60% of women were ages 25-34. Median household income in the study population was $70,472. More than 75,000 (27%) of women had more than one pregnancy from 2009 through 2017.
More frequent cannabis use was associated with younger age, African-American women, and lower median household income. But the authors added that annual relative rate increases among daily, weekly, and monthly use of cannabis in the year before and during pregnancy were consistent among race and ethnicity groups, age, and median household income, which led them to believe that increases in the frequency of cannabis use are consistent across these sub-groups.
In the year before pregnancy, adjusted prevalence of self-reported cannabis use increased from 6.8% in 2009 to 12.5% in 2017. It rose from 1.95% to 3.38%, respectively, during pregnancy. Daily use rose from 1.17% to 3.05% in the year before pregnancy, and from 0.28% to 0.69% during pregnancy.
This study had several limitations. Firstly, the study was based on prenatal exams in patients from Kaiser Permanente Northern California, and may not be applicable to women outside of that healthcare system or without access to healthcare. Data was also obtained from an 8-week gestation prenatal exam, and does not account for continued drug use that may have occurred. Finally, prenatal cannabis use was self-reported, which may lead to underestimates.
Metz and Stickrath agreed with the study authors that despite a lack of sufficient knowledge, there is a need for more conversation about the possible harms of cannabis use during pregnancy with patients.
„As clinicians, we must remind reproductive-aged women that there are no known benefits of marijuana use in pregnancy and that there are associated harms,” they wrote.
This study was supported in part by the NIH.
Young-Wolff and colleagues received grants from the National Institutes of Health (NIH) National Institute on Drug Abuse (NIDA) during the conduct of the study.