Women who reported exposure to cannabis during pregnancy had higher rates of preterm birth compared to unexposed women, researchers found. Cannabis exposure in pregnant women in Canada was significantly associated with a higher risk of preterm birth (relative risk 1.41, 95% CI 1.36-1.47), reported Daniel J. Corsi, PhD, of Ottawa Hospital Research Institute in Canada, and colleagues. Compared with unexposed women, women exposed to cannabis were also associated with higher risks of other adverse outcomes, such as small for gestational age infants, placental abruption, and transfer to the neonatal ICU, they wrote in JAMA. The authors noted that prior clinical studies have found links between prenatal use of cannabis and stillbirth, lower birth weight, and small for gestational age infants, but that these studies have varied in methodology and "treatment of confounding factors." Researchers examined data from the Ontario Better Outcomes Registry & Network (BORN), specifically women ages ≥15 years, who delivered a singleton infant of at least 20 weeks gestation in an Ontario hospital from April 2012 to December 2017. Exposure to cannabis was recorded during routine prenatal care. Overall, there were about 667,000 women in the cohort, and 9,427 reported using cannabis. Mean age of mothers was around 30. The matched cohort was comprised of 5,639 records for cannabis users and around 98,500 records for non-users. Researchers found that rates of preterm birth in the matched cohort were 10.2% for women exposed to cannabis versus 7.2% among unexposed women. In addition, cannabis users were associated with significantly higher risks of adverse outcomes versus non-users, including: Small for gestational age infants: third percentile 6.1% vs 4.0% (RR 1.53, 95 % CI 1.45-1.61) Placental abruption: 1.6% vs 0.9% (RR 1.72, 95% CI 1.54-1.92) Transfer to neonatal ICU: 19.3% vs 13.8% (RR 1.40, 95% CI 1.36-1.44) 5-minute Apgar score <4: 1.1% vs 0.9% (RR 1.28, 95% CI 1.13-1.45) The authors also found a small, albeit statistically significant, protective association between cannabis use and preeclampsia (RR 0.90, 95% CI 0.86-0.95) and gestational diabetes (RR 0.91, 95% CI 0.86-0.96). Cannabis Use in U.S. Pregnant Women While Corsi and colleagues focused on data from Canada, a separate research letter in JAMA by Beth Han, MD, PhD, of the Substance Abuse and Mental Health Services Administration in Rockville, Maryland, and colleagues examined data from the U.S., and found that cannabis use among pregnant women increased from 2002 to 2017. They examined data from the National Survey on Drug Use and Health among women ages 12-44. They were asked about current pregnancy status, past-month cannabis use, and past-month number of days of use. Beginning in 2013, they were also asked if cannabis was recommended by healthcare professionals. Among about 467,000 respondents, adjusted prevalence of past-month cannabis use in pregnant women rose from 3.4% in 2002-2003 to 7.0% in 2016-2017. Past-month use was higher in the first trimester compared with the second and third trimesters, with an increase in first trimester use from 5.7% in 2002 to 12.1% in 2017. There were 0.5% of women who reported past-month cannabis use for "medical only purposes" from 2013 to 2017, the authors reported. Two Sides to the Debate In an accompanying editorial addressing both studies, Michael Silverstein, MD, of Boston University, and two colleagues said the findings "send a straightforward message that cannabis use in pregnancy is likely unsafe; with an increasing prevalence of use .... its potential for harm may represent a public health problem." But they also noted issues in the epidemiology used by Corsi and colleagues, stating that it "is no different from any other cohort study" and further limited by use of registry data. They also cited "historical context," specifically past debates about alcohol and cocaine during pregnancy, the latter of which led to the "racist social construct" of the "crack baby." The editorialists suggested that two "reasonable perspectives can be applied to the same body of literature and reach opposing, non-stigmatizing conclusions." For example, either a 41% increased relative risk of preterm birth is "unacceptably high" or that it may not be worth abstaining from a drug that could provide relief from morning sickness or increased relaxation based on a 2.98% absolute risk difference. Or, they added, it could be somewhere in the middle. "Perhaps [this data] represents part of an emerging story of an in utero substance exposure that is neither highly prevalent nor extremely rare, an outcome that is consequential more on a population than individual level, and an association between exposure and outcome that is moderate in both its magnitude and degree of certainty," Silverstein and colleagues wrote. "While an obvious reaction ... is that more research is necessary, more epidemiology is unlikely to completely resolve the complex issue of potentially safe moderate use or to completely remove the tendency to imbue data interpretation with implicit biases about groups of people," the editorialists noted. Source
