In one of the largest studies of its kind, researchers from The Ottawa Hospital, BORN Ontario, and the University of Ottawa found “an association between maternal cannabis use in pregnancy and the incidence of autism spectrum disorder in the offspring” and “the incidence of intellectual disability and learning disorders was higher among offspring of mothers who use cannabis in pregnancy, although less statistically robust.”
The incidence of autism was 4 per 1000 among children exposed to cannabis in pregnancy, compared to only 2.42 among unexposed children. The findings were published in the prestigious medical journal, Nature Medicine.
Recreational cannabis is now legal for adults in Canada, eleven US states, and the District of Columbia. “Problematic use of marijuana among adolescents and adults increased after legalization of recreational marijuana use,” according to a 2019 study from NYU Grossman School of Medicine and Columbia University Mailman School of Public Health.
Americans and Canadians increasingly believe that using cannabis is without significant risks but addiction professionals warn that it can lead to a substance use disorder. A 2016 study conducted by the National Institute on Alcohol Abuse and Alcoholism (NIAAA) concluded that “marijuana use disorder is common and often untreated.”
“Marijuana use during pregnancy can be harmful to your baby’s health,” according to the Centers for Disease Control and Prevention (CDC). “The chemicals in marijuana (in particular, tetrahydrocannabinol or THC) pass through your system to your baby and can harm your baby’s development.” Health Canada and the Society of Obstetricians and Gynaecologists of Canada also recommend against pregnant or breastfeeding women using cannabis. Health warnings to this effect appear on cannabis packaging. Given the potential of marijuana negatively affecting the developing brain, the American College of Obstetricians and Gynecologists recommends that obstetric and gynecology physicians counsel women against using marijuana while trying to get pregnant, during pregnancy, and while they are breastfeeding.
“Despite these warnings, there is evidence that more people are using cannabis during pregnancy,” said Dr. Mark Walker, Chief of the Department of Obstetrics, Gynecology and Newborn Care at The Ottawa Hospital and senior author on the study. “This is concerning because we know so little about how cannabis affects pregnant women and their babies. Parents-to-be should inform themselves of the possible risks, and we hope studies like ours can help.”
As cannabis becomes more socially acceptable, many healthcare researchers are concerned that some pregnant women may consider using marijuana to treat morning sickness.
“In the past, we haven’t had good data on the effect of cannabis on pregnancies,” said Dr. Daniel Corsi, Epidemiologist at The Ottawa Hospital and BORN Ontario. “This is one of the largest studies on this topic to date. We hope our findings will help women and their healthcare providers make informed decisions.”