Ottawa, Ontario — Monday August 10, 2020
In the largest study of its kind, researchers from CHEO Research Institute, The Ottawa Hospital, BORN Ontario and the University of Ottawa found that children whose mothers reported using cannabis during pregnancy were at greater risk of autism. The incidence of autism was 4 per 1000 person-years among children exposed to cannabis in pregnancy, compared to 2.42 among unexposed children. The findings were published in the prestigious medical journal Nature Medicine.
“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, professor at the University of Ottawa 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.”
Considering those findings, in the current study the researchers specifically looked at 2,200 women who reported using only cannabis during pregnancy, and no other substances. They found that babies born to this group still had an increased risk of autism compared to those who did not use cannabis.
The researchers do not know how much cannabis the women were using, how often, at what time during their pregnancy, or how it was consumed. They also note that while they tried to control for other factors that could influence neurological development, their study can still only show association – not cause and effect.
“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, which is affiliated with the CHEO Research Institute. “This is one of the largest studies on this topic to date. We hope our findings will help women and their health-care providers make informed decisions.”
Women who are thinking about or currently using cannabis during pregnancy should talk to their health-care provider to help make an informed choice about what is best for them and their baby.