Expecting mothers’ marijuana use during pregnancy has been long debated, especially as cannabis legalization becomes more widespread. Now, in a new study, researchers found that using marijuana while pregnant may increase the risk that their child will develop autism.
“Women who used cannabis during pregnancy were 1.5 times likely to have a child with autism,” stated study author Dr. Darine El-Chaâr, a maternal-fetal medicine specialist and clinical investigator at Ottawa Hospital Research Institute in Canada.
The study did not include the amount and type of marijuana the women used during pregnancy, nor when or how frequently the women used it. With new links to autism in mind, El-Chaâr “highly” discourages cannabis use during pregnancy and breastfeeding.
The latest study reviewed data from every birth in Ontario, Canada between 2007 and 2012, before recreational use was legalized in Canada in 2017. Out of the half a million women in the data pool, the study narrowed down 2,200 women who claimed to only use marijuana during pregnancy, without mixing it with alcohol, tobacco, or opioids.
Linking Marijuana Use and Pregnancy Risks

According to the Centers for Disease Control and Prevention (CDC), marijuana use was linked to low birth weight, attention issues, impulsivity, hyperactivity, and other behavioral and cognitive issues in children. CNN reports that another study found marijuana use caused a 2.3 times greater risk of stillbirth.
Last year, a study found that more moms-to-be were using marijuana than in previous years. The number of surveyed women admitting to marijuana use during pregnancy rose to 7% in 2016-2017. In the 2002-2003 research period, only 3% of women admitted to marijuana use during pregnancy. In the US, the CDC reports that 1 in 20 women report marijuana use during pregnancy.
Even as marijuana becomes legalized and discussed more openly, experts remain wary about its use during pregnancy. Any form of marijuana’s impact on fetal development — eating, drinking, topical substances, smoking — lacks intensive research. Currently, the CDC recommends that pregnant women or those breastfeeding their children do not use marijuana.
Autism Pregnancy Marijuana Use — Sources
CNN: Marijuana use during pregnancy linked to autism in babies, study says
NBC: Using marijuana in pregnancy may heighten baby’s risk of autism
CDC: What you need to know about marijuana use and pregnancy