November 16, 2023 (Toronto) – A meta-analysis of studies published over the past 40 years on cannabis use during pregnancy has found an association between fetal exposure to cannabis in the womb and preterm delivery, low birth weight and the need for neonatal intensive care admission (NICU).
The study, Birth, Cognitive and Behavioural Effects of Intrauterine Cannabis Exposure in Infants and Children: A Systemic Review and Meta-Analysis, was published today in the journal Addiction.
Previous research has indicated that THC, the main psychoactive component in cannabis, can cross the placenta to the fetus during pregnancy and bind to receptors in the fetal brain.
The meta-analysis examined the results of 57 studies around the world that included almost 13 million infants in total. Based on either self-reports from pregnant women, or blood and saliva testing depending on the study, just over 100,000 infants were found to be exposed to cannabis in the womb. While none of the studies found a direct causal relationship between cannabis use during pregnancy and adverse birth outcomes, the combined results indicated that newborns exposed to cannabis during pregnancy were twice as likely to require NICU admission, twice as likely to have a low birth rate and one and a half times more likely to be born early.
While there has been little research on cannabis use during pregnancy since cannabis was legalized in Canada five years ago, an American study has indicated an increase in cannabis use during pregnancy in states where it has been legalized and the perceived risk of harm from cannabis has decreased. The study states that overall cannabis use in pregnancy has doubled in the past 20 years, with approximately 10 per cent of pregnancies associated with cannabis exposure. Some studies indicated it was being used to alleviate symptoms of nausea, poor appetite, insomnia or anxiety during pregnancy.
Canada’s Lower Risk Cannabis Use Guidelines , developed by a nationwide team led by CAMH scientists, recommends cannabis abstinence during pregnancy.
“This research emphasizes the importance of healthcare providers making an effort to create a safe space talking to pregnant women and women planning to be pregnant about their cannabis use and their motivations for using it to educate them about the potential risks and empower them to make informed decisions for their child,” says lead author Maryam Sorkhou, a PHD student within the addictions division at CAMH as well as the University of Toronto. Ms. Sorkhou is overseen at CAMH by Senior Scientist and paper co-author Dr. Tony George.
Funding for the study was provided by the CAMH Discovery Fund.
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