Researchers say an increase in emergency room visits and hospitalizations related to cannabis use by pregnant women is raising concerns about risks including preterm labour, low birth weight and negative effects on the baby's developing brain.
Their study was based on data from 980,398 pregnancies in Ontario among 691,242 people between January 2015 and July 2021. Of those, 540 individuals visited an ER or were hospitalized for cannabis use.
The rate of ER and hospital visits related to cannabis use during pregnancy increased to 20 per 100,000 pregnancies, up from 11 per 100,000 since legalization.The study found some patients were intoxicated or "very high" when they sought care, the lead researcher said.
Dr. Daniel Myran, a family physician and addiction specialist, said while the absolute increase in ER visits and hospitalizations was low, many more people may be using cannabis during pregnancy and not ending up in hospital.
"If that's the case, I think it has important implications for the health of children who will be born from these pregnancies," said Myran, a fellow at the Bruyère Research Institute and The Ottawa Hospital.
Some of the patients had a cannabis use disorder and were unable to stop using, while about 22 per cent experienced withdrawal, he said.
"This is not someone who used cannabis once or twice during pregnancy," said Myran, also a post-doctoral trainee at ICES, formerly known as the Institute for Clinical Evaluative Sciences.
The study, which also involved Unity Health Toronto, was published Tuesday in the Canadian Medical Association Journal (CMAJ).
The study suggested some may have used cannabis to relieve symptoms of morning sickness.
Montreal resident Jordana Zabitsky said that when she was expecting her second child, she knew exactly how to quell the morning sickness that made her miserable — by smoking more cannabis than during her first pregnancy.
Zabitsky started using cannabis for depression, anxiety and PTSD about two years before the birth of her son in 2016, when she ditched prescription drugs because of their side-effects.
During her first pregnancy, she limited her cannabis use because she worried about whether it could affect her baby.
"I would take about four puffs of a joint once or twice a week," Zabitsky said.
Her son weighed seven pounds, six ounces when bornat full term and reached all of his milestones, so she decided to use cannabis regularly during her second pregnancy.
"I used it as needed. I didn't track how much I was using. I just woke up and I would use it because it would prevent me from throwing up in the morning. It helped give me an appetite."
Her daughter was born in 2017 weighing six pounds, 13 ounces and her obstetrician was aware of her cannabis use, said Zabitsky, who co-founded a group called Mothers Mary to support others wanting to try the substance during pregnancy.
During both pregnancies, she said cannabis also helped ease pelvic pain that made it difficult for her to walk.
"It's not like we're sitting around being like, 'Oh, let's smoke a joint to get high. You're sitting there thinking, I really want to get better. I don't want to feel depressed anymore."
Dr. Darine El-Chaar, a maternal fetal medicine specialist at The Ottawa Hospital and another study co-author, said some of her patients believe the legalization of recreational cannabis means it's not so risky during pregnancy — but that's not the case.
Multiple studies have shown cannabis use during pregnancy is associated with increased risk of early delivery, low birth weight,along with autism and attention deficit hyperactivity disorder (ADHD), El-Chaar said.
The study considered low birth weight for babies born at full term to be less than 5.5 pounds.
Pregnant people, especially those with a history of substance use, mental health conditions and severe morning sickness, would benefit from regular screening by an obstetrician without stigma, she said.
"We show that the patients who presented with acute care for cannabis had a higher rate of (morning sickness). But we don't know for sure if that's pregnancy related or related to cannabis use."
She said common prescription drugs for morning sickness have been well studied over time and anyone experiencing nauseaor other symptoms during pregnancy should see a health-care provider before considering cannabis.
"I hear all the time from patients that 'I did it with my other pregnancy. it's a natural substance. And I often say that it's not all pregnancies where (babies) are exposed to alcohol, cigarettes or cannabis that they're going to have negative outcomes. But the proportion of negative outcomes is higher compared to non-use."
The data did not show a rise in acute care visits for use of other substances, including alcohol and opioids, El-Chaar noted.
The Society of Obstetricians and Gynaecologists of Canada says there is strong evidence that cannabis use during pregnancy poses risk of lifelong harm to a developing fetus related to memory function, hyperactive behaviour, anxiety and depression.
This report by The Canadian Press was first published May 23, 2023.
Canadian Press health coverage receives support through a partnership with the Canadian Medical Association. CP is solely responsible for this content.
Camille Bains, The Canadian Press