Cannabis use in pregnancy has increased since 2012, new research published in the Canadian Journal of Public Health has found, a trend that is expected to continue now that recreational cannabis is legal across Canada.
Researchers at the Ottawa Hospital looked at data from the Better Outcomes Registry and Network (BORN) Ontario databasBe.
A total of 10,731 women reported using cannabis while pregnant, with 1.2 per cent of pregnant women reporting cannabis use in 2012 and 1.8 per cent reporting use in 2018.
“This study was conducted in Ontario but it can be generalized to other parts of Canada,” said Dr. Daniel Corsi, an epidemiologist at the Ottawa Hospital and the study’s co-author.
The majority of cannabis users in the study had a lower household income and were between the age of 15 and 24 years old.
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Research co-author Dr. Mark Walker, who is also the head of obstetrics at the Ottawa Hospital, said the findings are concerning.
“I think that the Society of Obstetricians and Gynaecologists, public health units and the government have been sending the messages out that no amount of marijuana exposure in pregnancy is safe, but I don’t think we can emphasize it enough.”
The Society of Obstetricians and Gynaecologists of Canada’s (SOGC) offers women the following advice on its website:
“There is not enough clinical evidence to accurately determine the beneﬁts or risks of using cannabis while pregnant. Until we have more definitive answers, not using cannabis during pregnancy is the safest option for you and your baby.”
Sam Kimura, a registered nurse who offers private in-home prenatal classes for expectant parents, said she is often asked about cannabis as a potential treatment for morning sickness.
“This has come up quite a few times on Facebook groups with moms suggesting that this is a natural medicine and because it’s legal now, they can use it for nausea during the first trimester and then also for use during labour to help with their labour pains.”
Kimura said she urges clients to speak to their doctors before using cannabis. Walker said moms-to-be need to be cautious of what they read online.
“There is a lot of lay literature on the web using cannabis for morning sickness and though it is a good anti-nauseate, it is not the medication we would recommend and in fact, we really feel that it is absolutely contraindicated.”
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A 2018 study published in The Journal of Pediatrics found prenatal cannabis use was associated with a 50 per cent increased likelihood of low birth weight. Author Tessa Crume said there is also evidence to suggest prenatal exposure could impact a child’s development later in life but she said at the moment, the research isn’t available.
“The biggest concern is that cannabis use in-utero would have an effect on fetal brain development and result in different brain structure or function as the child grows.”
Crume’s team is currently enrolling a cohort of pregnant who use cannabis once a week for a study that will look at the impact of cannabis exposure on fetal brain development.
The researchers plan to use neonatal brain imaging two weeks postpartum to determine if prenatal cannabis exposure has an effect of fetal brain structure.