Cannabis use during pregnancy has the ability to cause women to experience a premature birth and have higher rates of potentially serious complications – explore more about the pregnancy risk.
12% of babies whose mothers used drugs were born before 37 weeks, compared to 6% who did not, according to the study conducted in Canada. Fears increasing liberalisation of cannabis use around the world could expose more women to pregnancy risk.
Details of the study
The study used responses from more than 661,000 pregnancies in Ontario, Canada, including nearly 10,000 where the mother said they used cannabis.
Here, the study showed pregnant women had higher rates of placental abruption, a rare but serious complication where the placenta that supplies oxygen and nutrients to the foetus separates from the uterus.
It can cause heavy bleeding and pregnancy loss, and rates were 66% higher among women who said they used cannabis – affecting 1.6% of pregnancies compared to 0.9% in non-cannabis users.
Babies whose mothers used cannabis were also more likely to need intensive care (19.3% of pregnancies vs 13.8%) and be born with a low birth weight.“Cannabinoids can readily cross the placenta and enter the foetal bloodstream,” the authors said.
“Animal studies suggest that THC exposure during pregnancy can disrupt the complex foetal endogenous cannabinoid signalling system and may be associated with adverse pregnancy outcomes.”
Other factors may affect pregnancy risk
Published in the Journal of the American Medical Association, the study could not rule out that other factors common to women who use cannabis might be causing the effect.
The researchers did not say whether the way the drug was consumed affected the results.
The study was conducted as a part of an increasing trend of cannabis liberalisation around the world, with several US states adopting recreational use and the UK allowing medicinal cannabis on prescription.