Rise in marijuana use among pregnant women linked to premature births

By Melissa Malamut

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As cannabis use continues to become more and more mainstream, medical science is (finally) ramping up research to see how the still-illegal-in-New York drug affects fertility and reproduction.

And, unsurprisingly, it turns out bongs and babies do not mix.

“Our research team has been focusing on substance use in pregnancy, and the potential effects on the unborn child, which also may affect them in later life,” the study’s senior author, Dr. Mark Walker, the head of the department of obstetrics, gynecology and newborn care at Ottawa Hospital, tells the Post.

Walker and his team published a new study this month in the Journal of the American Medical Association that found women who reported marijuana use during their pregnancy had a consistently elevated risk of preterm birth and “small for gestational age” babies. Researchers used the BORN Ontario perinatal registry, which collects data on every pregnancy and birth in the province.

“We used a new approach which matched women who reported use with those who did not use cannabis,” Walker says. “The matching accounts for other factors, including tobacco smoking and alcohol, which may also lead to adverse outcomes such as preterm birth.”

In the study, the overall rate of preterm birth was 12% in reported users compared to 6% in non-users.
While twice the risk seems like an important stat, Walker says the numbers were slightly lower after accounting for other factors like the age of the mother, obstetrical history, and the use of other drugs and alcohol in pregnancy. After taking this into account, the rates were 10% vs 7% (so 3% percent higher or about 1.4 times the rate).

“Cannabinoids can readily cross the placenta and enter the fetal bloodstream,” Walker says.

“These compounds can disrupt fetal development and may have lasting effects on the child.”

Some of the adverse outcomes Walker notes are related to “reduced fetal growth and development,” which can lead to a baby being born smaller in size than average. There is also the added risk of prematurity in the children and a host of other medical problems that may require neonatal intensive care, he says.

But, fortunately, not all the blame can be placed on women. Researchers at Duke University recently found that cannabis use in men of reproductive age can alter DNA in sperm, including methylation, a process essential to normal development.

“What we have found is that the effects of cannabis use on males and their reproductive health are not completely null, in that there’s something about cannabis use that affects the genetic profile in sperm,” said Scott Kollins, Ph.D., professor in psychiatry and behavioral sciences at Duke said in a statement.

Still, more studies are in the works. Walker and the Ottawa researchers are planning additional research using the BORN Ontario perinatal registry, which now has more than 1 million births recorded.