Does frequent male marijuana use affect pregnancy?

A new study suggests that men who plan to father a child with their partner should reconsider their marijuana use. Men who frequently use cannabis are twice as likely to have their partner’s pregnancy end in miscarriage, according to a new data-driven study.

When studying miscarriages associated with regular marijuana use, researchers found that miscarriages typically occurred within eight weeks of conception, US News & World Report first reported.

Other studies have shown that frequent marijuana use reduces sperm count and motility in men. Alyssa Harlow, a graduate student at Boston University and lead author of the study, suggested that her team’s research could show how marijuana affects sperm DNA in fundamental ways.

“We assume the sperm is healthy enough to fertilize an egg, but any damage to the sperm could result in early pregnancy loss,” Harlow said.

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The research collected data from 1,400 couples in the United States and Canada, all of whom were planning to become pregnant. Only 8% of men reported using marijuana at least once a week, while 82% of men reported never using cannabis. About 19% of couples who actually became pregnant ultimately reported a miscarriage. If a man used marijuana weekly, the couple’s chances of miscarriage doubled.

Photo courtesy of Cannaclusive/Flickr

Participants in the study were not randomly assigned to cannabis use, nor did the researchers conduct a double-blind procedure. Instead, Harlow and her team controlled for as many influencing factors as possible, including weight, sleep patterns, alcohol consumption, smoking status, caffeine consumption, mood disorders and history of sexually transmitted infections. This limitation in the study meant that researchers only reported a link between male marijuana use and miscarriages and further studies are needed before a true cause-and-effect relationship can be proven.

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The study was presented during the annual meeting of the American Society of Reproductive Medicine. Research findings that have not been published in a peer-reviewed journal are considered preliminary, but the study is consistent with new scientific literature that is leading doctors to recommend men avoid marijuana use while trying to conceive.

Previous research from Denmark found that men’s reproductive organs have a robust endocannabinoid system, which was previously unknown, and showed how cannabis use affects sperm. Duke scientists also focused on what specific mutations sperm undergo when men regularly use marijuana. By combining experiments on rats and small humans, researchers discovered changes in a gene strongly linked to post-traumatic stress disorder, schizophrenia and autism. However, the Duke scientists expressed caution before drawing conclusions from their study.