Men's Marijuana Use Linked to Elevated Miscarriage Risk

Megan Brooks

November 25, 2019

PHILADELPHIA — The use of marijuana by a man can affect the success of his partner's pregnancy, according to new research.

"Some studies have shown that marijuana may negatively affect sperm quality and increase DNA fragmentation, which may contribute to adverse pregnancy outcomes, including miscarriage, so there is a plausible mechanism," said Alyssa Harlow, a doctoral student at the Boston University School of Public Health.

"To our knowledge, this is the first study that's looked at observational research that followed couples forward through time and looked at male marijuana use during the preconception period and miscarriage," Harlow told Medscape Medical News.

She reported findings from an analysis of data from the Pregnancy Study Online (PRESTO) study, a North American preconception cohort study of couples planning to start a family, here at the American Society for Reproductive Medicine 2019 Scientific Congress.

At study enrolment, the men and women separately reported demographic characteristics, medical history, and lifestyle and behavioral factors, including marijuana use. In addition, women completed bimonthly follow-up surveys until conception and at various stages during pregnancy.

In the 1535 couples followed, 1267 (82.5%) men reported no marijuana use in the 2 months before study enrolment, 140 (9.1%) reported marijuana use less than once a week, and 128 (8.3%) reported marijuana use at least once a week.

During follow-up, 292 (17.5%) women experienced a spontaneous abortion.

The risk for spontaneous abortion was nearly twofold higher when expectant fathers used marijuana at least once a week than when they did not use marijuana. There was no increased risk when fathers used marijuana less than once a week.

Table. Male Marijuana Use and Risk for Spontaneous Abortion
Frequency of Use Adjusted Hazard Ratio 95% Confidence Interval
Less than once weekly 1.06 0.65–1.72
At least once weekly 1.99 1.26–3.14

The elevated risk persisted when the analysis was restricted to couples in which the woman did not use marijuana (hazard ratio [HR], 1.95; 95% confidence interval [CI], 1.13 - 3.37). And the association between a man's weekly marijuana use and pregnancy loss before 8 weeks became slightly stronger (HR, 2.29; 95% CI, 1.32 - 3.99), which "gives us confidence" to say that marijuana use might damage sperm, Harlow told Medscape Medical News.

"There have long been concerns about the impact of marijuana on sperm quality. As the legal landscape changes, it is important that we do more of this kind of research to help us counsel our patients," Harris Nagler, MD, president of the Society for Male Reproduction and Urology, said in a statement.

Concerning Finding

"This finding is concerning," said Eve Feinberg, MD, from Northwestern Medicine in Chicago, who is vice president of the Society for Reproductive Endocrinology and Infertility. "As marijuana is becoming legalized, its use is much more ubiquitous. I think people assume legal equals safe, but that's certainly not the case."

"I generally tell patients that we don't have a lot of good data, but my gut feeling is that it's probably not good for you," she told Medscape Medical News. "I tell couples to abstain in the same way that I tell them not to smoke cigarettes and that an occasional alcoholic beverage is okay, but we just don't know, and cleaner is probably better."

American Society for Reproductive Medicine (ASRM) 2019 Scientific Congress: Abstract O-4. Presented October 14, 2019.

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