VANCOUVER — Men and women who smoke marijuana could be adding to their infertility woes if they are already struggling to start a family, says an obstetrician-gynecologist who is calling for more research into reproductive aspects of the recreational drug that may be increasingly used in Canada since it was legalized.
Dr. Sara Ilnitsky, who practises at a fertility clinic in London, Ont., said some studies suggest that changes in ovulation patterns and reduced sperm motility are associated with smoking cannabis and could compound the frustrations of a couple trying to conceive.
Ilnitsky and coauthor Dr. Stan Van Uum, an endocrinologist in the same city, have outlined key points about marijuana and fertility in Monday’s publication of the Canadian Medical Association Journal.
THC, the active ingredient in marijuana, acts on the body’s endocannabinoid system, which is part of the reproductive tissues of both men and women, Ilnitsky said. She adds, however, that research suggesting the drug may delay or inhibit ovulation and lower sperm counts is limited and based on self-reported use of the drug that is taken at varying doses.
A direct measure of the effects of smoking pot is possible with men by testing their semen quality, but it’s “extraordinarily difficult” to gauge the potential impact on women, she said.
“Our best evidence will probably come from men and the best way to look at it would be to look at a cohort of men who have been smoking marijuana at a fairly predictable frequency so we know how much they’re getting and how often, which is hard to know because there’s different concentrations and different strains,” she said.
The largest clinical study, reported in the American Journal of Epidemiology in 2015, recruited about 1,200 Danish men between the ages 18 and 25, who provided semen samples and answered a questionnaire about their lifestyle and use of marijuana and other recreational drugs.
A total of 45 per cent of them reported they had smoked pot within the last three months, according to the study that found a 28 per cent reduction in sperm concentration in those who used the drug more than once a week.
A 2007 study in the Journal of Women’s Health involving 201 participants suggested ovulation was delayed by two days for frequent marijuana smokers versus 3.5 days for women who did not use the drug frequently, a finding Ilnitsky called interesting but counterintuitive.
However, it’s not possible to know from such studies whether other lifestyle factors, including cigarette smoking, alcohol and diet may also play a role when it comes to infertility. But couples who are having difficulty conceiving should avoid using cannabis as they consider other lifestyle changes toward good health, she said.