Abstract
BACKGROUND: The influence of marijuana use on human fertility has not been well studied. We evaluated the association between female and male use of marijuana and fecundability in Pregnancy Study Online, a prospective cohort of North American couples. METHODS: Female participants completed a baseline questionnaire on which they reported lifestyle and behavioural factors, including frequency of marijuana use within the previous 2 months. Male partners completed an optional baseline questionnaire on similar factors, including marijuana use. Women completed follow-up questionnaires every 8 weeks for 12 months or until pregnancy, initiation of fertility treatment or loss to follow-up, whichever came first. The analysis was restricted to 4194 women (1125 couples) with ≤6 cycles of pregnancy attempt time at study enrolment (2013-2017). Fecundability ratios (FR) and 95% CIs were estimated using proportional probabilities regression models, with adjustment for potential confounders. RESULTS: Men (14.2%) were more likely than women (11.6%) to be marijuana users. FRs for female marijuana use <1 and ≥1 time/week relative to non-use were 0.99 (95% CI 0.85 to 1.16) and 0.98 (95% CI 0.80 to 1.20), respectively. FRs for male marijuana use <1 and ≥1 time/week relative to non-use were 0.87 (95% CI 0.66 to 1.15) and 1.24 (95% CI 0.90 to 1.70), respectively. Associations for frequent marijuana use (≥1 time/week) were attenuated among non-smoking men (FR=1.21, 95% CI 0.84 to 1.74), but stronger among men reporting intercourse ≥4 times/week (FR=1.35, 95% CI 0.72 to 2.53). CONCLUSIONS: In this preconception cohort study, there was little overall association between female or male marijuana use and fecundability.