RT Journal Article SR Electronic T1 Marijuana use and fecundability in a North American preconception cohort study JF Journal of Epidemiology and Community Health JO J Epidemiol Community Health FD BMJ Publishing Group Ltd SP 208 OP 215 DO 10.1136/jech-2017-209755 VO 72 IS 3 A1 Lauren A Wise A1 Amelia K Wesselink A1 Elizabeth E Hatch A1 Kenneth J Rothman A1 Ellen M Mikkelsen A1 Henrik Toft Sørensen A1 Shruthi Mahalingaiah YR 2018 UL http://jech.bmj.com/content/72/3/208.abstract AB 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.