Background: Male marijuana use has increased steadily over the last decade, but its effect on risk of spontaneous abortion to our knowledge has not been studied.
Results: Among 1535 couples who conceived during follow-up, 9% of men reported preconceptional marijuana use <1 time/week and 8% ≥1 time/week. Nineteen percent of pregnancies ended in spontaneous abortion. Compared with no use, adjusted hazard ratios (HRs) for male marijuana use were 1.1 (95% confidence interval [CI] = 0.64, 1.7) for <1 time/week and 2.0 (95% CI = 1.2, 3.1) for ≥1 time/week. The association for ≥1 time/week persisted after restricting to couples where the female partner did not use marijuana (HR = 2.0, 95% CI = 1.1, 3.3), and was stronger for losses at <8 weeks' gestation (HR = 2.5, 95% CI = 1.4, 4.3) and among males aged ≥35 years (HR = 4.1, 95% CI = 1.54, 11).
Conclusions: Couples with male partners who used marijuana ≥1 time/week during preconception had greater risk of spontaneous abortion than couples with males who did not use marijuana.