Female sleep patterns, shift work, and fecundability in a North American preconception cohort study

OBJECTIVE: To prospectively evaluate the association between female sleep patterns, shift work, and fecundability. DESIGN: Web-based preconception cohort study, Pregnancy Study Online (PRESTO). SETTING: Not applicable. PATIENT(S): North American Women aged 21-45 years attempting pregnancy. INTERVENTION(S): Not applicable. MAIN OUTCOME MEASURE(S): At baseline, self-reported average sleep duration per 24-hour period in the previous month, the frequency of trouble sleeping within the last 2 weeks (as measured by the Major Depression Inventory), and shift work patterns. Pregnancy status determined by follow-up questionnaires completed every 8 weeks for up to 12 months or until conception. RESULT(S): The analyses were restricted to 6,873 women attempting pregnancy for ≤6 months at enrollment from June 2013 through September 2018. We used proportional probabilities regression models to estimate fecundability ratios (FRs) and 95% confidence intervals (CIs), adjusting for potential confounders. Relative to 8 hours of sleep per day, FRs for 50% of the time were 0.93 (95% CI, 0.88-1.00) and 0.87 (95% CI, 0.79-0.95), respectively. The results were slightly stronger among women with higher depressive symptoms and perceived stress levels. There was no association between shift work and fecundability. CONCLUSION(S): Trouble sleeping at night was associated with modestly reduced fecundability. A weaker inverse association was observed between shorter sleep duration and fecundability.