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 <6, 6, 7, and ≥9 hours of sleep/day were 0.89 (95% CI, 0.75-1.06), 0.95 (95% CI, 0.86-1.04), 0.99 (95% CI, 0.92-1.06), and 0.96 (95% CI, 0.84-1.10), respectively. Compared with no trouble sleeping, FRs for trouble sleeping <50% of the time or trouble sleeping >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.