Insights into maternal sleep: a large-scale longitudinal analysis of real-world wearable device data before, during, and after pregnancy

Background Current understanding of pregnancy and postpartum sleep is driven by limited lab or self-reported data. Our goal is to use consumer wearable devices through an observational study to reveal longitudinal, real-world sleep patterns in this population. Methods We analysed retrospective, de-identified Fitbit device data from 2540 users in the United States and Canada who met strict wear-time requirements (>= 80% daily usage for >= 80% of the time periods of interest [12 weeks prepregnancy, throughout pregnancy, and 20 weeks immediately postpartum]). We tracked sleep time and stages using Fitbit devices. Findings Pregnant participants experienced a peak in total sleep time (TST) at 10 weeks (447.6 +/- 47.6 min), exceeding their prepregnancy average (425.3 +/- 43.5 min) before declining throughout pregnancy. This initial TST increase, mirrored by time in bed (TIB), was driven by more light sleep. Deep and rapid-eye movement sleep decreased significantly throughout pregnancy, with maximum reductions of 19.2 +/- 13.8 min and 9.0 +/- 19.2 min respectively by pregnancy end (two-sided t-test, p < 0.001 for both). Sleep efficiency also slightly declined during pregnancy (median drop: 88.3%-86.8%). Postpartum, TIB remained below prepregnancy levels by 14.7 +/- 45.7 min one year after birth and 15.2 +/- 47.7 min at 1.5 years after birth. Interpretation This study revealed a previously unquantified initial increase in sleep followed by decreases in both quantity and quality as pregnancy progresses. Sleep deficits persist for at least 1.5 years postpartum. These quantified trends can assist clinicians and patients in understanding what to expect through their pregnancy and postpartum journey.