Daily step-count and sleep metrics across pregnancy: an observational analysis of the LEAP cluster randomized...

We investigated daily associations between step count and sleep quality across trimesters using wearable devices.

Participants (N = 243; pre-pregnancy body mass index≥ 25 kg/m²) from a mobile health randomized clinical trial intervention arm, wore Fitbits day and night from ~8 weeks' gestation- delivery. Devices tracked daily step count (primary exposure), moderate to vigorous physical activity (MVPA) and light physical activity (LPA) (secondary exposures), and sleep measures (duration, stage length, efficiency, awakenings, midpoint and multidimensional sleep score). Covariate-adjusted mixed effects models estimated daily associations between movement and sleep outcomes, stratified by trimester.

Participants averaged 5795 steps/day. In trimester 1, step count (per 1000) was associated with shorter sleep duration (-23 min, odds ratio [OR] = 0.84, 95% confidence interval [CI] = -38.7 to -8.6). In the trimester 2, step count was associated with shorter sleep duration (-22 min, CI = -27.6 to -16.4), shorter light sleep (-10 min, CI = -13.3 to -6.6), longer deep (+4 min, CI = 2.7 to 6.1), and rapid eye movement (REM) sleep (+6 min, CI = 3.5 to 7.7). In trimester 3, step count was associated with lower odds of poor sleep (OR = 0.84, CI = 0.70 to 1.00), shorter light sleep (-14 min, CI = -18.4 to -9.3), longer deep (+6 min, CI = 3.3 to 7.8), and REM sleep (+8 min, CI = 5.5 to 11.4), and more awakenings (+0.9, CI = 0.4 to 1.4). Associations of MVPA and LPA with sleep were smaller in magnitude but relatively consistent with step count.

Higher daily step count was associated with higher quality sleep in the following night during second and third trimesters. These findings highlight step count as a potential target to support prenatal sleep quality.