The Impact of Physical Activity on Sleep during Pregnancy: A Secondary Analysis

Disturbed sleep is independently associated with adverse pregnancy outcomes. The primary aim of this research which tested Pender’s Model of Health Promotion was to evaluate the contribution of physical activity (PA) to sleep parameters in pregnant women, with pre-pregnant body mass index (BMI) as a confounder. Sleep and physical activity data were drawn from a parent study in which 29 sedentary women in the second trimester were enrolled in an 8-week PA intervention pilot study and randomly assigned to intervention or control group. Steps per day, as measured by pedometer, and sleep parameters (sleep onset latency [SOL], wake time after sleep onset [WASO], sleep duration, and sleep quality), obtained from sleep diaries, were used to evaluate the daily interaction between PA levels and sleep. Hierarchical linear modelling (HLM) was used for analysis, as data were nested within persons. Pre-pregnant BMI contributed negatively to PA levels (p=0.003). PA levels were positively predictive (p=0.037) of sleep onset latency (SOL) and negatively predictive (p=0.01) of sleep quality, demonstrating a negative effect of PA on sleep during pregnancy when measured daily. These results confirm results from the only other published study that looked at daily measures, but contradict findings from other studies that evaluated the PA level-sleep relationship over a week or month. Both PA and sleep are modifiable factors that affect pregnancy outcomes. Further studies are needed to understand the complex relationship between PA, sleep, and weight in pregnancy.