Table 1.

Sleep variable definitions

Variable name	Variable description
Sleep duration (hours)	Sleep duration was defined as the total amount of time scored as sleep during the main designated rest period each day. The sleep duration for each available day (5–7 days) were then averaged. The cut off of an average sleep duration of < 7 hours was chosen based on prior data in pregnant women from the authors and on recommendations for adequate sleep duration recently published by the American Academy of Sleep Medicine.
Sleep midpoint (hh:mm)	Sleep midpoint is the clock time that represents the midpoint between the clock time of sleep onset and the clock time of sleep offset. The sleep midpoint was calculated for each valid day then averaged for each available day (5–7 days). The cut off of an average sleep midpoint later than 5am was chosen a priori based on large samples of population based self-reported data.
Wake after sleep onset (minutes)	Wake after sleep onset (WASO) is the total amount of minutes spent awake between sleep onset and the end of the rest interval. The minutes of WASO were calculated for each valid day then averaged for each available day (5–7 days). Given that there are no well-established actigraphy based cutoffs for WASO, the data were divided into quartiles and those with an average WASO ≥ 75th percentile were considered to have poor sleep.
Sleep fragmentation (%)	The sleep fragmentation index (FI) is calculated as the proportion of all epochs from sleep onset to sleep offset with an activity count of 2 or greater plus the proportion of all bouts of immobility (activity count less than 2 in every epoch) that were 1 minute or less in duration. The FI was determined for each valid day then averaged for each available day (5–7 days). Given that there are no well-established actigraphy based cutoffs for FI, the data were divided into quartiles and those with an average FI ≥ 75th percentile were considered to have poor sleep.