Accuracy of self-reported sleep position in late pregnancy

Abstract

Background: There is emerging research to suggest that supine maternal sleep position in late pregnancy may adversely affect fetal wellbeing. However, these studies have all been based on maternal report of sleeping position. Before recommendations to change sleep position can be made it is important to determine the validity of these studies by investigating how accurate pregnant women are in reporting their sleep position. If avoiding the supine sleeping position reduces risk of poor pregnancy outcome, it is also important to know how well women can comply with the instruction to avoid this position and sleep on their left.

Method: Thirty women in late pregnancy participated in a three-night observational study and were asked to report their sleeping position. This was compared to sleep position as recorded by a night capable video recording. The participants were instructed to settle to sleep on their left side and if they woke overnight to settle back to sleep on their left.

Results: There was a moderate correlation between reported and video-determined left-side sleep time (r = 0.48), mean difference = 3 min (SD = 3.5 h). Participants spent an average of 59.60% (SD = 16.73%) of time in bed on their left side (ICC across multiple nights = 0.67). Those who included left side among their typical sleep positions reported significantly longer sleep during the study (p<0.01).

Conclusions: On average participant reports of sleep position were relatively accurate but there were large individual differences in reporting accuracy and in objectively-determined time on left side. Night-to-night consistency was substantial. For those who do not ordinarily sleep on that side, asking participants to sleep on their left may result in reduced sleep duration. This is an important consideration during a sleep-critical time such as late pregnancy.

Conflict of interest statement

Competing Interests: The authors have declared that no competing interests exist.

Figures

Figure 1

Upper Panel: Scatterplot plus line of best fit for subjective time on left side (x-axis) against video-determined time on left side (y-axis). Middle Panel: Bland-Altman Plot illustrating the relationship between subjective and video measures of time spent on left side. Night1 = filled circles, night2 = grey squares and night3 = grey triangles. Lower Panel: Video-determined percentage of time on left with participants on the x-axis sorted by night1 percentage from smallest to largest.

Figure 2. Proportion of participants including left, right, supine or prone among their typical sleep positions (prior to pregnancy), and among their sleep positions during the past month.

Those reporting that they sleep on their left side only are reported on the far right.