Prospective Evaluation of Maternal Sleep Position Through 30 Weeks of Gestation and Adverse Pregnancy Outcomes

In Reply:

We thank Dr. McCowan and colleagues for their comments regarding our article in the October 2019 issue,¹ and we agree with them. Our study examined the relationship between maternal sleep position and adverse pregnancy outcomes through 30 weeks of gestation. Accordingly, data are not applicable to the last trimester of pregnancy. Also, our study had few stillbirths as would be anticipated in a complex longitudinal prospective study. We were careful to state that our data are not applicable to the last trimester of pregnancy and we avoided making clinical recommendations regarding this time period. Nonetheless, we hope that our findings will be reassuring to women during the first two trimesters. Previous dogma supported lateral sleep starting after 20 weeks gestation or after the first trimester, which our findings refute.

Importantly, we also hope that our findings will spur further research about sleep position and pregnancy. Our statement that “case-control studies may be prone to recall bias” was not intended to invalidate the important observations noted in those studies. Although recall bias is an acknowledged limitation of these studies,² our goal is to acknowledge limitations regarding our current knowledge and further a discussion and more studies to refine our ability to optimize sleep and pregnancy. We also want to underscore the potential downsides of advising women regarding sleep position. The link between adequate sleep and perinatal mental health deserves weight and attention. The CRIBBS collaborators have been admirably mindful of these downsides and have taken steps to minimize them.

We support the recommendations of McCowan et al regarding sleep position at the end of pregnancy. Data are imperfect, but their recommendations are based on the best evidence that is currently available. Although we were meticulous about stating that our study is not applicable to the end of pregnancy there is often creep regarding the scope and applicability of clinical data. In addition, we live in a sound-bite culture where headlines or conclusions may be distilled down to “sleeping on your back is safe in pregnancy.” We should not allow the results of this article to be misconstrued and we must all take the time to communicate accurately with women about what we know and don’t know.