Supine Sleep Position in Early and Late Pregnancy Tied to Breathing Measures

The supine sleep position during both early and late pregnancy is associated with parameters of sleep-disordered breathing (SDB), but not fetal growth velocity, according to study findings published in the journal Sleep.¹

Objective data are lacking on the association between supine sleep during pregnancy and maternal and neonatal outcomes. Therefore, researchers of a longitudinal study determined changes in sleep position and breathing measures during pregnancy, as well as the link between sleep position and fetal growth and birthweight in high-risk pregnancies.

Participants for the current analysis were enrolled from 2 other studies on maternal sleep.² Study eligibility criteria were adults with singleton pregnancies, with a body mass index (BMI) of at least 27 and gestational age of 13 weeks or less.

The researchers collected on medical history, including comorbidities such as diabetes and chronic hypertension, and reproductive history, such as gestational hypertension, preeclampsia, and the use of in vitro fertilization (IVF).

All participants completed home sleep studies in which breathing and sleep patterns were recorded. Sleep positions and changes in these positions during the night were also noted. In addition, estimated fetal weight and birthweight percentiles were measured using a software.

Three cohorts were included in the analysis: early pregnancy cohort (n=446), longitudinal cohort (n=126), and fetal growth cohort for the secondary analysis (n=83).  

Although predominant supine sleep was based on going-to-bed position in less than half of participants with overweight and obesity, the researchers noted a significant association between sleep-onset position and predominant sleep position in both early and late pregnancy (P =.001 and P <.01, respectively).

Additionally, there were significant changes in sleep position between early and late pregnancy (P =.04), with a reduction in time spent in a predominant supine sleep position from early to late pregnancy (40.7% to 32.9%; P =.015).

In the early pregnancy cohort, respiratory parameters of SDB — measured by respiratory event index (REI) — were increased in predominantly supine vs nonsupine sleepers (3.93 vs 2.45; P =.026).

The researchers also noted that time spent in the supine sleep position was significantly associated with both REI and oxygen desaturation index (ODI; P <.05 for both), especially in the third trimester (P =.036).

Results of the secondary analysis showed no statistically significant association between sleep position and neonatal size (P >.56).

Study limitations included the lack of evidence for sleep position and sleep onset; the small sample size in the fetal growth analysis, which may have resulted in inaccurate conclusions regarding fetal growth velocity and other outcomes; and potential confounding.

“Our findings, that predominant sleep position changes over time and that sleep-onset position is often not an accurate proxy, suggest an important role for objective and longitudinal measurements in sleep research,” the researchers concluded.