Sleep in the Supine Position During Pregnancy is Associated with Fetal Cerebral Redistribution

Abstract

The supine sleep position in late pregnancy is a major risk factor for stillbirth, with a population attributable risk of 5.8% and one in four pregnant women reportedly sleeping in a supine position. Although the mechanisms linking the supine sleep position and late stillbirth remain unclear, there is evidence that it exacerbates pre-existing maternal sleep disordered breathing, which is another known risk factor for adverse perinatal outcomes. Given that maternal sleep position is a potentially modifiable risk factor, the aim of this study was to characterize and correlate uteroplacental and fetal hemodynamics, including cardiac function, in a cohort of women with apparently uncomplicated pregnancies with their nocturnal sleep position. This was a prospective observational cohort study at an Australian tertiary obstetric hospital. Women were asked to complete a series of questions related to their sleep position in late pregnancy after 35 weeks of completed gestation. They also underwent an ultrasound assessment where Doppler indices of various fetoplacental vessels and fetal cardiac function were measured. Regional cerebral perfusion was also assessed. Pregnancy outcome data was extracted from the electronic hospital database for analysis. A total of 274 women were included in the final analysis. Of these, 78.1% (214/274) reported no supine sleep, and 21.9% (60/274) reported going to sleep in a supine position. The middle cerebral artery, anterior cerebral artery, and vertebral artery pulsatility indices were all significantly lower in the supine sleep cohort, as was the cerebroplacental ratio. There were no significant differences in the mode or indication for delivery or in serious neonatal outcomes, including 5-min Apgar score < 7, acidosis, and neonatal intensive care unit admission between cohorts. Women in the supine cohort were more likely to have an infant with a BW > 90th centile (p = 0.04). This data demonstrates fetal brain sparing in association with the maternal supine sleep position in a low-risk population. This data contributes to the growing body of literature attempting to elucidate the etiological pathways responsible for the association of late stillbirth with the maternal supine sleep position.

Maternal sleep behaviours preceding fetal heart rate events on cardiotocography

“…Despite the women in this study spending a quarter of the night in the supine position, we were surprised to find that supine sleep position was not temporally associated with adverse FHR changes, for neither healthy nor complicated pregnancies. Relationships have been reported between self-reported supine 'sleep onset' during the later stages of pregnancy and fetal wellbeing, including reduced birthweight, fetal cerebral redistribution and stillbirth (Anderson et al 2019;Cronin et al 2019;Robertson et al 2020). There is biological plausibility for the supine position causing detrimental effects including aorto-caval compression resulting in decreased cardiac output (Humphries et al 2019) and impaired utero-placental blood flow (Jeffreys et al 2006).…”

“…2019; Robertson et al . 2020). There is biological plausibility for the supine position causing detrimental effects including aorto‐caval compression resulting in decreased cardiac output (Humphries et al .…”