Can sleeping habits predict late stillbirth?

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In high-income countries, 1.3 to 8.8 births per 1000 are late stillbirths. Because these fetal deaths at ≥ 28 weeks often occur in women with no established risk factors, research to identify potentially modifiable behaviors is needed. A new study looked at whether maternal practices play a role. 

Published in Birth, the results are from an analysis of data on an international cohort. Between September 2012 and August 2014, women were invited to participate in an anonymous online survey distributed across social media and through web-based advertising and word-of-mouth. All of them were at least 18 years old, fluent in reading and writing English, and had delivered a singleton stillborn baby at least 28 weeks’ gestation within 1 month before completing the questionnaire. Controls were also at least 18 years old and either still pregnant (≥ 28 weeks) or had delivered a living baby within the month before responding. 

Median duration of time since childbirth in the 480 controls was 13 days (range 1-29 days). Median gestation at time of stillbirth in the 153 cases was 37 weeks (range 28-41 weeks) and 52% of stillbirths were male. 

The authors found no differences in self-reported sleep practices before pregnancy in cases and controls. In the last month of pregnancy, however, nocturnal sleep duration was significantly longer in cases versus controls, as was 24-hour sleep duration. 

Women with stillbirths were at significantly higher odds (aOR 1.75 [95% CI 1.10-2.79]) of sleeping ≥ 9 hours a night in the month before delivery. They were also more likely to report not waking up or waking up only once on the last night before delivery. Although no relationship was found between stillbirth and reported sleep position, the authors noted that the number of reported supine sleepers included in the study was universally low, which prevented full analysis. 

Having restful sleep was more likely in the stillbirth group in the last month, even after accounting for other risk factors (aOR 1.73 [95% CI 1.03-2.99]). Odds of good/very good sleep quality in the last month were higher in the stillbirth group (OR 1.69 [95% CI 1.03-299]). A small number of women reported using sleep aids during the last month and on the last night before taking the survey, but no significant relationship was found with stillbirth. Women in the stillbirth group were also asked about their perception of when their baby died and 74% (n=83) believed it was during the night.

The authors believe their findings suggest that long periods of undisturbed sleep are associated with a late stillbirth. Reports of higher-quality sleep and lack of restless sleep were also more likely in the stillbirth group.

Among identified limitations of the study was lack of availability to women without Internet access, recall bias about sleeping habits, and the fact that, although this was an international study, the majority of participants were from the United States. Ultimately, the authors believe that further physiological studies are necessary about how neuroendocrine and autonomic system pathways are regulated during sleep in the context of late pregnancy