Sleep on your side after 28 weeks of pregnancy — either left or right — and avoid sleeping flat on your back

Going to sleep on your back (supine position) after 28 weeks of gestation is associated with roughly 2.6 times the risk of late stillbirth compared to sleeping on your side. Left and right sides are equally safe; choose whichever side feels comfortable. If you wake up on your back during the night, do not panic — simply roll back onto your side before going back to sleep.

Free. The only friction is consciously adapting sleep posture for individuals accustomed to sleeping supine.

An individual participant data meta-analysis pooling 5 case-control studies across New Zealand, Australia, the UK, and international registries (851 stillbirth cases and 2,257 healthy controls) evaluated maternal going-to-sleep position in late pregnancy (after 28 weeks). Compared to going to sleep on the left side, supine going-to-sleep position was associated with a 2.6-fold increase in late stillbirth risk (adjusted odds ratio aOR 2.63, 95% CI 1.72–4.04). Right-side sleep showed no elevated risk compared to left (aOR 1.04, 95% CI 0.83–1.31). The association remained consistent across maternal BMI categories and fetal growth percentiles. Authors estimated that if all pregnant women after 28 weeks avoided supine going-to-sleep positions, late stillbirths could theoretically be reduced by approximately 5.8% (95% CI 3.2%–9.2%). The UK NHS endorses side sleeping after 28 weeks as a standard risk-reduction recommendation, reassuring mothers that waking up supine is harmless as long as they turn onto their side again.

Controversy: Findings rely on retrospective recall of going-to-sleep position by mothers after stillbirth occurred, introducing potential recall bias. A prospective US cohort of 8,706 nulliparous women evaluated sleep position up to 30 weeks of gestation and found no association between non-left or supine sleeping and composite adverse pregnancy outcomes (aOR 0.99, 95% CI 0.89–1.11); however, the prospective study did not capture sleep position during the third trimester beyond 30 weeks. Because side sleeping has zero cost and carries no clinical risk, major health agencies endorse side-sleeping as prudent precautionary care. High-income country late stillbirth rates range between 1.3 and 8.8 per 1,000 births.

Cronin RS, Li M, Thompson JMD, et al. (2019). An Individual Participant Data Meta-analysis of Maternal Going-to-Sleep Position, Interactions with Fetal Vulnerability, and the Risk of Late Stillbirth. EClinicalMedicine, 10, 49-57. https://doi.org/10.1016/j.eclinm.2019.03.014；Silver RM, Hunter S, Reddy UM, et al. (2019). Prospective Evaluation of Maternal Sleep Position Through 30 Weeks of Gestation and Adverse Pregnancy Outcomes. Obstetrics and Gynecology, 134(4), 667-676. https://doi.org/10.1097/AOG.0000000000003458（备注里的反方研究）；NHS. Stillbirth. https://www.nhs.uk/conditions/stillbirth/