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Multicenter Study
. 2017 Jun 13;12(6):e0179396.
doi: 10.1371/journal.pone.0179396. eCollection 2017.

Going to Sleep in the Supine Position Is a Modifiable Risk Factor for Late Pregnancy Stillbirth; Findings From the New Zealand Multicentre Stillbirth Case-Control Study

Free PMC article
Multicenter Study

Going to Sleep in the Supine Position Is a Modifiable Risk Factor for Late Pregnancy Stillbirth; Findings From the New Zealand Multicentre Stillbirth Case-Control Study

Lesley M E McCowan et al. PLoS One. .
Free PMC article


Objective: Our objective was to test the primary hypothesis that maternal non-left, in particular supine going-to-sleep position, would be a risk factor for late stillbirth (≥28 weeks of gestation).

Methods: A multicentre case-control study was conducted in seven New Zealand health regions, between February 2012 and December 2015. Cases (n = 164) were women with singleton pregnancies and late stillbirth, without congenital abnormality. Controls (n = 569) were women with on-going singleton pregnancies, randomly selected and frequency matched for health region and gestation. The primary outcome was adjusted odds of late stillbirth associated with self-reported going-to-sleep position, on the last night. The last night was the night before the late stillbirth was thought to have occurred or the night before interview for controls. Going-to-sleep position on the last night was categorised as: supine, left-side, right-side, propped or restless. Multivariable logistic regression adjusted for known confounders.

Results: Supine going-to-sleep position on the last night was associated with increased late stillbirth risk (adjusted odds ratios (aOR) 3.67, 95% confidence interval (CI) 1.74 to 7.78) with a population attributable risk of 9.4%. Other independent risk factors for late stillbirth (aOR, 95% CI) were: BMI (1.04, 1.01 to 1.08) per unit, maternal age ≥40 (2.88, 1.31 to 6.32), birthweight <10th customised centile (2.76, 1.59 to 4.80), and <6 hours sleep on the last night (1.81, 1.14 to 2.88). The risk associated with supine-going-to-sleep position was greater for term (aOR 10.26, 3.00 to 35.04) than preterm stillbirths (aOR 3.12, 0.97 to 10.05).

Conclusions: Supine going-to-sleep position is associated with a 3.7 fold increase in overall late stillbirth risk, independent of other common risk factors. A public health campaign encouraging women not to go-to-sleep supine in the third trimester has potential to reduce late stillbirth by approximately 9%.

Conflict of interest statement

Competing Interests: The authors have declared that no competing interests exist.


Fig 1
Fig 1. Relationship between BMI and late stillbirth risk.

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Grant support

Funding was provided by: the Health Research Council of New Zealand (ref: 12/372,; Cure Kids (Grant number: 5357,; Mercia Barnes Trust (; Nurture Foundation (; University of Auckland Faculty Research Development Fund (Grant 3700696). Funding sources had no role in study design, data collection, analysis, interpretation, writing the report, or decision to submit the paper for publication.