An analysis of the individual participant Meta-analysis of the maternal position going to sleep, interactions with fetal vulnerability and the risk of late fetal death



The supine lying position of the mother has been associated with an increased risk of late fetal death (≥28 weeks), but it is unknown if the risk differs between the right side and the left side, and whether some pregnancies are more vulnerable.[3]Methods

Systematic surveys were conducted for a meta-analysis of individual-level participant data (IPD) from case-control studies, prospective cohort studies, and randomized trials conducted up to January 26, 2018, which reported data on the maternal position of going to sleep and stillbirths. Participant inclusion criteria included gestation ≥28 weeks, single and non-anomalous pregnancies. The primary outcome was stillbirth. A stratified study-site approach was used for meta-analysis. The interaction between the supine position going to sleep and fetal vulnerability was assessed by bi-variable regression. The multivariate model was adjusted for confusions a priori. Registration number: PROSPERO, CRD42017047703.


Six case-control studies were identified, with data obtained from five (cases, n = 851, controls, n = 2257). No data were provided by a sixth study (cases, n = 100, controls, n = 200). The supine position going to sleep was associated with increased odds of late fetal death (adjusted odds ratio [aOR] 2.63, 95% CI 1.72-4.04, p <0.0001) compared to the left side. The right side had similar chances to the left (aOR 1.04, 95% CI 0.83-1.31, p = 0.75). There were no significant interactions between the supine position of going to sleep and indicators of fetal vulnerability, including small babies for gestational age (p = 0.32), maternal obesity (p = 0.08), and smoking (p = 0 , 86). The attributable population risk for the supine position going to sleep was 5.8% (3.2 to 9.2).


This IPD meta-analysis confirms that the supine position going to sleep is independently associated with late fetal death. Going to sleep on the left or right side seems equally safe. No significant interactions were identified with our indicators of fetal vulnerability, therefore the supine position of going to sleep may be considered a factor that contributes to late fetal death in all pregnancies. This finding could reduce later stillbirths by 5.8% if all pregnant women of at least 28 weeks resolved to sleep on their side.[10]Key words