Low Birth Weight

Low birth weight is more common than stillbirth, affecting 20 million babies annually [1] and increasing infant mortality by twenty times in the first year of life [2].

Assuming a supine position during the third trimester causes significant hemodynamic changes including a reduction of maternal cardiac output and subsequently a reduction in blood flow to the fetus. A study investigating the effect of supine maternal position on birth weight found that women at 28 weeks of gestation or greater who often slept in a supine position had a baby with an average birth weight of 3410g (compared to an average of 3554g for women who did not sleep in a supine position) and a mean reduction of 10% in birth weight centile independent of other factors that affect birth size. There was also a three-fold increase in odds of small for gestational age by INTERGROWTH-21st centiles for women that went to bed in a supine position [3].

A cross-sectional study investigating maternal sleep practices and fetal outcomes for Ghanian women found that maternal supine sleep contributes significantly to pre-eclampsia, low birth weight, and stillbirth [4].

Sources

[1] “Too many babies are born too small,” Who.int. [Online]. Available: https://www.who.int/news/item/16-05-2019-too-many-babies-are-born-too-small.

[2] A. J. Wilcox, “On the importance--and the unimportance--of birthweight,” Int. J. Epidemiol., vol. 30, no. 6, pp. 1233–1241, 2001.

[3] N. H. Anderson et al., “Association of supine going-to-sleep position in late pregnancy with reduced birth weight: A secondary analysis of an individual participant data meta-analysis: A secondary analysis of an individual participant data meta-analysis,” JAMA Netw. Open, vol. 2, no. 10, p. e1912614, 2019.

[4] J. T. Owusu et al., “Association of maternal sleep practices with pre-eclampsia, low birth weight, and stillbirth among Ghanaian women,” Int. J. Gynaecol. Obstet., vol. 121, no. 3, pp. 261–265, 2013.