In the study, researchers from University of Michigan found that supine sleep increased the risk of low birth weight by a factor of 5 and that it was the low birth weight that explained the high risk for stillbirth in these women.
The study's senior author, Louise O'Brien, Ph.D., M.S., associate professor in U-M's Sleep Disorders Center, said that although this study was conducted in a maternity hospital in Ghana-a country that has high perinatal mortality-a recent case-control study from New Zealand also found a link between maternal supine sleep and stillbirth.
Stillbirth is a traumatic event that occurs in about 2-5 babies out of every 1,000 babies born in high-income countries.
In low income countries, such as those in Africa, about 20-50 babies out of every 1,000 babies are stillborn.
"But if maternal sleep position does play a role in stillbirth, encouraging pregnant women everywhere not to sleep on their back is a simple approach that may improve pregnancy outcomes," O'Brien said.
Sub-Saharan Africa has the highest rate of stillbirth in the world and little progress has been made in reducing those deaths.
"In Ghana, inexpensive interventions are urgently needed to improve pregnancy outcomes. This is a behavior that can be modified: encouraging women to avoid sleeping on their back would be a low-cost method to reduce stillbirths in Ghana and other low-income countries," O'Brien added.
The study is published in the International Journal of Gynecology and Obstetrics.