Pregnant women in Ghana who slept on their backs were at heightened risk of stillbirth compared with women who did not, U.S. researchers say. Senior author Louise O'Brien, an associate professor in University of Michigan's Sleep Disorders Center, and colleagues and said although the study was conducted in a maternity hospital in Ghana, a recent case-control study from New Zealand also found a link between maternal supine sleep -- sleeping on their backs -- and stillbirth. Stillbirth occurs in about two to five babies out of every 1,000 babies born in high-income countries, but undeveloped countries about 20-50 babies out of every 1,000 babies are stillborn, O'Brien said. "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 in a statement. "In Ghana, inexpensive interventions are urgently needed to improve pregnancy outcomes. 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 said the possibility that supine sleep has a part in low-birth weight and subsequently in stillbirths was plausible because of uterine compression resulting in reduced venous filling and cardiac output. "The data in this study suggests that more than one-quarter of stillbirths might be avoided by altering maternal sleep position," O'Brien said. "This supports the need to develop simple intervention trials."