April 8 (UPI) -- The risk of stillbirth may increase when a pregnant woman sleeps on her back during the late phase of gestation, new research shows.
A study published this month in The Lancet found that in many such births, the mothers slept on their backs 28 weeks into the pregnancy.
The findings come from a study conducted in New Zealand that led to more research on the subject in Australia, New Zealand, the United Kingdom and the United States.
"In later pregnancy (after 28 weeks), it is safer to go to sleep on your side than on your back," the study authors said. "A woman who wakes up on her back shouldn't worry, but should settle to sleep again on her side."
The researchers say when pregnant women sleep on their backs, the weight of the uterus decreases the blood flow to the baby.
In the United States, stillborn births account for about 1 percent of pregnancies, or roughly 24,000 births annually, according to the Centers for Disease Control and Prevention.
"The next phase is to ensure that there is consistent advice from healthcare professionals and we will be looking to see if there are ways of helping to support women to sleep in the side position. Only a small proportion of women will be affected," Stacey said. "But the studies that we did following the first findings suggested that women were quite happy to change their going to sleep position if it was better for their babies."