New research from Auckland University suggests that pregnant women who sleep on their back could be putting the baby at risk of being stillborn.
The study showed that mothers who slept on their back during the final three months of pregnancy were almost four times more likely to stillbirth, due to a decrease in circulation and oxygen to the baby.
Researchers say that changing the way New Zealand expectant mothers sleep could save the lives of about 15 babies per year.
Professor Lesley McCowan, who led the study, said the research was important as stillbirths could be prevented if mothers were warned.
"Public health education encouraging women to go to sleep on their side in the last three months of pregnancy needs to be considered," she said.
"This simple intervention has the potential to reduce late stillbirth by approximately nine per cent.
"Our findings make sense as lying on the back in late pregnancy is associated with physical effects that can compromise the baby's wellbeing.
"These include a reduction in the mother's cardiac output (the amount of blood pumped by the heart per minute), a reduced blood flow to the uterus, and lower oxygen levels in the baby."