The Midlands and North of England Stillbirth Study (MiNESS) found that women who go to sleep in the supine (lying on the back) position have a 2.3-fold increased risk of late stillbirth (after 28 weeks’ gestation) compared with women who go to sleep on their side.
The study led by Professor Alexander Heazell, Clinical Director at the Tommy’s Stillbirth Research Centre at Saint Mary’s Hospital, Manchester, MiNESS is the largest study to examine maternal sleep and late stillbirth.
It looked into 291 pregnancies that ended in stillbirth and 735 women who had a live birth. It confirms findings from earlier studies in New Zealand and Australia that, in the third trimester (after 28 weeks of pregnancy), pregnant women who go to sleep on their back are more likely to have a stillbirth.
Although researchers cannot say for certain why the risk is increased, there are several theories. In the third trimester, when the woman is lying on her back, the combined weight of baby and uterus (womb) puts pressure on the main blood vessels that supply the uterus, and this can restrict blood flow/oxygen to the baby. Other possible explanations include disturbed breathing during sleep, which is worse when a woman sleeps on her back and in overweight or obese women, who also have an increased risk of stillbirth.
The advice to pregnant women is to go to sleep on their side for any episode of sleep in the third trimester, including, going to sleep at night, returning to sleep after any night awakenings and day time naps.
As the going-to-sleep position is the one held longest during the night, women should not be concerned if they wake up on their back, but should simply roll back onto their side.
The MiNESS study did not find a difference in risk between sleeping on the right or left side. One of the previous studies did show that sleeping on the right increased the risk, but as this was not found in the other three studies, the Tommy’s Sleep On Side campaign recommends that women can go to sleep on either side.
Professor Heazell, who is also Senior Clinical Lecturer in Obstetrics at and the University of Manchester and Honorary Consultant at Saint Mary’s Hospital, says:
Around 11 babies are stillborn every day in the UK. Stillbirth is devastating, with long-lasting effects on bereaved parents. Parents want to know why their baby has died, whether it might happen again if they try for another baby and what they can do to avoid further stillbirth.
“At the Tommy’s Stillbirth Research Centre, we work to identify what we call ‘modifiable risk factors’ for stillbirth. These risk factors are things in day-to-day life that increase expectant mothers’ chances of having a stillborn baby that, importantly, the women have the power to alter, either alone or with medical help.”
We believe that identifying, and avoiding, risk factors that are strongly associated with stillbirth will reduce the number of babies who are stillborn. The MiNESS results have implications as they indicate that if women go to sleep on their side in late pregnancy rather than on their back there could be 3.7% reduction in stillbirth.”
The four charities, Action Medical Research, Curekids, Sands and Tommy’s, who funded the research have put out a joint statement:
“This research and campaign was only made possible with funding from our four charities, which are supported by parents who have experienced stillbirth. We hope that this information will help parents and reduce the number of babies who are stillborn each day”