There is one thing pregnant women can do to cut their risk of stillbirth by half and that's to sleep on their side during the third trimester.
The Midlands and North of England Stillbirth Study (MiNESS) examined more than 1,000 pregnancies – 291 that ended in a stillbirth and 735 that ended in a live birth – and found that women who slept on their back were 2.3 times more likely to experience a late stillbirth (after 28 weeks gestation) compared to those who slept on their side.
The research, recently published in the British Journal of Obstetrics and Gynaecology, is the largest study to examine the relationship between maternal sleeping patterns and the risk of stillbirth. It backs up previous studies in New Zealand (2011) and Australia (2015).
“This is an important study which adds to the growing body of evidence that sleep position in late pregnancy is a modifiable risk factor for stillbirth," Edward Morris, Vice President for Clinical Quality at the Royal College of Obstetricians and Gynaecologists, said in a press release.
"This new research is extremely welcome as a significant number of stillbirths remain unexplained, particularly those in late pregnancy."
In the UK, roughly one in every 225 pregnancies ends in a stillbirth. In the US, it's one in every 100. But less than 10 percent of stillbirths are the result of a predetermined condition. This means that in over 90 percent of cases, they can be prevented.
And according to the researchers, as many as 130 UK babies could be saved every year if women slept the final three months of pregnancy on their side. (This advice goes for napping too.)
Why exactly sleeping position effects the risk of stillbirth is uncertain but the researchers suggest that it could be because the weight of the baby and the womb pushes down on the blood vessels, restricting blood flow and oxygen to the fetus. Another theory put forward is that sleeping on your back can disturb your breathing pattern.
Still, if you do wake on your back, there is no need to panic.
"What I don't want is for women to wake up flat on their back and think 'oh my goodness I've done something awful to my baby'," Alexander Heazell, clinical director at the Tommy's Stillbirth Research Centre at St Mary's Hospital in Manchester and lead author, explained.
"The question that we asked was very specifically what position people went to sleep in and that's important as you spend longer in that position than you do in any other.
"And also you can't do anything about the position that you wake up in but you can do something about the position you go to sleep."