Now a United Kingdom study has found a link between increased risk of stillbirth and a common sleep position - adding more data to the idea you should try to sleep on your side during the last trimester of pregnancy.
A public health campaign, the Sleep On Side campaign, led by the charity Tommy's to educate women about the risk of going to sleep on their back in late pregnancy, also launches today.
That's a pretty big deal, considering that approximately one in 225 United Kingdom pregnancies ends in stillbirth.
The research also showed that the tragedy of stillbirths are also more likely to occur if women sleep less than 5.5 hours the night before, get up in the night to use the toilet or have a nap every day.
In the late stage of pregnancy the combined weight of the baby and the womb puts pressure on the mother's blood flow when she is lying on her back.
"We know that when women sleep on their backs, venous return [blood flow back to the heart] is compromised, which will also make the woman feel unwell, and so we always encourage women to at least try to sleep on their sides", she tells Global News.
Lead author Professor Alexander Heazell from Tommy's Stillbirth Research Centre at St Mary's Hospital in Manchester, said: "Around 11 babies are stillborn every day in the UK". According to the University of Ottawa, these births are more common in multiple births (the United Kingdom study, however, did not interview women who had multiple births).
A report in the "Mirror" described the study which confirms findings from smaller studies in New Zealand and Australia, as the biggest of its kind.
The study advises that women late in their pregnancies pay attention to their sleeping position and take steps to stay on their side while sleeping. But new research published in the Journal of Physiology also found that babies are only in an active state overnight when their mothers are sleeping on their sides.
The women were interviewed about their sleeping positions amongst a number of other factors. "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".
If you're a mom or mom-to-be, you've likely heard that the safest way to sleep during pregnancy is on your side, as opposed to on your back (or your stomach, obviously). This addition to current knowledge is very welcome.
It's not exactly clear how the sleeping position can affect the baby. The researchers say that this change could decrease stillbirth rates in the United Kingdom by 3.7 percent. "It seems to be related to the night before their baby died", he says.