Infrared cameras study found pregnant women should sleep on their side

13 October 2017
Pregnant woman

New University of Auckland research has found that expectant mothers should sleep on their side towards the end of pregnancy, after the research found that women who sleep on their backs in late pregnancy may cause problems for the baby.
The researchers, led by Professor Peter Stone of the Faculty of Medical and Health Sciences, monitored both unborn babies and their mothers overnight to observe the effects of sleeping positions.
The study, published in The Journal of Physiology, saw 29 healthy women who were 34 to 38 weeks pregnant given fetal electrocardiogram recordings overnight to monitor the heart and the baby’s activity.
The researchers used an infrared video camera to record the position of the women sleeping. They also had a position monitor attached to the mother and a fetal heart rate monitor attached to mother’s abdomen, which continuously recorded the fetal heart beat overnight.
Fetuses were only in an active state when the mother was on her left or right side.
When the mother changed position during sleep, for example from her left side to sleeping on her back, the baby quickly changed activity state and became quiet or still, they found.
“What we found was that when the mother slept on her back, the baby became less active, which conserves oxygen. We found that the babies were only in an active state when the mother was on her left or right side. When the mother changed position during sleep, for example from left to back sleeping, the baby quickly changed activity state.”
Previous studies have linked the position a mother sleeps in with an impact on the baby's risk of still birth - compared with sleeping on the left side, lying flat facing upwards was found to be linked to an increased risk of stillbirth.
“The research used women who were very healthy with healthy babies. We speculate that the effects we saw in healthy babies would be that much more severe and significant in a fetus with problems.”
"In the situation where the baby may not be healthy, such as those with poor growth, the baby may not tolerate the effect of maternal back-sleeping," he says.
"We are suggesting that there is now sufficient evidence to recommend mothers avoid sleeping on their back in late pregnancy, not only because of the epidemiological data but also because we have shown it has a clear effect on the baby."
This was the first study to monitor unborn babies overnight and at the same time record the mother’s position during sleep.
“This enabled us to relate the baby’s activity to the mother’s sleep position. This is important because recently we and now other groups have shown that the mother’s sleep position is related to the risk of late stillbirth after 28 weeks gestation.
“Following this study we are now carefully investigating pregnancies where the baby is not growing properly, or the mother has reported decreased baby movements; both situations we know have an increased risk of stillbirth.”
The research was conducted by the University’s Maternal Sleep in Pregnancy Research group that also includes Professors Ed Mitchell, Lesley McCowan and Alistair Gunn, Associate Professor John Thompson, Dr Kevin Ellyett and Dr Andy Veale.
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