Sleeping on your side can cut stillbirth risk

Falling asleep on your back can increase the risk of stillbirth.
Falling asleep on your back can increase the risk of stillbirth. Photo: Supplied

Feeling a level of anxiety is natural for many pregnant women. Not only are our bodies and lives transforming before our eyes, we worry that every thing we eat, think or do might harm our growing baby.

While rates of stillbirth in Australia are comparatively very low (about one per cent of babies are stillborn or die in the first month of life), women can rest easier knowing there are simple changes they can make to further reduce the risks – like sleeping on their side, for instance.

A new study, published in in The Lancet’s EClinicalMedicine, analysed the latest data from around the world and found that going to sleep on your side in the final three months of pregnancy more than halves the risk of stillbirth.

“Going to sleep lying on the back was associated with a 2.6 fold increased risk of stillbirth compared to going to sleep lying on the left side,” said lead author Professor Lesley McCowan from the University of Auckland’s Department of Obstetrics and Gynaecology.

“The left and right sides were equally safe which means pregnant women have a choice of settling to sleep on their left or right side.”

McCowan reassures women that it doesn’t matter what position they wake up in, only the one they fall asleep in.

“It is common to wake up on your back don’t worry - just roll back on to your side,” she said.

Obstetrician Gynaecologist Dr William Milford says the study is “significant” as it confirms existing research and helps to debunk the myth that sleeping on one side was safer than the other.

“The initial concept behind the left sided sleeping was due to the anatomy,” Milford said.

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Most of the rate of blood flow back to the heart from the lower half of the body comes through a large vein called the inferior vena cava, he explains.

“It runs to the right side of the spinal column and hence it is less likely to be compressed (and therefore to reduce cardiac output) if you lie on your left side during pregnancy.”

The research proves the inferior vena cava is not in fact squashed while sleeping on the side, but it is compressed by the womb when the mother sleeps on her back, reducing bloodflow by 80 per cent.

As well as this, the mother’s aorta, which is the main artery from her heart, is also partly compressed, decreasing blood flow to the baby by about 30 per cent.

“While healthy unborn babies can compensate for the reduced blood supply, babies that are unwell or vulnerable for some other reason, may not cope,” Professor McCowan said.

So, the risk of stillbirth was even greater among mothers who were obese or who had a small-for-gestational age baby and who then also went to sleep on their backs.

She added further research is needed but sleeping on the back is unlikely to be a problem before the third and final trimester: “Prior to 28 weeks the uterus is smaller and would be expected to have less impact on reducing the blood flow if the women was lying on her back.”

Milford says the challenge is to educate women without unnecessarily worrying them.

“I think that there is significant anxiety created for pregnant women when, in reality, it is very difficult to do anything that will harm the baby. This includes things about foods, exercise and cosmetic practices,” Milford explains. “The general understanding of these is much more strict than the medical reality and this creates significant amounts of unnecessary anxiety.”

He adds: “Most of the 'big ticket items' in terms of reducing stillbirth are addressing factors such as overweight / obesity, smoking and age as well as the inequalities within our society.

“The unfortunate reality is that most women are far more concerned about eating soft cheese and deli meats than these arguably more important issues.”

According to the researchers of the new study, if all women settled to sleep on their side during the third trimester, this information about sleep could potentially reduce late still birth by approximately 6 per cent.

Sleep advice for pregnant women

From 28 weeks:

  • Settle to sleep on your side to reduce the risk of stillbirth
  • Start every sleep on your side including day-time naps
  • It does not matter which side you
  • It is common to wake up on your back don’t worry- just roll back on to your side