Pregnant women on their third trimester are now being urged to sleep on their side as a way to prevent stillbirth. That's according to a new study which looked at over 1,000 pregnant women and found that sleeping on their backs during the third trimester doubles the risk of stillbirth.

The position women fall asleep in is most crucial, according to the researchers, but they shouldn't worry about waking on their backs.

They looked at 291 women whose pregnancies ended in stillbirth in addition to 735 women who had a live birth. About one in 225 pregnancies ends in stillbirth in the UK, and the researchers claim this could be prevented simply by sleeping sideways.

Published in the British Journal of Obstetrics and Gynaecology, the study is the largest of its kind and seems to confirm certain findings from comparable studies in Australia and New Zealand.

Attention, Pregnant Women: Sleep On Your Side

Alexander Heazell, research lead and clinical director of the Tommy's Stillbirth Research Centre in Manchester, says women in their third trimester must sleep on their side regardless of the episode of sleep, whether daytime, nighttime, or even naps. But again, Heazell reiterates that falling asleep in such a position is what matters, not the position they're in upon waking up.

Heazell says that the falling-asleep position is the most important factor, because it's the one held longest during the night. He also adds that one can't decide what position they're going to wake up in, but can control the position they sleep in.

Beyond urging women to sleep on their side, the researchers can't determine why sleeping on one's back during the third trimester doubles the risk of stillbirth.

They say if the risk was eliminated on a global scale, over 100,000 infants per year could be saved.

A public health campaign has been launched to go along with the publication of the study. It's called "Sleep on Side," and it aims to educate pregnant women about the risk of sleeping on their backs. It specifically targets those who are already on their third trimester, but it will of course help educate other women who are on their way there.

Why Sleeping On One's Back Increases Stillbirth Risks

For now, more research is due. If there's indeed a risk of stillbirth associated with sleeping on one's back, there must be a reason why. One theory suggests that the weight of the baby and the uterus puts pressure on the main blood vessels that supply the uterus, which could restrict blood flow or oxygen to the baby.

There are other factors that possibly increase the risk of stillbirth as well, including air pollution and giving birth via a caesarian section.

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