Restless Sleep In Late Pregnancy, Lower Stillbirth Risk

Press Release – University of Auckland

Restless sleep in late pregnancy is common, and researchers have now found it carries a lower risk of late stillbirth.

A University of Auckland-led mega-study combined all the worldwide data from studies on sleep position and stillbirth. For the first time, it revealed that pregnant women who reported more-than-average restless sleep in their third trimester were 38 percent less likely to suffer a stillbirth.

“Pregnant women are often told that the commonly reported restless sleep of late pregnancy is preparing them for night waking with their new baby. It may also be that restless sleep is protecting their unborn baby from stillbirth,” says lead author Robin Cronin, PhD student in the University of Auckland’s School of Medicine and a midwife.

Analysis also showed that frequent snoring (three nights a week or more), reported by nearly a quarter of women during late pregnancy, was not a risk factor for stillbirth. However, sleeping for longer than nine hours at night, or having a daytime nap every day was linked to greater stillbirth risk (by a factor of about 1.5).

“We need to better understand factors associated with long sleep duration and daily daytime naps before we can make any recommendations to pregnant women,” says Mrs Cronin.

“Meanwhile, our advice around sleep in pregnancy remains the same: start every sleep, including daytime naps, on your side. If you wake up on your back, this is normal and don’t worry, just roll onto your side.”

Last year, the same research team published a meta-analysis showing that women who go to sleep lying on their back in the last three months of pregnancy are more than twice as likely to have a stillborn baby, compared with women who go to sleep on their side. This is thought to be due to pressure from the unborn baby inside the womb compressing a major vessel in the mother’s abdomen (the inferior vena cava) and reducing blood supply to the placenta and baby when the mother goes to sleep lying on her back.

The researchers speculate that long overnight sleep and daily daytime naps during late pregnancy may increase the duration of pregnant women’s inactivity, potentially increasing the amount of time they spend sleeping their backs over a 24-hour period.

Mrs Cronin: “We also know that rolling pregnant women from their back to their side can help a baby who becomes distressed during labour, so it’s possible that a mother’s body movement during sleep may improve the supply of blood and oxygen to her unborn baby. This protection from stillbirth with restless sleep could partly explain the relationship we have seen between settling to sleep on your back and an elevated risk of stillbirth.”

The research was funded by Cure Kids New Zealand and Red Nose Australia. The findings are published in the medical journal PLOS ONE.

PLOS ONE: Associations between symptoms of sleep-disordered breathing and maternal sleep patterns with late stillbirth: Findings from an individual participant meta-analysis

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