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Sleep patterns in late pregnancy associated with stillbirth

Sleeping in any position but left side doubles stillbirth risk

Caroline White

Wednesday, 15 June 2011

Women who  go to sleep in any position but their left side on their last night of pregnancy are twice as likely to give birth to a stillborn child as women who sleep on their left side, finds research published on bmj.com today.

Women who get up to go to the toilet once or not at all on their last night of pregnancy and those who regularly sleep during the day during the last month of pregnancy, are also at heightened risk of a stillbirth.

The absolute risk of late stillbirth for women who sleep on their left side was small at 1.96 per 1000 compared with 3.93 per 1000 for those who slept in any other position.

But if confirmed in other studies, this could be significant at population level, say the authors, who add that stillbirth is still far too common, with little change in the rate over the past 20 years.

The research team interviewed 155 women in Auckland, New Zealand, who gave birth to a stillborn baby between July 2006 and June 2009 when they were at least 28 weeks pregnant. These women were compared with a group of 310 women whose pregnancies were at the same stage and ongoing.

Previous research has indicated an association between sleep disordered breathing and pregnancy complications such as pre-eclampsia and preterm birth, so the authors wanted to find out if sleep patterns had any influence on the rate of stillbirth.

Women were asked detailed questions about their sleep position on going to sleep and waking up before they became pregnant, and during the last month, week, and night before they believed their baby had died. They were also asked about snoring, daytime sleepiness, whether they regularly slept during the day in the last month of pregnancy, how long they slept at night, and how many times they got up to go to the toilet at night.

Information on factors likely to influence the findings, such as age, whether they were smokers, weight, and levels of social deprivation were also taken into account.

Analysis of the data showed no link between snoring or daytime sleepiness and risk of late stillbirth. But sleeping regularly during the day was significantly associated with late stillbirth risk, as was longer than average night time sleeping.

Women who slept on their back or on their right side on the night before stillbirth were also more likely to experience a late stillbirth than women who slept on their left side. Women who got up to the toilet once or not at all on the last night were also more likely to experience a late stillbirth than women who got up more frequently.

The authors suggest that blood flow to the baby may be restricted when the mother lies on her back or right side for long periods, which may help to explain their findings.

In an accompanying editorial, Dr Lucy Chappell from King's College London, says that as the UK has one of the highest rates of stillbirth in the developed world "any simple intervention that reduces the risk of stillbirth would be extremely welcome."

But she says there could be several explanations for the findings and that the research results are certainly not conclusive. Dr Chappell concludes that "a forceful campaign urging pregnant women to sleep on their left side is not yet warranted" and that at this stage, the study only puts forward a theory.

Ms Daghni Rajasingam, spokesperson, for the Royal College of Obstetricians and Gynaecologists said many factors have been linked to stillbirth, including obesity, older maternal age, ethnicity, congenital anomalies and placental conditions. “A significant number are unexplained,” she added. 

“This small scale study looks at another possible factor, however, more research is needed into sleep patterns before any firm conclusions over sleeping positions can be made. In the meantime, women should speak to their midwives if they are concerned,” she advised.

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