A woman who does not sleep on her left side during the last night of her pregnancy has twice the risk of late stillbirth compared to women who do sleep on their left side, researchers from the University of Auckland reported in the BMJ (British Medical Journal). Although the risk is double, it is still small, the authors add – 3.93 per 1,000 compared to 1.96 per 1,000.

If their findings are confirmed in other studies, this data could be important at a population level.

The risk of stillbirth was also found to be higher among women who got up during the night to go to the toilet once or less on their last night of pregnancy, as well as those who regularly slept during the day during their last four weeks.

Team leader, Tomasina Stacey, a PhD student, said that stillbirth rates have changed little over the last two decades – it is a far too common occurrence.

The investigators spoke to 155 women who gave birth to a stillborn between July 2006 and June 2009. They had all been pregnant for at least 28 weeks. They were all Auckland residents. They were compared to a control group of 310 women who were still pregnant.

They were asked about their sleeping positions during pregnancy, and their sleep-waking up patterns during their last month, as well as the night before they believed their baby had died. They also reported on whether they snored and how often they got up during the night to go to the toilet.

They took into account possible impacting factors, such as smoking status, BMI (body mass index), age and social deprivation level.

Snoring and daytime sleepiness were found not to be linked to late stillbirth risk. However, sleeping regularly during the day was linked to late stillbirth risk; so was longer than average night time sleeping.

The women who slept on their right side or on their backs on the last night of their pregnancy were more likely to have a late stillbirth compared to women who slept in other positions.

Women who frequently got up to go to the toilet at night on their last night were less likely to experience a late stillbirth than those who got up once or less.

The researchers believe that restricted blood flow to the fetus when a mother lies on her back or right side for long periods may help explain this association.

As this is a new observation, further studies are required to confirm these findings before any public health recommendations can be given.

The authors concluded:

“If our findings are confirmed, promoting optimal sleep position in late pregnancy may have the potential to reduce the incidence of late stillbirth.”

Dr. Lucy Chappell, from King’s College London said:

“Any simple intervention that reduces the risk of stillbirth would be extremely welcome” (given that the UK has one of the highest sillbirth rates in the developed world)

Chappell adds that Stacey’s findings should be viewed with caution – there could be several different reasons for them. They are certainly not conclusive.

Chappell concluded:

“A forceful campaign urging pregnant women to sleep on their
left side is not yet warranted.”

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Written by Christian Nordqvist