Tossing and turning during pregnancy may be frustrating and exhausting but, according to a new study, it could actually be a way of protecting unborn babies. New research, published in the journal Birth, found that long periods of undisturbed sleep, specifically more than nine hours, was associated with late stillbirth.
"Blood pressure reaches its lowest point during sleep but when someone wakes up there is a surge in the nervous system activity that causes increases in blood pressure," says co-author Associate Professor Jane Warland of the University of South Australia. "This is important because low blood pressure has been linked with fetal growth problems, pre-term birth and stillbirth."
As part of the study, a team of researchers from Australia, the UK, the US and New Zealand surveyed 153 women who had experienced a late stillbirth (after 28 weeks of pregnancy), and 480 women who had recently delivered a healthy baby. Women were asked a number of questions around their typical nighttime sleep duration, daytime nap duration, number of awakenings, number of times they got out of bed to use the bathroom, restless sleep, sleep quality, and whether medications were used to help them sleep.Participants were also asked questions related to established risk factors for stillbirth, including smoking and fetal movements.
The team found that long periods of undisturbed sleep, such as long sleep duration and not waking more than once, independent of other risk factors, were associated with stillbirth in the third trimester.
"It is plausible that awakenings and periods of getting out of bed (such as to use the toilet) in pregnant women could serve to maintain blood pressure and prevent long periods of relative low pressures," the authors write, noting that the findings warrant further investigation.
"Pregnant women often report waking up and getting up in the middle of the night," says lead author Dr Louise O'Brien. "While multiple awakenings during the night may concern some women, in the context of stillbirth it appears to be protective." But Dr O'Brien adds that women should not be "waking themselves up at night" as very disruptive sleep has also been associated with poor pregnancy outcomes, including growth restriction and preterm growth.
"Our findings add to research indicating that maternal sleep plays a role in fetal wellbeing," she says. "Studies aiming to reduce stillbirths should consider maternal sleep as this is a potentially modifiable risk factor. Understanding the role of maternal sleep may help us identify interventions that would put us in a better position to advise women."
The research follows a number of studies which have found that the risk of stillbirth is doubled if women fall asleep on their backs in the third trimester. The most recent, the largest examination of maternal sleep position and risk of stillbirth to date, also found a link between short and long duration sleep on the last night, getting up to the toilet only once or not at all on the last night, and daytime napping every day.
A landmark Senate report released last year, noted that the rates of stillbirth in Australia have remained unchanged in two decades. Six babies are born still every day, with the rate of stillbirth for Aboriginal and Torres Strait Islander babies double that of other Australian women (13 in 1,000 births compared to six in 1,000 births).