Their study suggested that maternal sleep habits, including lengthy periods of sleep without waking more than once in the night, may be associated with foetal health.
“Our findings add to research indicating that maternal sleep plays a role in foetal wellbeing”
The researchers analysed online surveys involving 153 women who had experienced a late stillbirth – on or after 28 weeks of pregnancy – within the previous month and 480 women with an ongoing third-trimester pregnancy or who had recently delivered a live born baby during the same period.
The findings, published in the journal Birth, suggest an association between lengthy periods of undisturbed maternal sleep and stillbirths that were independent of other risk factors.
However, the researchers cautioned that further research was needed to better understand the relationship and what it means for pregnant women.
Lead author Dr Louise O’Brien, from the University of Michigan, said: “Pregnant women often report waking up and getting up in the middle of the night.
“While multiple awakenings during the night may concern some women, in the context of stillbirth it appears to be protective,” she said.
Dr O’Brien highlighted that further studies needed to delve deeper into what may drive the relationship between maternal sleep and stillbirths, with a particular focus on how the autonomic nervous system and the hormonal system were regulated during sleep in late pregnancy.
“We should be looking at every possible intervention that may prevent poor outcomes”
She noted that blood pressure reached its lowest point during sleep but when someone woke there was a surge in nervous system activity that caused transient increases in blood pressure.
It was possible that these brief increases in blood pressure were able to prevent long periods of relatively low pressure, suggested Dr O’Brien.
This was important, she said, because low blood pressure had been linked with foetal growth problems, preterm birth, and stillbirth.
In addition, she cautioned that “pregnant women should not be waking themselves up at night”. Very disruptive sleep has previously been associated with poor pregnancy outcomes, including growth restriction and preterm growth, she warned.
The researchers said there was already evidence that very disrupted sleep and clinical sleep disorders were associated with poor pregnancy outcomes, but few studies had previously looked at long periods of undisturbed sleep.
“Our findings add to research indicating that maternal sleep plays a role in foetal wellbeing,” said Dr O’Brien, highlighting that maternal sleep was 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,” she noted.
“Maternal sleep has been overlooked as a potential area for maternal and newborn health interventions, even though it is related to many of the major, well-established risk factors for poor pregnancy outcomes,” she said. “Until recently, it hasn’t been on the radar for stillbirth research.”
“Understanding the role of maternal sleep may help us identify interventions”
She added: “Many risk factors for stillbirths are not able to be modified once pregnancy has begun. But we should be looking at every possible intervention that may prevent poor outcomes.
Meanwhile, she highlighted that smoking, advanced maternal age, diabetes, obesity and drug abuse were among well-established risk factors for stillbirths.