Image copyright Getty Images Image caption Most pregnant women tend to have lower levels of the disease than those of a dark complexion
Several countries have reported increases in stillbirths among black and mixed-race women, a study suggests.
The number of stillbirths for women of mixed race and darker skin-tone has risen by up to 60% from 2007 to 2017.
New research shows the rates are five times as high in some states – Alaska and the US territories of Guam, Puerto Rico and American Samoa.
While stillbirths have increased in all races, they are particularly high in black women.
The World Health Organisation estimates that around 6,000 babies worldwide die per day of “preventable conditions”.
Image copyright Getty Images Image caption Preterm births are a particular risk
Half of these are newborns, with babies under one month old among the biggest killers.
Now researchers at the Karolinska Institute in Sweden have used DNA research from the 25,000 most recently-recorded cases of stillbirth to map how each race’s population matches their own community, and work out how stillbirth rates change over time.
They found the places with the highest “elevated” rates of stillbirths – such as in the US state of Alaska – were far more varied than others.
Overall, although rates in the UK are falling, they remain high among some groups, such as black, white and mixed-race people.
Period of “terrible” change
The researchers suspect the reasons for the rise are that women of mixed race and darker skin tone are opting for heavier pregnancies, which can increase the risk of stillbirth.
Dr Lillian Roggenauer from the Karolinska Institute told BBC News that this makes sense as dark skin tones have a lower level of cholesterol, making them more metabolically active.
But in terms of the reason for the rise in the numbers of stillbirths in specific communities, she said these might involve other causes too.
“We know the rates are moving because they are also influenced by characteristics such as socio-demographics,” she said.
Image copyright Getty Images Image caption Black women are most at risk of stillbirth in the US
“But what we don’t know is whether this is caused by some medical condition or just by genetics or environmental factors.”
The study looked at births in Norway, Sweden, Finland, and the US state of Alaska.
The research looked at low birth-weight deliveries or preterm birth, and used DNA profiling of newborns and the mothers.
Dr Roggenauer said the results – which were published in JAMA – suggest the women who had been most affected were black and mixed-race, for whom the risk of stillbirth had gone up by more than 60%.
Dr Roggenauer said she could not explain why these women may have had the highest risks, but some could have been taking birth control that was, to some extent, abortive.
She said these women could have died before the fall in numbers of stillbirths began, but it was likely they were still passing on their patterns to their own children.
“There must be a drop and it’s only becoming evident now because of DNA data,” she said.
“That’s why I think it’s a terrible change and must be reversed.”
Dr Roggenauer said she hoped that data like this could serve as a warning that “we have to work together” to cut the numbers of stillbirths and deaths.
Over the past decade, British doctors have been increasingly involved in creating clinical trials to find ways to reduce the number of babies born too early and too small.
Dr Zakia Khatun-Patel, chair of the Royal College of Obstetricians and Gynaecologists said that maternity research was also being used to identify which women are at the highest risk of stillbirth – and help find ways to reduce the risk.
“We hope this will lead to more coordinated public health efforts aimed at reducing the number of stillbirths,” she told BBC News.