Boys are 10% more likely to be stillborn than girls, a UK study has revealed.
Published in BMC Medicine, the study reviewed more than 30 million births globally, and found that the risk of stillbirth is about 10% higher in boys – about 100,000 additional male babies every year.
Dr Fiona Mathews from the University of Exeter, who recommend the routine recording of the sex of stillborn babies, said ascertaining why boys are at higher risk could be a first step towards developing new approaches to prevention. This would include sex-specific management of high-risk pregnancies.
“The numbers speak for themselves – the disparity between male and female stillbirth rates is startling,” she said.
“Stillbirth is a common occurrence, even in rich countries with good healthcare systems: every day, 11 babies are stillborn in the UK. “
Although stillbirth is lower in high-income countries, the percentage of increased risk of mortality in males was consistent across both high- and low-income countries.
The only exceptions to this global pattern were found in reports from China and India, where sex-biased induced abortion is a known issue.
Dr Mathews said although the reasons for increased risk to male babies are not known, they could include developmental differences in the growth and function of the placenta, or increased sensitivity of male foetuses to environmental factors experienced by the mother, including obesity, smoking, advanced maternal age, and social deprivation.
The routine recording of the sex of stillborn babies could help in the search for an explanation.
She said existing schemes to detect when babies are not growing properly have reduced stillbirth rates. These compare the actual size and growth rate of the baby to predictions based on the mother’s height, weight and ethnicity, and her number of previous babies.
However, they rarely take into account the baby’s gender. Because boys are, on average, larger than girls, this information would help identify unusually small male babies at high risk, added Dr Mathews.
BMC Medicine 27 November 2014
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