SIGNIFICANTLY INCREASE RISK OF STILLBIRTH IN MALES
A large-scale study
led by the University of Exeter has found that boys are more likely to be
stillborn than girls. Published in the journal BMC Medicine, the study
reviewed more than 30 million births globally, and found that the risk of
stillbirth is about ten percent higher in boys. This equates to a loss of
around 100,000 additional male babies per year.
The results could help
to explain why some pregnancies go wrong. Around a quarter of stillbirths have
no known cause. Of the remainder, many are linked to placental abnormalities
but it is often unclear why the abnormalities occur.
Dr Fiona Mathews from
the University of Exeter said: "The numbers speak for themselves -- the
disparity between male and female stillbirth rates is startling. Stillbirth is
a common occurrence, even in rich countries with good healthcare systems: every
day, eleven babies are stillborn in the UK. Uncovering why male babies are at
higher risk could be a first step towards developing new approaches to
prevention, including sex-specific management of high-risk pregnancies."
Although the incidence
of stillbirth is lower in high-income countries, the study found that 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. Here the data showed equal ratios
of stillbirth in males and females and higher overall stillbirth risks than
other countries. The mortality rates among females in these studies were 1.7
times the expected levels.
The researchers
recommend the routine recording of the sex of stillborn babies. 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 fetuses to environmental factors experienced by
the mother, including obesity, smoking, advanced maternal age, and social
deprivation.
Existing schemes to
detect when babies are not growing properly have reduced stillbirth rates by
providing an early warning system. 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. As male babies are, on average, larger than female,
this information would help identify unusually small male babies at high risk.
Stillbirth rates in
high- and low-income countries have declined very little in the past 15 years.
The UK has one of the
highest stillbirth rates among wealthy nations, with one in 260 of all
pregnancies resulting in stillbirth.
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