Stillbirth occurs when a fetus ceases to live after the 20th week of gestation. According to the US National Institutes of Health, numerous causes contribute to this form of pregnancy loss, but it’s impossible in more than half the cases to determine why the pregnancy ended, an alarming statistic that makes stillbirth the subject of vigorous study around the world. A recently published study from the United Kingdom (UK) intensifies the mystery: it finds that the global rate of stillbirth is 10% higher for boy babies than for girls. The study’s authors suggest this new awareness of increased risk may signal the need for gender-based interventions when stillbirth is a known risk.

From England’s University of Exeter, Dr. Fiona Mathews writes that “the disparity between male and female stillbirth rates is startling.” The disparity is consistent around the world and does not vary according to national wealth. In the UK, 11 babies are stillborn every day (one in every 260 UK pregnancies). The UK is one of the world’s wealthiest nations but experiences one of the highest rates for stillbirths.

Mathews and her research team analyzed data from 30 million births around the world. Some findings of their work include:

• Boys are 10% more likely to be stillborn than girls.
• This 10% stillbirth rate accounts for approximately 100,000 male babies lost each  year.
• Regardless of national affluence, the stillbirth rate in every nation has changed very little in the past 15 years.

It’s only in China and India that the stillbirth rate is about the same for male and female babies. The researchers attribute this finding to the prevalence of gender-biased induced abortions in these cultures where sons are favored much more highly than daughters. In both China and India, the rate of female stillbirths is 1.7 times higher than elsewhere.

Current protocols for assessing the risk for stillbirth include on-going monitoring of fetal size and growth rate and the mother’s weight, height, and ethnic origins. Her number of previous pregnancies is also a factor.

Male babies, in general, are larger than female babies. The Mathews research team suggests its findings could lead to closer monitoring of male fetuses that are smaller than normal and the development of gender-based interventions to reduce the number of male stillbirths.

Although the Mathews study did not seek to identify the reasons more boys are stillborn than girls, it does suggest areas of potential concern:

• Growth of the placenta may be different according to the sex of the baby.
• Placental function may vary by gender.
• Male fetuses may be more sensitive to environmental risk factors.

Some environmental risk factors associated with stillbirths include parental smoking habits, obesity, advanced maternal age, and socioeconomic stressors.

Sources:

1. Mathews, Fiona. “Elevated risk of stillbirth in males: systematic review and meta-analysis of more than 30 million births.” BMC Medicine. BioMed Central Ltd. 27 Nov. 2014. Web. 12 Dec. 2014.
2. March of Dimes. “Pregnancy loss: Stillbirth.” March of Dimes. March of Dimes Foundation. Feb. 2010. Web. 12 Dec. 2014.