Baby boys are at greater risk of pregnancy complications, study suggests

Pregnant women carrying baby boys are more likely to experience serious pregnancy complications than those carrying girls, a new Australian study suggests. But researchers urge expectant mums not to be alarmed, just aware of the potential risks as they plan their prenatal care.

After looking at more than half a million births in Australia, researchers from the Robinson Research Institute at the University of Adelaide say a baby’s gender is linked to the health of both mother and child.

“The major conclusion of our study is that the evidence is there and it is very clear: the sex of the baby has a direct association with pregnancy outcomes,” research leader and senior author Professor Claire Roberts says.

While there is no evidence that a baby’s gender causes the complications, the study found boys were more likely to be born early and therefore more likely to face the associated health issues.


The research team evaluated more than 574,000 Australian births from 1981 through 2011.

This population-based study is the first of its kind in Australia to confirm differences in birth outcomes based on the baby’s gender.

The team found that compared to girls, boys had a 27 per cent higher chance of preterm birth between 20 and 24 weeks’ gestation, 24 per cent higher between 30 and 33 weeks and 17 per cent greater for delivery at 34 to 36 weeks.

Gestational diabetes and at-term pre-eclampsia were also slightly more common among women carrying boys. But, pregnant women carrying a girl have a 22 per cent higher risk for early onset pre-eclampsia requiring a pre-term delivery.

Lead author Dr Petra Verburg says more research is needed.

“Our results indicate there may be a need for specific interventions tailored to male and female babies, to prevent adverse outcomes for both child and mother,” Dr Verbug says.

“We’re investigating other factors that may predict pregnancy complications, taking fetal sex into account.”

Professor Roberts and her team have previously published on gender differences in the expression of 142 genes in the placenta from normal pregnancies.

“The placenta is critical for pregnancy success,” Professor Roberts says.

“We believe that sex differences in placental function may explain the differences we’re seeing in outcomes for newborn boys and girls, and their mothers.

“The next step is to understand the consequence of these differences and how they influence the path to pregnancy complications.”

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Dr Roberts told Health Day expectant mums should not be alarmed by the results, and suggests all women planning a pregnancy should eat well and maintain a healthy weight before conception to reduce their risks of pregnancy complications, regardless of the gender.

Verburg also told Health Day, even if the pregnancy comes as a surprise, “there is still a window of opportunity for a woman to reduce her risks for pregnancy complications” by giving up smoking , alcohol and staying fit.

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