Australasian Science: Australia's authority on science since 1938

Sex Discrimination in the Womb

Gene expression in the placenta is responsible for higher rates of pre-term birth, stillbirth and neonatal death among boys, according to research published in Molecular Human Reproduction.

“We've known for some time that girls are clearly winning in the battle for survival,” says Prof Claire Roberts of the University of Adelaide's Robinson Research Institute. “Male babies generally grow faster and bigger than females. This occurs in both the animal and human worlds, but until now we haven't really understood how or why,” she says.

The researchers investigated whether the type and pattern of genes being expressed by the placenta is different for boys and girls. They compared the genes expressed in 300 placenta samples and found that more than 140 genes were expressed differently across male and female samples.

“Our results suggest that there is a distinct sex bias in the regulation of genes in the human placenta,” says lead author Sam Buckberry. “We found that with female babies there is much higher expression of genes involved in placental development, the maintenance of pregnancy and maternal immune tolerance.

“This suggests that girls are more likely to adopt a risk-averse strategy towards development and survival, and it goes some way to explaining the differences in male and female development in the womb,” he says.

Roberts adds: “These findings may be important to help guide future sex-specific therapeutics for pregnant women and for babies in the neonatal nursery.”