A latest study shows that placenta plays an important role in survival battle between male and female babies.

Researchers at the University of Adelaide's Robinson Research Institute studied the primary genetic and developmental reasons why female babies generally have better outcomes than males and why there are significantly increased rates of pregnancy complications and poor health outcomes for males.

For the study, the researchers examined 300 placenta samples. They found that more than 140 genes were expressed differently across male and female samples.

"Our research has found that there are undeniable genetic and physiological differences between boys and girls that extend beyond just the development of their sexual characteristics," senior author of the paper Professor Claire Roberts, leader of the fetal growth research priority for the Robinson Research Institute, said in a press release.

The research team said that girls win the survival battle with better outcomes for female babies in preterm birth, stillbirth, neonatal death, and other complications after birth, such as macrosomia (a baby that weighs more than 4-4.5 kg or 8 pounds 13 ounces at birth). "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," said Roberts.

The study suggests that there is a sex bias in the regulation of genes in the human placenta. The results showed that female babies have more expression of genes involved in placental development, the maintenance of pregnancy and maternal immune tolerance, explained study lead author and University of Adelaide PhD student Sam Buckberry.

"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 said.

The researchers said that the study findings were important as they will help guide future sex-specific therapeutics for pregnant women and for babies in the neonatal nursery.

The findings were published in the journal Molecular Human Reproduction.