Boys more likely to be born premature than girls, says study

Boys are slightly more likely to be born premature than girls, and they tend to fare worse, says a new report on the health of the world's newborns.

"It's a pattern that happens all over the world," said Dr Joy Lawn of the London School of Hygiene and Tropical Medicine, who led the team of researchers.

The sex difference isn't large: about 55 per cent of premature births in 2010 were male, the report found. It's not clear exactly why it happens.

The finding comes from a series of international studies published yesterday that examine newborn health and premature births. About 15 million babies worldwide are born too soon, most of them in Africa and parts of Asia where survival is difficult for fragile newborns. Globally, about one million babies die as a direct result of premature birth and another million die of conditions for which prematurity is an added risk, the researchers calculated.

Lawn's report offers the first estimates of how many pre-term survivors go on to suffer certain disabilities, and found that where these babies are born and how early determines their risk.

Overall, Lawn said about 7 per cent of survivors have two of the most burdensome disabilities: neurologic-developmental impairment ranging from learning disabilities to cerebral palsy, and vision loss.

But the biggest risk is to those born before 28 weeks of gestation. Worldwide, 52 per cent of them are estimated to have some degree of neuro-developmental impairment, the report found.