Boys a bit more likely than girls to be born early

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

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

The gender difference isn't large: About 55 percent of preterm births in 2010 were male, the report found. Nor is it clear exactly why it happens.

The finding comes from a series of international studies being published Friday that examine newborn health and prematurity. 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 preterm birth and another million die of conditions for which prematurity is an added risk, the researchers calculated.

Friday's report offers some of the first estimates of how many preemie 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 percent of survivors have two of the most burdensome disabilities: neurologic-developmental impairment ranging from learning disabilities to cerebral palsy, and vision loss.

For the public, the gender difference may be the most surprising finding of Friday's report, although Edward McCabe of the March of Dimes said pediatric specialists have long noticed that baby boys start out a bit more vulnerable.

One possible reason: Mothers have a higher risk of certain pregnancy complications - high blood pressure and placenta abnormalities - when carrying boys, Lawn said.

And if a boy preemie and a girl preemie are born at the same gestational age, the boy will be at higher risk of death or disability, she said.