Before they can make it through childhood, boys face a puzzling challenge making it out of the maternity ward.

Infant deaths in the United States run almost 30 percent higher for males than for females. Scientists don't know why, but they suspect something fragile in the male XY chromosomes.

A 2000 study in the British Medical Journal found that boys in the womb are "at greater risk of death or damage from almost all the obstetric catastrophes," including congenital deformities, brain damage and cerebral palsy.

Even when healthy, the newborn boy tends to lag developmentally behind girls by four to six weeks.

From the nursery on, a strange pattern of vulnerability appears set: Hyperactivity, reading delay, Tourette Syndrome and autism strike three to five times more boys than girls.

Risky behavior in young adulthood only steepens the mortality curve: In 2002, U.S. deaths of people younger than 25 totaled 25,901 females and 47,137 males.

"A typical attitude of boys is that they are, or must be, more resilient than girls," wrote London psychiatrist Sebastian Kraemer in the medical journal report. "This adds social insult to biological injury."