Females are tougher in utero
Two and a half as many boys are conceived as girls, Dr. Legato says, but they’re so much more likely to succumb to prenatal infection or other issues in the womb that by the time they’re born, the ratio is close to one to one. “They’re also slower to develop physically than girls prenatally, which means they’re more likely to die if they are preemies due to underdeveloped lung or brain development,” Dr. Legato explains.