The answers aren't always clear-cut and there are always exceptions to the rules. But beyond the obvious, there are some interesting differences between boys and girls. When you're marveling at a row of newborns in the hospital nursery, among the flailing fists, the yawns and the cries, it's hard to separate the girls from the boys. But even at birth there are some discernable distinctions between the sexes. They'll often have more problems with their breathing.
Girls also seem to have more protection from infection than boys.
It's not a huge difference, but it's definitely there. They also had greater risks of asthma, intellectual disabilities and developmental delays. But there are no definitive explanations for these differences. When it comes to temperament, parents on playgrounds are always debating which babies are easier, boys or girls. Everyone has an opinion.