A new study finds that the odds of having a boy or girl aren’t 50-50. Instead, birth sex is associated with maternal age, specific genes and the sexes of older siblings.

Some people’s biology may set them up to birth babies of a certain sex, explaining why a family with multiple children may have all girls or all boys.

When Nayomie Mejia told her partner to bring a car seat to the hospital, she could never have predicted the "first dad moment" to come.