The baby's head takes the leading part in the birth. The head has the largest diameter of the body and therefore once it is through, the rest can follow. When the "waters break" the baby is awash in what may be a gush or only a trickle of fluid. She tunnel's her way through the birth canal, a tight squeeze all the way. This can take up to two hours. Contractions in the mother's uterus help her along the way. Finally she arrives. Her head emerges. Her birth cry is brief, soft and pleasant. She is born.