Cervix dilation and breaking water happen twelve hours before birth {birth, reproduction}| {nativity}. Fetus comes out head first, with face toward spine, taking 20 to 60 minutes. After cutting umbilical cord, umbilical arteries and veins close. Carbon-dioxide buildup causes first breath to start. At birth, heart blood flow changes direction. Head pressure can cause brain blood-vessel hemorrhage, and little breathing and low oxygen are dangers.
Biological Sciences>Zoology>Organ>Reproduction>Birth
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Date Modified: 2022.0224