A full-term placenta holds about six ounces of a fetus’s blood, which is about half of a newborn’s blood volume. The infant needs that blood to be in its body when it makes its way to the outside. So how does it get into the baby’s body in time for it to be born? The mighty uterus and its contractions, which squeeze the placenta, force blood through the umbilical vein and into the fetus.
