At 38-40 weeks the fetus is considered full-term. Lanugo is gone except on upper arms and shoulders. Hair on the baby's head is now coarser and thicker. The lungs are mature. The average weight of the baby at this point is seven and a half pounds.

At birth the placenta detaches from the uterus and the umbilical cord will be cut as the baby takes his first breaths of air. Breathing will trigger changes in the heart and bypass arteries forcing all blood to now travel through the lungs.