What causes a baby's skin to turn pink shortly after birth?

Answer 1

At birth, the baby's lungs are filled with amniotic fluid and are not inflated. The baby takes the first breath as its central nervous system reacts to the sudden change in temperature and environment. Once the umbilical cord is cut and the baby takes the first breath, a number of changes occur in the infant's lungs and circulatory system. Increased oxygen in the lungs causes a decrease in blood flow resistance to the lungs, andresistance of the blood vessels in the body increases. Amniotic fluid drains or is absorbed from the respiratory system. The lungs inflate and begin working on their own, moving oxygen into the bloodstream and removing carbon dioxide by exhalation. The increased amounts of oxygen also stimulate a blood vessel near the heart called the "ductus arteriosus" to begin closing. The ductus arteriosus was necessary to the infant in utero to divert blood away from the lungs since they were not being used for oxygenation (that was the job of the placenta). As this transistion process continues, the oxygenated blood is delivered to the tissues causing the skin to become "pink".