When the umbilical cord is cut and the first breath is taken, these events trigger a rapid change in how mineral metabolism is regulated. The placental infusion and excretion of minerals are abruptly lost, while breathing causes an obligatory increase in blood pH. These alterations provoke a fall in serum calcium and ionized calcium. The intestines become the main source of minerals, the kidneys begin to reabsorb minerals, and bone turnover becomes more important to maintain serum mineral concentrations