Nutrition of the Neonate - Adjustments of the Infant to Extrauterine Life

Nutrition of the Neonate

Before birth, the fetus derives almost all its energy from glucose obtained from the mother’s blood. After birth, the amount of glucose stored in the infant’s body in the form of liver and muscle glycogen is sufficient to supply the infant’s needs for only a few hours. The liver of the neonate is still far from functionally adequate at birth, which prevents significant gluconeogenesis. Therefore, the infant’s blood glucose concentration frequently falls the first day to as low as 30 to 40 mg/dl of plasma, less than one half the normal value. Fortunately, however, appropriate mechanisms are available for the infant to use its stored fats and proteins for metabolism until mother’s milk can be provided 2 to 3 days later.

Special problems are also frequently associated with getting an adequate fluid supply to the neonate because the infant’s rate of body fluid turnover averages seven times that of an adult, and the mother’s milk supply requires several days to develop. Ordinarily, the infant’s weight decreases 5 to 10 per cent and sometimes as much as 20 per cent within the first 2 to 3 days of life. Most of this weight loss is loss of fluid rather than of body solids.