Infant feeding. The physiological basis.

A mother's nutritional status during pregnancy has important implications for both her own health and her ability to produce and breast-feed a healthy infant. Knowledge about adequate maternal nutrition during pregnancy is incomplete, however, and there is still considerable debate about the level of extra energy needed by a pregnant woman. A woman's usual nutritional requirements increase during pregnancy to meet her needs and those of the growing fetus. Additional energy is needed because of increased basal metabolism, the greater cost of physical activity, and the normal accumulation of fat as the energy reserve. The protein, vitamin and mineral requirements of the mother also increase during pregnancy, but the precise amounts for the last two are still a matter for discussion. A woman's weight increments during pregnancy vary between privileged and underprivileged communities. In addition to calcium, phosphorus and iron, a mother provides considerable amounts of protein and fat for fetal growth. Placental metabolism and placental blood flow, which are interrelated, are the most critical factors for fetal development.The nutritional requirements of healthy newborns vary widely according to their weight, gestational age, rate of growth, as well as environmental factors. However, recommendations for some components may be derived from the average composition of early human milk and the amounts consumed by healthy, mature newborns who are following a normal postpartum clinical course. The water requirements of infants are related to their caloric consumption, activity, rate of growth, and the ambient temperature. A postnatal weight loss of 5-8% of body weight is usual during the first few days of life in mature newborn infants; in contrast, infants who experienced intrauterine malnutrition lose little or no weight at all.The dynamic process of mother-newborn interaction from the first hours of life is intimately related to successful early breast-feeding. If this process is delayed, however, it may take longer and may be more difficult to achieve. Close mother-infant contact immediately after birth also helps infants to adapt to their new unsterile environment. Because drugs can interfere with bonding and breast-feeding, such substances should be given only when necessary and their effects should be evaluated. In general, young infants, especially newborns, have very irregular feeding intervals. It is advisable for numerous reasons to feed them whenever they indicate a need.