premature infant, any neonate, regardless of birth weight, born before 37 weeks of gestation. Because exact gestational age is often difficult to determine, low birth weight is a significant criterion for identifying the high-risk infant with incomplete organ system development. Predisposing factors associated with prematurity include multiple pregnancy, toxemia, chronic disease, acute infection, sensitization to blood incompatibility, any severe trauma that may interfere with normal fetal development, substance abuse, and teenage pregnancy. In most instances the cause is unknown. The incidence of prematurity is highest among women from low socioeconomic circumstances, for whom poor nutrition and lack of prenatal medical care are often precipitating factors. The premature infant usually appears small and scrawny, with a large head in relation to body size, and weighs less than 2500 g. The skin is thin, smooth, shiny, and translucent, with the underlying vessels clearly visible. The arms and legs are extended, not flexed, as in the full-term infant. There is little subcutaneous fat, sparse hair, few creases on the soles and palms, and poorly developed ear cartilage. In boys the scrotum has few rugae, and the testes may be undescended; in girls the labia gape and the clitoris is prominent. Among the common problems of the premature infant are variations in thermoregulation, chilling, apnea, respiratory distress, sepsis, poor sucking and swallowing reflexes, small stomach capacity, lowered tolerance of the alimentary tract that may lead to necrotizing enterocolitis, immature renal function, hepatic dysfunction often associated with hyperbilirubinemia, incomplete enzyme systems, and susceptibility to various metabolic upsets, such as hypoglycemia, hyperglycemia, and hypocalcemia. The degree of complications and the rate of survival of premature infants are directly related to the state of physiological and anatomical maturity of the various organ systems at the time of birth, the condition of the infant other than prematurity, and the quality of postnatal care. With treatment in a neonatal intensive care unit, survival rates improve yearly. In increasing numbers of very small babies, development is normal, and those who do not have seizures or apneic spells in the first few days are unlikely to suffer neurological or physical sequelae of their prematurity. Of primary concern for the nurse caring for the premature infant are the stabilization of body temperature by maintaining a neutral thermal environment, the maintenance of respiration, the prevention of infection, the provision of adequate nutrition and hydration, and the conservation of energy. Important functions of the nurse are to involve the parents in the care of the infant, to explain therapeutic procedures, and to facilitate attachment between the infant and family. Also called preemie, preterm infant. Compare postmature infant.
