prematurity
(prē‵mă-chur'ĭt-ē, -tur', -tūr'' 
)
The state of an infant born any time before completion of the 37th week of gestation. The normal gestation period for humans is 40 weeks. Because of the difficulty of obtaining accurate and objective data on the exact length of gestation, a birth weight of 2500 g (5.5 lb) or less has been accepted internationally as the clinical criterion of prematurity regardless of the period of gestation. Other measures suggestive of prematurity are crown-heel length (47 cm or less), crown-rump length (32 cm or less), occipitofrontal circumference (33 cm or less), occipitofrontal diameter (11.5 cm or less), and ratio of the thorax circumference to the head circumference (less than 93%).
The use of a single-criterion measure (birth weight) imposes limitations in accurately identifying those infants born before adequate development of body organs and systems has been achieved. It can easily include mature infants who are of low birth weight for reasons other than a shortened gestation period. The Expert Committee on Prematurity of the World Health Organization (1961) recommended that the concept of prematurity in the international definition be replaced by that of low birth weight. Low birth weight more accurately describes infants weighing less than 2500 g at birth than does prematurity. The latter term should be reserved for those neonates within the low birth weight group with evidence of incomplete development.
In the U.S. approx. 7.1% of white liveborn and 13.4% of nonwhite liveborn infants weigh 2500 g or less. Chances of survival depend on the degree of maturity achieved, general medical condition, and quality of care received.
Prematurity is the leading cause of death in the neonatal period. Mortality among infants weighing less than 2500 g at birth is 17 times greater than among infants with birth weight above 2500 g. Chief causes of mortality are abnormal pulmonary ventilation, infection, intracranial hemorrhage, abnormal blood conditions, and congenital anomalies. Antenatal steroids assist fetal lung development.
Etiology: The incidence of neonates of low birth weight is more frequent among females, nonwhite races, plural births, and the first- and fifth-born (and more) infants. Delivery of infants of low birth weight is reported to be more frequent among women with one or more of the following characteristics: having their children at either a very young age or between ages 45 and 49; being unmarried; having children closely spaced (less than 2 to 4 years between births); and living in a large urban area.
Another factor associated with low birth weight is the socioeconomic status of the family as measured by the mother's educational attainment. The proportion of infants of low birth weight born to mothers with 16 years or more of education was half of that of infants born to mothers with less than 9 years of education. Low birth weight is also associated with generally elevated risk of infant mortality, congenital malformations, mental retardation, and other physical and neurological impairments.
Complications: Frequently, premature infants are hand icapped by a number of anatomical and physiological limitations. These limitations vary in direct proportion to the degree of immaturity present. Limitations include weakness of the sucking and swallowing reflexes, small capacity of stomach, impairment of renal function, incomplete development of capillaries of the lungs, immature alveoli of the lungs, weakness of the cough and gag reflexes, weakness of the thoracic cage muscles and other muscles used in respiration, inadequate regulation of body temperature, incomplete or poorly developed enzyme systems, hepatic immaturity, and deficient placental transfer and antenatal storage of minerals, vitamins, and immune compounds. Severely premature infants have high rates of neurological deficits later in life.
SEE: intrauterine growth retardation; premature rupture of membranes.
Patient Care: Ideally, the premature birth should take place in a regional intensive care center rather than a community health facility so that specially prepared staff are available to manage the birth and the premature infant, eliminating the need for infant transfer and mother-child separation. A resuscitation team should be in attendance to take immediate charge of the neonate. A physical assessment correlated with the expected maturation for fetal age is performed. Health care providers perform a neurological evaluation, obtain an Apgar score, ensure proper environmental temperature, provide proper fluid and caloric intake, ensure parental bonding and support, assess laboratory reports, monitor intake and output, notify the pediatrician and nursery of the (impending) premature birth, weigh the infant daily at the same time without clothing and on the same scale, monitor oxygen concentration at frequent intervals, hold and cuddle the infant during feedings, cover the infant when removing from isolette, and provide adequate time for feeding.
Care of low-birth-weight infants: Care of low-birth-weight infants should be individualized and reflect the needs of the developing infant with regard to anatomical and physiological hand icaps. Evaluation for degree of immaturity and identification of special problems after birth dictates care required by these infants. In general, care centers on prevention of infection, stabilization of body temperature, maintenance of respiration, and provision of adequate nutrition and hydration.
Aseptic technique is required. An incubator or heated bed provides a suitable environment for maintenance of body temperature. A high-humidity environment may be of value for infants with respiratory difficulties. Gentle nasal and pharyngeal suctioning aids in keeping airways clear. Use of oxygen should be restricted to the minimal amounts required for survival of the infant. Because of the danger of retrolental fibroplasia, the oxygen concentration should not exceed 30%.
Depending on the infant's sucking and swallowing abilities, feeding by gavage may be necessary. Some infants may not be given anything by mouth for as long as 72 hr after birth. Caloric and fluid intakes are increased gradually until 100 to 120 cal/kg and 140 to 150 mL/kg, respectively, in 24 hr are reached. The time required to achieve these intake levels depends on the newborn's condition. The infant may require small, frequent feedings to cope with the small capacity of the stomach, to prevent vomiting and distention, and to meet the body's caloric and fluid requirements. Overfeeding should be avoided. During the early days of life, clyses are sometimes administered to maintain adequate hydration. Breast milk is the optimal nutritional choice.
The infant should not be allowed to become fatigued from excessive hand ling, prolonged feeding procedures, or too much crying. Body position should be changed every 2 to 4 hr. Gentle hand ling should be practiced. The newborn and infant should receive cuddling and pleasant vocal stimulation several times a day.
Because of the possibility of retinal damage, premature infants should not be exposed to bright light. Parents are kept informed of their infant’s condition, and equipment, procedures, and treatments used are explained. They are encouraged to visit, stroke and touch, and then hold and feed the neonate as this becomes possible. Home health care may be required to assist the parents in caring for special needs when the neonate is ready for discharge.