The Respiratory Distress Syndrome of the Newborn: Immaturity versus Prematurity.

The respiratory distress syndrome (RDS) remains the most important cause of morbidity and mortality among anatomically normal infants during the first few days of life. There is no general agreement as to the aetiology or pathogenesis of this condition. However, its association with a number of maternal and foetal factors is well recognized; foremost among these is prematurity. While the definition of the premature infant is based on low birth weight (5 lb. 8 oz. (2 5 kg.) or less), the term is often used loosely to denote immaturity. This may lead to confusion, for immature infants may be heavier than the average full-term baby. At the same time, about one-third of all 'premature' infants born in this country have had a gestation of 38 weeks or more (Butler and Bonham, 1963). In this paper, a study has been made of the relative importance of birth weight and length of gestation on the incidence of RDS and its mortality.