Premature Birth

Abstract

Definitions of premature birth vary. A definition of prematurity in which birth weight is less than 5.5 lb could include low birth weight, but not premature (in weeks of age). Definitions based on a gestational age of less than 39 weeks might not be accurate. It is relatively clear that morality rates are closely related to gestational age. For example, the mortality rate in a group of infants weighing between 2.2 and 3.3 lb was about 50%, and in infants less than 30 weeks, the mortality rate was 63%. Approximately, two thirds of all newborn mortality is linked to premature birth. The incidence of premature birth in the USA is 7%.