Print: Chapter 36. Preterm Birth

Preterm Birth: Introduction Low birthweight defines neonates who are born too small, and preterm or premature birth are the terms used to define neonates who are born too early. With respect to gestational age, a newborn may be preterm, term, or postterm. With respect to size, a newborn may be normally grown or appropriate for gestational age, small in size or small-for-gestational age, or overgrown and consequently large-for-gestational age. In recent years, the term small-for-gestational age has been widely used to categorize newborns whose birthweight is usually below the 10th percentile for gestational age. Other frequently used terms have included fetal growth restriction or intrauterine growth restriction. The term large-for-gestational age has been widely used to categorize newborns whose birthweight is above the 90th percentile for gestational age, and the term appropriate-for-gestational age designates newborns whose weight is between the 10th and 90th percentiles. Thus, infants born before term can be smallor large-for-gestational age but still fit the definition of preterm.