Prediction and Prevention of Preterm Birth

Spontaneous preterm birth includes birth that follows preterm labor, preterm spontaneous rupture of membranes, and cervical insufficiency, but does not include indicated preterm delivery for maternal or fetal conditions (5). The preterm birth rate (birth at less than 37 completed weeks of gestation per 100 total births) increased more than 20% from 1990 to 2006. However, decreases in birth rates for both early preterm birth (earlier than 34 weeks of gestation) and late preterm birth (34 0/7–36 6/7 weeks of gestation) contributed to a decrease in the overall preterm birth rate between 2008 (12.3%) and 2009 (12.18%) (1). The risk of poor birth outcome generally decreases with advancing gestational age. Although risks are greatest for neonates born before 34 weeks of gestation, infants born after 34 weeks of gestation but before 37 weeks of gestation are still more likely to experience delivery complications, long-term impairment, and early death than those born later in pregnancy (6). Infants born prematurely have increased risks of mortality and morbidity throughout childhood, especially during the first year of life. In the absence of more comprehensive tests of fetal and neonatal status, gestational age is a common surrogate for presumed functional maturity. Although age is related to maturity, no easily identified gestational age boundary exists between a premature neonate and a mature neonate. The risks of perinatal, neonatal, and infant morbidity and mortality are lowest for infants born between 39 0/7 weeks of gestation and 40 6/7 weeks of gestation. These risks increase as gestational age at birth decreases, with morbidity reported at 37 weeks of gestation and even 38 weeks of gestation in some series (7, 8).