A systematic review of severe morbidity in infants born late preterm

Abstract

OBJECTIVE Late-preterm infants (34 weeks 0/7 days-36 weeks 6/7 days' gestation) represent the largest proportion of singleton preterm births. A systematic review was performed to access the short- and/or long-term morbidity of late-preterm infants. STUDY DESIGN An electronic search was conducted for cohort studies published from January 2000 through July 2010. RESULTS We identified 22 studies studying 29,375,675 infants. Compared with infants born at term, infants born late preterm were more likely to suffer poorer short-term outcomes such as respiratory distress syndrome (relative risk [RR], 17.3), intraventricular hemorrhage (RR, 4.9), and death <28 days (RR, 5.9). Beyond the neonatal period, late-preterm infants were more likely to die in the first year (RR, 3.7) and to suffer from cerebral palsy (RR, 3.1). CONCLUSION Although the absolute incidence of neonatal mortality and morbidity in infants born late preterm is low, its incidence is significantly increased as compared with infants born at term. The incidence of preterm birth, defined as delivery before the end of the 37th week (259th day) of pregnancy from the first day of the last menstrual period, is increasing. In the United States, the preterm rate rose from 9.1% in 1981 to 12.3% in 2003. 1 In certain regions in Brazil the prevalence of preterm birth was 15% according to the 2004 Pelotas birth cohort, roughly 3 times the prevalence found in the 1982 birth cohort in the same city.