Developmental Outcomes of Late Preterm Infants From Infancy to Kindergarten.

OBJECTIVE To compare developmental outcomes of late preterm infants (34-36 weeks' gestation) with infants born at early term (37-38 weeks' gestation) and term (39-41 weeks' gestation), from infancy through kindergarten. METHODS Sample included 1000 late preterm, 1800 early term, and 3200 term infants ascertained from the Early Childhood Longitudinal Study, Birth Cohort. Direct assessments of development were performed at 9 and 24 months by using the Bayley Short Form-Research Edition T-scores and at preschool and kindergarten using the Early Childhood Longitudinal Study, Birth Cohort reading and mathematics θ scores. Maternal and infant characteristics were obtained from birth certificate data and parent questionnaires. After controlling for covariates, we compared mean developmental outcomes between late preterm and full-term groups in serial cross-sectional analyses at each timepoint using multilinear regression, with pairwise comparisons testing for group differences by gestational age categories. RESULTS With covariates controlled at all timepoints, at 9 months late preterm infants demonstrated less optimal developmental outcomes (T = 47.31) compared with infants born early term (T = 49.12) and term (T = 50.09) (P < .0001). This association was not seen at 24 months, (P = .66) but reemerged at preschool. Late preterm infants demonstrated less optimal scores in preschool reading (P = .0006), preschool mathematics (P = .0014), and kindergarten reading (P = .0007) compared with infants born at term gestation. CONCLUSIONS Although late preterm infants demonstrate comparable developmental outcomes to full-term infants (early term and full-term gestation) at 24 months, they demonstrate less optimal reading outcomes at preschool and kindergarten timepoints. Ongoing developmental surveillance for late preterm infants is warranted into preschool and kindergarten.