Admissions and Emergency Visits by Late Preterm Singletons and Twins in the First 5 Years: A Population-Based Cohort Study

OBJECTIVE: To compare admission and emergency visits of late preterm (34^0/7-36^6/7 weeks) versus term infants (37^0/7-41^6/7 weeks) in the first 5 years. STUDY DESIGN: This population-based cohort study included all singletons and twins born alive at 34^0/7 to 41^6/7 weeks' gestation registered in a health administrative database in Ontario, Canada, between April 1, 2002 and December 31, 2012. Admissions and emergency visits from initial postnatal discharge to 5 years were compared between late preterm and term infants adjusting for maternal and infant characteristics. RESULTS: A total of 1,316,931 infants (75,364 late preterm infants) were included. Late preterm infants had more frequent admissions than term infants in the first 5 years in both singletons (adjusted incidence rate ratio [95% confidence interval] = 1.46 [1.42-1.49]) and twins (1.21 [1.11-1.31]). The difference in admissions between late preterm and term infants were smaller in twins than singletons and decreased with children's ages. Twins had less frequent admissions than singletons for late preterm infants, but not for term infants. The emergency visits were more frequent in late preterm than term infants in all the periods. CONCLUSION: Admissions and emergency visits were more frequent in late preterm than term infants through the first 5 years. Admissions were less frequent in late preterm twins than singletons.