Morbidity and Mortality in Small for Gestational Age Infants at 22 to 29 Weeks' Gestation

OBJECTIVES: To identify the relative risks of mortality and morbidities for small for gestational age (SGA) infants in comparison with non-SGA infants born at 22 to 29 weeks' gestation. METHODS: Data were collected (2006-2014) on 156 587 infants from 852 US centers participating in the Vermont Oxford Network. We defined SGA as sex-specific birth weight <10th centile for gestational age (GA) in days. Binomial generalized additive models with a thin plate spline term on GA by SGA were used to calculate the adjusted relative risks and 95% confidence intervals for outcomes by GA. RESULTS: Compared with non-SGA infants, the risk of patent ductus arteriosus decreased for SGA infants in early GA and then increased in later GA. SGA infants were also at increased risks of mortality, respiratory distress syndrome, necrotizing enterocolitis, late-onset sepsis, severe retinopathy of prematurity, and chronic lung disease. These risks of adverse outcomes, however, were not homogeneous across the GA range. Early-onset sepsis was not different between the 2 groups for the majority of GAs, although severe intraventricular hemorrhage was decreased among SGA infants for only gestational week 24 through week 25. CONCLUSIONS: SGA was associated with additional risks to mortality and morbidities, but the risks differed across the GA range.