The risks of adverse neonatal outcome among preterm small for gestational age infants according to neonatal versus fetal growth standards

Objective. To evaluate neonatal and fetal growth standards in determining the impact of small for gestational age (SGA) on neonatal mortality and morbidity. Design. A hospital-based cohort study of infants born in a regional tertiary care center and admitted to the neonatal intensive care unit. Setting and Participants. A total of 1267 singleton neonates of < 34 weeks gestational age, without any congenital anomalies, born between January 1, 1993 and December 31, 2001. Outcome Measures. Each outcome variable including mortality, respiratory distress syndrome, bronchopulmonary dysplasia, intraventricular hemorrhage (IVH), periventricular leukomalacia, and necrotizing enterocolitis was related to growth status as defined by fetal and neonatal growth standards after adjustment for potential confounders. Results. The number of SGA infants was 11.6% (n = 147) of the study population according to neonatal growth standards, but it was increased to 23.3% ( n = 295) when fetal growth standards were used. According to fetal growth standards, when SGA was compared with appropriate for gestational age infants, it was associated with an increased risk of respiratory distress syndrome ( odds ratio [ OR] 1.40; 95% confidence interval [CI] 1.00-1.95), bronchopulmonary dysplasia (OR 2.18; 95% CI 1.33 - 3.59), IVH ( OR 1.67; 95% CI 1.13 - 2.45), and retinopathy of prematurity ( OR 3.88; 95% CI 2.33 - 6.48). However, only neonatal mortality ( OR 3.64; 95% CI 1.64 - 8.09), retinopathy of prematurity ( OR 5.38; 95% CI 2.87 - 10.90), and necrotizing enterocolitis ( OR 2.47; 95% CI 1.21 - 5.07) were positively associated with SGA when using neonatal growth standards. Conclusions. Compared with the neonatal growth standards, the fetal growth standards are better in identifying increased risk of respiratory morbidity and IVH among preterm SGA infants.