Gestational age-dependent risk patterns in small for gestational age preterm infants: a large multivariable cohort study.

BACKGROUND: Small for gestational age (SGA) preterm infants remain at high risk for morbidity and mortality, yet the influence of gestational age (GA) on these outcomes is not fully understood. METHODS: The influence of gestational age on morbidity and mortality in SGA preterm infants (23-34 weeks) was analyzed in a cohort of 11,208 preterm infants. Infants were divided into three groups according to gestational age (23-27 weeks, 28-31 weeks, and 32-34 weeks). RESULTS: Compared with non-SGA infants of the same gestational age group, SGA infants showed higher rates of fetal distress and Apgar score ≤5 at any gestational age. Hyaline membrane disease increased between 23 and 27 weeks but decreased between 32 and 34 weeks, whereas intraventricular hemorrhage showed the opposite trend. Pneumothorax and periventricular leukomalacia increased mainly between 23 and 27 weeks, while necrotizing enterocolitis, sepsis, and gastrointestinal perforation increased between 28 and 31 weeks. Mortality was higher between 23 and 31 weeks. In survivors, moderate-severe bronchopulmonary dysplasia increased between 23 and 31 weeks, and retinopathy of prematurity increased after 28 weeks. Gestational age appeared to modify the associations between SGA status and selected neonatal outcomes, including hyaline membrane disease, intraventricular hemorrhage, and mortality. CONCLUSIONS: Gestational age may influence the pattern of associated morbidities among SGA preterm infants born at 23 to 34 weeks of gestation. In these newborns, the risk of mortality was increased 3.13-fold.