Intellectual outcomes of extremely preterm infants at school age

Abstract

Background: The survival rate of extremely preterm (EP) infants (<28 weeks of gestation) has improved dramatically, and there is great interest in the long-term prognosis. The aim of this study was to elucidate the influence of prenatal and postnatal care on long-term intellectual outcome in EP infants.

Methods: Subjects were EP infants admitted to the neonatal intensive care unit from 1982 to 2005. The survival rate and neurodevelopmental outcomes at 6 years of age were analyzed for the periods 1982-1991 (period 1) and 1992-2005 (period 2). Logistic regression analysis was performed to examine risk factors for intellectual impairment.

Results: Survival rate improved significantly from 84.5% (period 1) to 92.4% (period 2; P = 0.007). Follow-up data were obtained from 92 children in period 1 (69.7% of survivors) and from 245 in period 2 (72.3% of survivors). The incidence of intellectual impairment increased from 16.3% (period 1) to 31.0% (period 2). Significant factors associated with intellectual impairment were period 2 (OR, 3.53; P = 0.007), supplemental oxygen at 36 weeks' corrected age (OR, 2.22; P = 0.012), number of days in the hospital (OR, 1.01; P = 0.012), intraventricular hemorrhage (IVH; OR, 3.05; P = 0.024), and later tube-feeding commencement date (OR, 1.10; P = 0.032).

Conclusions: Despite an increase in survival rate, the rate of intellectual impairment increased in period 2. According to risk factor analysis, reducing the incidence of chronic lung disease and/or apnea, IVH, and nutritional deprivation is a key factor in improving the intellectual outcomes of EP infants.

Keywords: extremely preterm infant; follow-up study; outcome study; risk factor.