Longitudinal follow-up of a cohort of 350 singleton infants born at less than 32 weeks of amenorrhea: neurocognitive screening, academic outcome, and perinatal factors

Objective: To analyse the incidence of neurodevelopmental disorders at the age 6-10 years, in children born at less than 32 weeks of amenorrhea, and to identify the perinatal and neonatal factors associated with adverse neurodevelopmental outcomes at this age.

Study design: Longitudinal prospective trial in a French university and tertiary perinatal care centre. A total of 350 preterm singletons born in hospital at less than 32 weeks of amenorrhea between 1997 and 2001 were included. Children were invited for examination to screen for neurocognitive disorders between 4 and 8 years of age and re-contacted when they were between 6 and 10 years of age to evaluate school results. Three profiles of neurocognitive outcome were defined (normal, minor disorder, or major disorder) and correlated with maternal, antenatal, perinatal, and neonatal factors.

Results: The survival rate of our cohort was 80.8% (283/350) and the proportion of survivors followed-up was 71.4% (202/283). There were 137 children (68%) with normal profiles, 29 (14%) with minor disorders, and 36 (18%) with major disorders. For those born at less than 28 weeks of amenorrhea, the survival rate was 62.7% (64/102) and the proportion of survivors followed-up was 78.1% (50/64). Among these children, 24 (48.0%) had normal outcomes, 8 (16.0%) suffered from minor disorders, and 18 (36.0%) had major disorders. The three principal independent risk factors for major or minor disorders at school age were gestational age less than 28 weeks of amenorrhea (adjusted odds ratio: 1.28 [95% confidence interval: 1.06-1.56]), chronic lung disease at birth (adjusted odds ratio: 2.92 [95% confidence interval: 1.15-7.42]), and an abnormal electroencephalogram before discharge (adjusted odds ratio: 2.61 [95% confidence interval: 1.10-6.18]). Moreover, abnormal brain ultrasonography was identified as an independent risk factor for occurrence of major disorders (adjusted odds ratio: 2.98 [95% confidence interval: 1.31-6.71]).

Conclusion: Very preterm infants remain at high risk for long-term neurodevelopmental disorders. Several neonatal factors, particularly chronic lung disease, seem to be important determinants of long-term outcome.