Improvement of developmental outcome between 24 and 36 months corrected age in very preterm infants

Aim: To study early developmental course in preschool-aged very preterm infants and its association with perinatal risk factors and test-taking behaviour. Methods: Children born <30 weeks gestation and/or <1000 g in the Academic Medical Center of Amsterdam were assessed at 24 and 36 months corrected age with the Dutch Bayley Scales of Infant Development-II (BSID-II-NL) and neurological examination. Linear regression analyses for developmental change were performed with perinatal risk factors. Results: One hundred and forty-six children, mean GA 28 weeks and mean birth weight 1043 g, participated. Mental and psychomotor scores improved significantly with 6 and 7 points, respectively, from 24 to 36 months (p < 0.01). Mild to severe problems on at least one domain occurred less often at 36 (32%) compared to 24 months (63%) (p < 0.01), using corrected scores. Mental improvement was associated with being born very small for gestational age or < 28 weeks; psychomotor improvement was associated with not being treated with indomethacin. Difficult test behaviour occurred mostly at 24 months and was associated with non-optimal development at 36 months. Conclusion: Improved developmental outcome and test behaviour were found at 36 compared to 24 months in a cohort of very preterm children. Long-term outcome studies and retesting of behaviourally difficult children are recommended.