Neurodevelopmental outcome in extremely low birth weight infants: what is the minimum age for reliable developmental prognosis?

Aim: We present a longitudinal study on the neurodevelopmental outcome in preterm infants with extremely low birth weight <1000 g (ELBW) to answer the question at which age a developmental prognosis can be given.

Methods: A group of 129 ELBW, median birth weight: 794 g (SD 123 g), gestational age: 27.0 weeks (SD 2.0 weeks), born between 1993 and 1998, were followed up to the age between 6 and 10 years (mean 8.5 years [SD 1.7 years]) and evaluated by neurodevelopmental and psychometric tests. The status of children without cerebral palsy was ranked into categories of major, minor and no developmental impairments.

Results: At the time of the last follow-up examination 17% of the children showed a major impairment including 9% cerebral palsy, 42% a minor impairment and 41% were normally developed. The longitudinal analysis of cases without cerebral palsy reveals that an assessment 'at term' can only give the correct developmental prognosis in 49% of the cases. At the corrected age of 12 months the prognosis is correct in 59% of the cases, whereas at the corrected age of 3 years 70% proves to be right. Diagnosis of cerebral palsy could be confirmed at the corrected age of 2 years with sufficient reliability.

Conclusion: The neurodevelopmental evaluation of former preterm infants with a birth weight <1000 g demands a follow-up period of at least 6 years in order to make reliable statements. We are doubtful that follow-up testing completed prior to this age can yield reliable results.