Neurodevelopmental Outcome at 5 Years of Age of a National Cohort of Extremely Low Birth Weight Infants Who Were Born in 1996–1997

Abstract

Increasing survival of extremely low birth weight (ELBW; birth weight < 1000 g) infants raises a concern regarding the risks of adverse long-term outcome such as cognitive dysfunction. Few studies have reported long-term follow-up of representative regional cohorts. The objective of this study was to assess the 5-year outcome of a prospectively followed national ELBW infant cohort. Of all live-born ELBW infants (n = 351) who were delivered in the 2-year period 1996-1997 in Finland, 206 (59%) survived until the age of 5 years. Of these, 103 were born at < 27 gestational weeks (GW). A total of 172 children were assessed with neurocognitive tests (Wechsler Preschool and Primary Scale of Intelligence-Revised and a Developmental Neuropsychological Assessment [NEPSY]). Nine children with cognitive impairment and inability to cooperate in testing were not assessed. Motor development was assessed with a modified Touwen test. The rate of cognitive impairment in the ELBW survivors was 9%. The rate of cerebral palsy was 14% (19% of ELBW infants who were born at < 27 GW). The mean full-scale IQ of the assessed children was 96 +/- 19 and in children of GW < 27 was 94 +/- 19. Attention, language, sensorimotor, visuospatial, and verbal memory values of NEPSY assessment were significantly poorer compared with normal population means. Four percent needed a hearing aid, and 30% had ophthalmic findings. Of 21 children who had been treated with laser/cryo for retinopathy of prematurity, 17 (81%) had abnormal ophthalmic findings. Of the whole cohort, 41 (20%) exhibited major disabilities, 38 (19%) exhibited minor disabilities, and 124 (61%) showed development with no functional abnormalities but subtle departures from the norm. Only 53 (26%) of the total ELBW infant cohort were classified to have normal outcome excluding any abnormal ophthalmic, auditory, neurologic, or developmental findings. Being small for gestational age at birth was associated with suboptimal growth at least until age 5. Only one fourth of the ELBW infants were classified as normally developed at age 5. The high rate of cognitive dysfunction suggests an increased risk for learning difficulties that needs to be evaluated at a later age. Extended follow-up should be the rule in outcome studies of ELBW infant cohorts to elucidate the impact of immaturity on school achievement and social behavior later in life.