A national two year follow up study of extremely low birthweight infants born in 1996-1997

Abstract

Objective: To study neurodevelopmental outcome in a two year cohort of extremely low birthweight (ELBW) infants at 18 months corrected age, to compare the development of the ELBW infant subcohort with that of control children, and to find risk factors associated with unfavourable outcome.

Study design: All 211 surviving ELBW infants (birth weight < 1000 g) born in Finland in 1996-1997 were included in a national survey. The ELBW infants (n = 78) who were born and followed in Helsinki University Hospital belonged to a regional subcohort and were compared with a control group of 75 full term infants. A national follow up programme included neurological, speech, vision, and hearing assessments at 18 months of corrected age. Bayley infant scale assessment was performed on the subcohort and their controls at 24 months of age. Risk factors for unfavourable outcome were estimated using logistic and linear regression models.

Results: The prevalence of cerebral palsy was 11%, of all motor impairments 24%, of ophthalmic abnormalities 23%, and of speech delay 42%. No impairment was found in 42% of children, and 18% were classified as severely impaired. The prevalence of ophthalmic abnormalities decreased with increasing birth weight and gestational age, but the prevalence of other impairments did not. In the subcohort, a positive correlation was found between the date of birth and Bayley scores.

Conclusion: Ophthalmic abnormalities decreased with increasing birth weight and gestational age, but no other outcome differences were found between birthweight groups or in surviving ELBW infants born at 22-26 weeks gestation. The prognosis in the regional subcohort seemed to improve during the short study period, but this needs to be confirmed.

Figure 1

Prevalence of (A) motor impairment, (B) delay in speech development, and (C) abnormalities in ophthalmic assessment at the corrected age of 18 months in different birthweight groups.

Figure 2

Stillbirth rate, two year mortality rate, prevalence of severe impairments, mild impairments, and normal development, and missing developmental data in extremely low birthweight infants born at 22–26 gestational weeks. Severe impairment was defined as cerebral palsy, blindness, hearing impairment necessitating hearing aid, seizures, or a combination of three or more milder impairments detected in the ophthalmic, hearing, motor, or speech assessment.