Outcome of Extremely Low Birth Weight Infants (500 to 999 Grams) over a 12-year Period

Objective: Advances in neonatology have contributed to improved survival for extremely low birth weight (ELBW) infants. Neurodevelopmental outcome is usually reported for a single large group of infants rather than according to smaller birth weight groups because of small numbers. Our purpose was to review the neurodevelopmental outcome of a large group of ELBW infants and examine differential outcome according to birth weight.

Study Design: A total of 446 infants born between 1979 and 1991, with a birth weight of 500 to 999 g, were followed to mean age 55 months +/- 33 standard deviation. Univariate analyses of medical risk factors of birth weight, gestational age, year of birth, growth retardation, gender, inborn/outborn status, days on oxygen, intracranial hemorrhage, and social risk in relation to outcome were conducted on the group as a whole. Neurologic/developmental outcome was also analyzed by 100-g weight groups.

Results: A total of 61% of all infants were completely normal, with no neurologic, neurosensory, or cognitive deficits. There was no association between outcome and birth weight. There was a strong association between intracranial hemorrhage (ICH) grade III or IV and/or cystic periventricular leukomalacia (PVL) and abnormal outcome (Somers' D = .17) and ICH III/IV and/or cystic PVL and cognitive outcome (Kendall's tau = .15). Mild to moderate cognitive delays were associated with chronic lung disease (oxygen >60 days) (Kruskal-Wallis chi2 = 17.53) or high social risk (Kruskal-Wallis chi2 = 22.17).

Conclusion: In this study of ELBW infants, low birth weight was not associated with abnormal outcome. The risk factors of ICH III-IV/cystic PVL, chronic lung disease, and high social risk were associated with abnormal outcome.