Trends in mortality and cerebral palsy in a geographically based cohort of very low birth weight neonates born between 1982 to 1994

Abstract

Objective: To analyze whether the increasing survival of very low birth weight infants during the 1980s and 1990s has increased the risk of cerebral palsy among survivors.

Methods: The study cohort consisted of 2076 consecutively born infants, with birth weights of 500 to 1500 g and no major anomaly, born July 1, 1982, through June 30, 1994, to residents of a 17-county region in North Carolina. These infants had a mean birth weight of 1096 g (standard deviation, 251 g) and a mean gestational age of 29 weeks (standard deviation, 3 weeks). One thousand five hundred sixty-eight infants (76%) survived to 1 year adjusted age, at which point 1282 infants (82%) were examined at our medical center. The diagnosis of cerebral palsy was made only if the examining pediatrician and a pediatric physical therapist agreed on the diagnosis. To analyze trends across time, the Cochran-Armitage chi2 test and logistic regression were applied to data for infants categorized into six 2-year epochs according to year of birth.

Results: Mortality did not change significantly through 1990, and then began to decrease in 1990 to 1994. During the study period, mortality decreased from 36.8% between 1982 and 1984, to 13.8% between 1992 and 1994. The prevalence of cerebral palsy among survivors was constant from 1982 to 1988 (11.3%), decreased slightly from 1988 to 1990 (9.2%), and was lowest in 1990 to 1994 (5.2%). These secular trends in mortality and cerebral palsy risk remained significant when adjusted for gestational age, gender, and race. When adjusted for surfactant use, the trend in mortality was no longer significant, whereas the trend in cerebral palsy risk persisted.

Conclusions: The increasing survival of very low birth weight infants in the 1980s and 1990s has not resulted in an increased prevalence of cerebral palsy among survivors.