Population-Based Study of the Incidence, Complexity, and Severity of Neurologic Disability Among Survivors Weighing 500 through 1250 Grams at Birth: A Comparison of Two Birth Cohorts

¹ From the Department of Pediatrics and Department of Pediatrics, Royal Alexandra Hospital, Edmonton, Canada
² From the Medical School, University of Alberta, Royal Alexandra Hospital, Edmonton, Canada
³ From the Research Office, Glenrose Rehabilitation Hospital, Royal Alexandra Hospital, Edmonton, Canada

Mortality and incidence, complexity, and severity of early childhood neurodevelopmental disability are reported for two cohorts of preterm infants of 500 through 1250 g birth weight. Comparing 1978-1979 (cohort 1) and 1988-1989 (cohort 2), 1-year survival improved from 82 (36%) of 226 to 197 (67%) of 291. Cohort 1 survivors were heavier and more mature than cohort 2 survivors (1047 g vs 930 g, 29.6 vs 27.3 weeks). Parental demographic variables were similar. The incidence of specific disabilities with greater than 97% follow-up to 1.5 years adjusted age did not change: cerebral palsy, 14 (17%) vs 20 (10%); vision loss, 5 (6%) vs 9 (5%); mental retardation, 9 (11%) vs 13 (7%); hearing loss, 3 (4%) vs 7 (4%); and convulsive disorders, 2 (2%) vs 3 (2%). The overall number of disabled children (17 [21%] vs 30 [15%]), complexity of disability (2 disabilities per child: 11 [13%] vs 10 [5%]), and severity of disability (projected dependency: 6 [7%] vs 10 [5%]) did not differ between cohorts 1 and 2. The cerebral palsy prevalence, based on neonatal survival, dropped from 157 per 1000 to 93 per 1000. Analysis by birth weight-specific categories in 250 g increments did not alter results, but disability rates were highest for those of lowest weight. In contrast to other reports this population-based North American study from a well-developed perinatal regional program reports no increase in incidence, complexity, or severity of disability in preterm infants weighing 500 through 1250 g at birth.

Key Words: very low birth weight • cerebral palsy • neurodevelopmental disability

Submitted on March 25, 1992
Accepted on June 29, 1992

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