Birth weight less than 800 grams: changing outcomes and influences of gender and gestation number.

Mortality and neurodevelopmental morbidity were compared in two cohorts of neonates with birth weights of less than 800 g. The neonates, born in the years 1977 through 1980 (original cohort) and 1983 through 1985 (current cohort), were patients in the same university intensive care nursery. Mortality was 80% in the original cohort and 64% in the current cohort (P = .01). In the current cohort, survival was significantly better for neonates with birth weights of more than 749 g (58% vs 27%; P = .001). Survival was also significantly associated with gender and with gestation number (female survival was 48% and male survival was 23%, P = .003; singleton survival was 41% and twin survival was 21%, P = .03). Prevalence of major central nervous system handicaps did not significantly differ between the two study groups, but severity of handicap was worse for the current study group. Morbidity in the current cohort was most severe for twins (67% with a major central nervous system handicap) and was least severe for singleton girls (4% with a major central nervous system handicap, P = .002). Delivery mode appeared to affect outcome. Although there were more nursery admissions and more survivors among neonates with birth weights of less than 800 g during the period 1983 through 1985 compared with the period 1977 through 1980, overall neurodevelopmental morbidity worsened.