Distributions of birth weight in seven Dublin maternity units.

Differences in birthweight distribution among babies born to Dublin residents during one year in seven maternity units were analysed. Large differences were found between the hospitals. The evidence indicated that most of the difference was attributable to the differing socioeconomic profile of the mothers in the hospitals. The socioeconomic gradients shown by the hospitals in the proportions of babies weighing less than or equal to 2500 g, less than or equal to 3000 g, and 3001-4499 g diverged with increasing socioeconomic disadvantage. Steepest gradients were found in hospitals where the socioeconomic disadvantage was greatest, and vice versa. The differences between the hospitals in the socioeconomic gradient of birthweight performance were tentatively ascribed to some sort of catchment area effect, which added to the disadvantage of the already most disadvantaged mothers. Differences in antenatal care and induction of labour between hospitals were not assessed but were thought unlikely to have made a major contribution to the differences in socioeconomic gradient.