Recent changes in delivery site of low-birth-weight infants in Washington: Impact on birth weight-specific mortality

OBJECTIVES: Our purpose was to ascertain whether the proportion of low-birth-weight infants delivered in Washington at tertiary hospitals changed between 1980 and 1991 and whether mortality differed by level of birth hospital. STUDY DESIGN: A retrospective cohort study was performed of 500 to 2499 gm infants both to Washington residents between 1980 and 1991 (n = 43,228). RESULTS: Overall, the percentage of low-birth-weight infants born at tertiary centers rose from 1980 to 1982 through 1986 to 1988 and subsequently declined significantly. Among infants weighing <2000 gm nontertiary delivery was associated with greater potentially preventable mortality (500 to 999 gm, relative risk 1.5, 95% confidence interval 1.3 to 1.8; 1000 to 1499 gm, relative risk 2.1, 95% confidence interval 1.3 to 3.3; 1500 to 1999 gm, relative risk 1.6, 95% confidence interval 1.0 to 2.6). Nontertiary delivery of 2000 to 2499 gm infants was associated with lower overall mortality (relative risk 0.5, 95% confidence interval 0.3 to 0.8), but higher-risk deliveries in this birth weight range were apparently concentrated at tertiary hospitals. CONCLUSIONS: In light of the apparent benefit of tertiary center birth for infants weighing <2000 gm, the possible erosion of effective regionalized perinatal care networks should be monitored closely.