Data for this study were obtained from the computerized Atlee Perinatal Database during the period January 1, 1986, to December 31, 1993. Data collection was jointly initiated by the departments of Obstetrics and Gynecology and Neonatal Pediatrics at Dalhousie University in Halifax; the Grace Maternity Hospital; and the Nova Scotia Department of Health, Canada. The province of Nova Scotia has a long-standing system of regionalized reproductive health care. Data from the two tertiary care hospitals (6,000 pregnancies per year) and the seven regional care hospitals (4,000 pregnancies per year) were available from 1986 onwards, while the remaining 17 community hospitals (2,000-3,000 pregnancies per year) were initiated into the program in 1988. Estimated coverage in the province was 80 percent between 1986 and 1987, and it rose to 100 percent for the period 1988-1993(Atlee Perinatal Database Committee, unpublished data, 1993).