This multicenter network compared prospective data from 617 infants with birthweight < 1501g or gestational age < 31 weeks between January 1, 1996 through December 1997, from 6 Pacific Rim nurseries. Data collected included gestational age (GA), birthweight (BW), Apgar scores, blood gas and head ultrasound results, survival to nursery discharge, use of antenatal steroids (AS), delivery route, and surfactant use. Severity of illness scores were derived from data obtained during the first 12 hours of life, using Critical Risk Index for Babies (CRIB scores). The association between risk factors (CRIB scores, GA and BW) and mortality were studied.

Results: GA and BW of the infants were similar in all nurseries, while CRIB scores were significantly higher and the 5 minute Apgar scores were lower at the San Francisco nursery. The overall mortality was similar at all centers (7-17% range), while the incidence of intracranial hemorrhage varied between 5-28%. The Tokyo center had the highest GA and BW-specific survival, as well as the lowest incidence of significant intracranial hemorrhage(defined as >Grade II) despite also having the lowest use of AS (5% of births, p<0.05) as well as surfactant use (26% of VLBW infants). Using linear regression, CRIB scores (r=0.56), BW (r=0.42), and GA (r=0.4) were all significantly correlated with mortality. In a multiple logistic regression model, only CRIB score remained a significant predictor of death (p<0.001). Summary: There are differences in GA and BW-specific survival among these nurseries that do not correlate with variation in the clinical practices studied. Improved survival outcome in the Tokyo center may be related to improved obstetric and/or neonatal care, acceleration of neonatal maturity, improved maternal nutrition, or the more intangible effects of a higher level of socio-economic status of the women.