Risk factors for neonatal death in twin gestations in the state of South Carolina

OBJECTIVE: The aim of the study was to describe risk factors for neonatal d eath among twins born in South Carolina. STUDY DESIGN: South Carolina publicly accessible live birth and infant deat h cohort files for live-born twins >500 g were reviewed for the years 1988 through 1993. Infants with lethal anomalies were deleted from the cohort be fore analysis. Risk factors for neonatal death were determined for the enti re cohort and for the birth weight categories of 500 to 999 g, 1000 to 1499 g, 1500 to 2499 g, and greater than or equal to 2500 g. Statistical compar isons were performed with the Mantel-Haenszel chi(2) test and multivariate logistic regression. RESULTS: Of 7833 live-born twins, 263 (3.4%) died during the neonatal perio d. The mean birth weight was 2357 +/- 650 g (range 500-5358 g) at a mean ge stational age of 35.7 +/- 3.5 weeks. Overall neonatal mortality rates were significantly increased (P < .001) for twins whose mothers were nonwhite (4 .2 vs 2.8%), were <20 years old (6.0 vs 3.2%), or received no prenatal care (14.7 vs 3.1%). After we controlled for population characteristics with mu ltivariate techniques, analysis revealed birth weight <2500 g and residence in the most populous urban areas to be associated with increased neonatal mortality rates. After stratification into birth weight categories, race wa s no longer a significant variable; in fact, nonwhite twins had a survival advantage at birth weights <1500 g, but this was not significant. Maternal age <20 years was associated with a higher neonatal mortality rate for infa nts with birth weights between 1500 and 2499 g. Absence of prenatal care si gnificantly increased the neonatal mortality rate for twins' greater than o r equal to 1500 g but not for those who were smaller. For infants weighing 500 to 999 g neonatal mortality rates were significantly lower at hospitals with greater than or equal to 2000 deliveries/y than at hospitals with low er delivery volumes (P = .005). CONCLUSIONS: Although the overall neonatal mortality rate for twins continu es to improve, increased rates are still seen among blacks, teenagers, and women who receive no prenatal care. Twins between 500 and 999 g have signif icantly reduced neonatal mortality rates when delivered at hospitals with a high obstetric volume.