The impact of changes in preterm birth among twins on stillbirth and infant mortality in the United States.

Abstract

To examine trends for preterm births, stillbirths, neonatal and infant deaths in twin births by gestational age and birth weight categories, as well as trends in induction of labor and cesarean delivery during 1995-2006. A trend analysis was performed on data derived from the National Centers for Health Statistics' Vital Statistics Data files (1995-2006). The primary outcomes examined were preterm birth, stillbirth, neonatal and infant mortality. During the study period, rates of labor induction among twins decreased by 8% and rates of cesarean delivery increased by 35%. Concurrently, the preterm birth rate increased by 13% from 54% in 1995-96 to 61% in 2005-06. The overall stillbirth rate, and neonatal and infant death rates decreased during the same period by 21% (95% confidence interval (CI): 18-25%), 13% (95% CI: 9-16%) and 12% (95% CI: 8-15%), respectively. There were significant reductions in neonatal death rates related to respiratory distress syndrome (RDS; 48%, 95% CI: 41-54%) and congenital anomalies (25%, 95% CI: 16-33%) during the study period. Reductions in post-neonatal infant mortality were mainly in RDS (88%) and sudden infant death syndrome (26%). Mortality rates among infants born by either induction of labor or cesarean delivery fell during the study period and remained much lower than the overall infant mortality rate. The findings of this study suggest that during 1995-2006 there was an increase in preterm birth rates and a decrease in labor inductions with a sharp decline in stillbirth, neonatal and infant mortality rates.