Multiple deliveries in North Carolina: effects on birth outcomes

The purpose of this study is to examine the trends in multiple deliveries in North Carolina and assess their effect on the rates of low birth weight, fetal mortality, and infant mortality. Using North Carolina vital statistics files, trends in multiple births, categorized by race, maternal age, and birth weight, were examined for the period 1980-1997. A partitioning method was used to estimate the contribution of maternal age distribution and age-specific multiple birth rates to the overall increase in multiple births, and the contribution of the changing multiple birth rate to observed trends in low birth weight and fetal and infant mortality. Between 1980 and 1997, the state's multiple birth rate increased by 40%. Most of the increase was due to a rise in the age-specific multiple birth rates, rather than a shift in the maternal age distribution. The increase in the multiple birth rate accounted for a substantial proportion of the increase in low birth weight among Whites and Blacks. The rise in multiple births also hindered further declines in fetal and infant mortality during this time. Multiple births are an increasingly important contributor to perinatal outcomes, and warrant greater consideration in research aimed at evaluating trends in low birth weight and infant mortality.