Live births of infants less than 23 weeks gestation disproportionately affect infant mortality rates in the United States

Abstract

Objective: The aim of the study was to determine if states with high infant mortality rates (IMR) have more live births of infants < 23 weeks gestation than states with low IMR, and to determine if there are racial differences in births < 23 weeks in low and high IMR states. Study Design: Data were assessed using United States linked birth and death certificate data from 1997-2000. Ten states with the highest IMR over the 4-year study period were compared to 10 states with the lowest IMR. Statistical analysis was carried out by logistic regression. Results: After controlling for potential confounders, the odds of death from a birth < 23 weeks gestation were significantly higher in the states with the highest overall IMR. IMR was adjusted by removing live births < 23 weeks. African American infants < 23 weeks in high IMR states contributed to a greater percentage of IMR (25%) compared to African American infants in low IMR states (20%), or Caucasian infants in high IMR (15%), or low IMR (13%) states. Conclusions: States with high IMR are more likely to have live births of infants < 23 weeks gestation, compared to those states with low IMR. The contribution to the IMR from births < 23 weeks in high IMR states is disproportionately from African American infants.