Term Pregnancy A Period of Heterogeneous Risk for Infant Mortality

OBJECTIVE: To estimate the trend of maternal racial and ethnic differences in mortality for early-term (37 0/7 to 38 6/7 weeks of gestation) compared with full-term births (39 0/7 to 41 6/7 weeks of gestation). METHODS: We analyzed 46,329,018 singleton live births using the National Center for Health Statistics U.S. period-linked birth and infant death data from 1995 to 2006. Infant mortality rates, neonatal mortality rates, and post-neonatal mortality rates were calculated according to gestational age, race and ethnicity, and cause of death. RESULTS: Overall, infant mortality rates have decreased for early-term and full-term births between 1995 and 2006. At 37 weeks of gestation, Hispanics had the greatest decline in infant mortality rates (35.4%; 4.8 per 1,000 to 3.1 per 1,000) followed by 22.4% for whites (4.9 per 1,000 to 3.8 per 1,000); blacks had the smallest decline (6.8%; 5.9 per 1,000 to 5.5 per 1,000) as a result of a stagnant neonatal mortality rate. At 37 weeks compared with 40 weeks of gestation, neonatal mortality rates increase. For Hispanics, the relative risk is 2.6 (95% confidence interval [CI] 2.0-3.3); for whites, the relative risk is 2.6 (95% CI 2.2-3.1); and for blacks, the relative risk is 2.9 (95% CI 2.2-3.8). Neonatal mortality rates are still increased at 38 weeks of gestation. At both early-and full-term gestations, neonatal mortality rates for blacks are 40% higher than for whites and post-neonatal mortality rates 80% higher, whereas Hispanics have a reduced post-neonatal mortality rate when compared with whites. CONCLUSION: Early-term births are associated with higher neonatal, postneonatal, and infant mortality rates compared with full-term births with concerning racial and ethnic disparity in rates and trends. (Obstet Gynecol 2011;117:1279-87) DOI: 10.1097/AOG.0b013e3182179e28