CDC, 2005i) (see also Figures 9-2 and 9-3 in Chapter 9 and Appendix B). The leading causes of infant mortality in the United States are preterm birth, low birth weight, and birth defects; so preterm birth and low birth weight are major contributors to infant mortality (Alexander et al., 2003; CDC, 2005i; Petrini et al., 2002). Dramatic declines in infant and neonatal mortality and gestational-age specific mortality over the last several decades have been attributed to improvements in obstetric and neonatal intensive care, especially for infants born preterm and small for gestational age (Allen et al., 2000; Alexander and Slay, 2002). However, the United States most recently had an increase in infant mortality from 6.8 to 7.0 per 1,000 live births in 2002 and an increase in the preterm birth rate to 12.3 percent in 2003 (CDC, 2005i) (see also Chapter 1 for discussion of mortality rates and variations in mortality by race and ethnicity).
Large variations in infant mortality rates exist among different geographical regions as well as among racial and ethnic groups (Alexander et al., 1999; Allen et al., 2000; Carmichael and Iyasu, 1998; Joseph et al., 1998) (Chapters 1 and 2 and Appendix B). The United States ranked 28th of 37 industrialized nations in infant mortality in 2001 and has a higher rate of low birth weight. Although increasing preterm birth rates and racial and ethnic disparities in the rates of preterm birth have been implicated, methodological factors are contributors to these differences (Chapter 2 and Appendix B). For example, efforts at resuscitating infants born at the lower limit of viability, thereby classifying them as live births (not still-births), increases the rate of infant mortality because so many infants born before 24 weeks of gestation die (Alexander et al., 2003; CDC, 2005i; MacDorman et al., 2005). The dearth of international comparisons of preterm birth rates is due to similar methodologic concerns about how gestational age, live births, and fetal deaths are recorded and reported (Appendix B).
The rate of infant mortality among African American populations in the United States in 2000 was 14.1 per 1,000 live births, more than twice the national average of 6.9 per 1,000 live births (NCHS, 2002). The rate of access to high-quality neonatal intensive care varies by race and ethnicity (Alexander et al., 2003; Morales et al., 2005; Wise, 2003). Preterm birth rates for African Americans are more than twice those for of Hispanic or white infants (Alexander et al., 2003). Although African American infants born preterm have had a survival advantage over white infants born preterm, this gap is narrowing, and the higher proportion of African American infants born preterm and the higher mortality rate among African American infants born full term play a greater