Chapter II Racial/Ethnic Disparities in Birth Outcomes

Racial/ethnic differences in infant mortality are evident in trends over time and in the leading causes of infant death. Investigating these patterns can provide insight into these disparities. This chapter first presents racial/ethnic trends in rates of infant mortality. It then describes infant mortality rates during the neonatal and postneonatal period by race and ethnicity to offer a deeper understanding of how racial/ethnic disparities in birth outcomes show up at different times in an infant’s life. Infant mortality trends are examined from 1995 to 2002; 1995 is the earliest year with racial/ethnic infant mortality data publicly available through the National Center for Health Statistics, while 2002 is the latest year with data available by racial/ethnic groups, including White, Black, Asian/Pacific Islander, American Indian/Alaska Native, and Hispanic.

RACIAL/ETHNIC TRENDS IN INFANT MORTALITY

OVERALL TRENDS

Decreases in infant mortality rates were observed for most racial and ethnic groups from 1995 to 2002, but the magnitude of the change varied by group. Significant decreases were observed for White (7.9 percent), Black (5.5 percent), Asian/Pacific Islander (9.4 percent), and Hispanic (11.1 percent) populations (Table II.1). The infant mortality rate decreased among American Indian/Alaska Natives by 4.4 percent during this period, although the change was not statistically significant. The large decrease in infant mortality among the Hispanic population was driven by those of Cuban (30.2 percent) and Mexican (10.0 percent) descent. Although Hispanics as a group had a lower rate of infant mortality than the overall U.S. rate, women of Puerto Rican descent had an infant mortality rate higher than the national average for all years reported.

Despite significant declines in the rate of infant mortality for most racial/ethnic groups, the racial/ethnic disparity in rates did not change between 1995 and 2002 (Table II.1). For each year during this period, the rate of infant mortality for Blacks overall and Black non-Hispanics was 2.3 times that of Whites. In addition, for each year during this period, American Indian/Alaska Natives had an infant mortality rate ranging from 1.4 to 1.7 times that of Whites, while Puerto Ricans had a rate ranging from1.3 to 1.5 times that of Whites. The ratio between White non-Hispanic and Hispanic infant mortality rates was similar and remained stable for all years.¹

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NEONATAL AND POSTNEONATAL MORTALITY

Racial/ethnic trends for neonatal and postneonatal death rates are similar to overall rates of infant mortality—Blacks, American Indian/Alaska Natives, and Puerto Ricans continue to have the highest rates of all races and ethnicities (Table II.2). American Indian/Alaska Natives have one of the highest rates of postneonatal mortality while they have a neonatal mortality rate lower than the rates for all races/ethnicities combined. These results indicate that racial/ethnic disparities in infant mortality among American Indian/Alaska Natives are largely driven by infant deaths occurring after the first month of birth. The opposite is true for Puerto Ricans—they have a neonatal infant death rate 23 percent higher than the overall rate for all races and ethnicities and a postneonatal rate only 4 percent above the overall rate. For Blacks, the racial/ethnic disparities in infant mortality are equally attributable to neonatal and postneonatal mortality rates— both neonatal and postneonatal mortality rates for Blacks are nearly twice the rates for all races/ ethnicities combined.

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CAUSES OF INFANT DEATH

In 2002, the five principal causes of infant mortality accounted for 55 percent of all infant deaths (Mathews et al. 2004). The five leading causes, in descending order, are: (1) congenital malformations, (2) preterm birth/low birthweight, (3) sudden infant death syndrome, (4) maternal complications, and (5) cord complications. Congenital malformations, the leading cause of infant mortality, contributed to 20 percent of all deaths. The second largest cause, disorders relating to short gestation (less than 37 weeks) and low birthweight (less than 2500 grams), accounted for another 17 percent of mortality. Eight percent of deaths were attributable to sudden infant death syndrome (SIDS). Newborns affected by maternal complications of pregnancy and complications of placenta, cord, and membrane explained another six and four percent of infant deaths, respectively.

Cause of death varied by race/ethnicity. Congenital malformations were the leading cause of death for White, Hispanic, Asian/Pacific Islander, and American Indian/Alaska Native populations in 2002, but preterm birth/low birthweight was the leading cause among the Black population (Figure II.1). Unlike other races/ethnicities, American Indian/Alaska Natives had SIDS as the second leading cause of infant mortality.

The variability in cause of infant death across racial/ethnic groups may help identify the areas where interventions to reduce disparities and improve birth outcomes would be most effective. For example, although Black women had higher infant mortality rates than White women for all five leading causes of infant mortality, the largest difference in rates between the two groups was for preterm birth/low birthweight infants— infants born to Black women had an infant death rate due to preterm birth/low birthweight four times higher than those born to White women (Figure II.1). This infant mortality pattern is consistent with the prevalence of preterm birth/low birthweight among the two races; Black infants are almost two times more likely than White ones to be born preterm/low birthweight (Martin et al. 2002b) (Appendix Table A.6). Preterm birth/low birthweight accounted for 30 percent of the disparity in infant mortality rates between White and Black infants, while SIDS and maternal complications accounted for seven percent each (Mathews et al. 2004). In addition, although the rate of infant mortality decreased for Blacks between 1995 and 2002, the rate of low birthweight births among Blacks remained stable during this period (Table II.3), as did deaths attributable to low birthweight/preterm births (data not shown).

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This pattern suggests that focusing on the prevention of preterm birth/low birthweight among Black infants could have a large impact on reducing racial/ethnic disparities in infant mortality.

Similarly, American Indian/Alaska Natives had the highest proportion of infant deaths attributable to SIDS; the infant death rate among this group was 2.2 times that of Whites (Figure II.1). This implies that concentrating on the reduction of SIDS among American Indian/Alaska Natives could decrease the disparity in infant mortality between the two groups by 24 percent (Mathews et al. 2004). Likewise, if Puerto Rican infant deaths due to congenital malformations, preterm birth/low birthweight, and maternal complications were reduced to the levels of White infants, the difference in their infant mortality rates would be cut in half (data not shown). In Chapter III the risk factors underlying poor birth outcomes, and the racial/ethnic disparities in these risk factors, are discussed.

¹As shown in Table II.1 (page 10), the infant mortality rate increased slightly from 2001 to 2002. The increase was spread among most race and Hispanic origin groups. The increase is attributed, in large part, to an increase in the number of very low birthweight infants (less than 750 grams). Among the other possible explanations for the slight rise in infant mortality are: (1) increase reporting of early fetal deaths; (2) extent of mothers’ medical risk factors (including maternal anemia, diabetes, and chronic hypertension); and (3)changes in the medical management of pregnancy (such as cesarean deliveries) (MacDorman et al. 2005).