This study examined the reasons for persistent differences between black and white neonatal mortality rates despite the development of neonatal intensive care units (NICU). The services and technologies of the NICU have contributed to the decline in the neonatal mortality rate in the United States; therefore, it is possible that differential access to NICU services explains the racial differences in neonatal mortality rates. It is also possible that racial patterns in rates of low birth weight account for the mortality rate differences.

Data utilized for this study included the number of live births to the Finger Lakes Region of upstate New York in 1982 and 1984 and information on infants admitted to the only NICU serving this region.

During 1983 and 1984, 86.9% of births were whites and 11.5% were blacks, while 73.4% of the birth among babies with low birth weight were whites and 24.4% were blacks. Thus, the rate of low birth weight babies was 2.5 times higher for blacks than whites. NICU admissions included 70.6% who were white and 29.4% who were non-white (82% of which were black). Thus, black infants were admitted 2.6 times as frequently as white infants, a pattern that appears proportional to the racial pattern in the rate of low birth weight babies. After excluding infants who were transferred from other hospitals, the NICU admission rate was still 1.14 times the white NICU admission rate.

Once admitted to the NICU, white and black infants were equally likely to survive. There were no race differences in mortality by birth weight category.

Using multivariate analysis, the author found that the racial pattern in low birth weight did not completely explain the racial pattern in NICU admissions (log-linear regression analyses, after adjusting for birth weight, indicated that blacks were still significantly more likely to use NICU). In assessing reasons for the racial pattern in admission to the NICU, the authors note that there was an important 'interaction effect' between black race and low birth weight, which indicated that having low birth weight plays a smaller role in NICU admissions among blacks than would be predicted. That is, blacks have a higher proportion of infants admitted to the NICU with birth weights at least 2500 grams (4.4% of blacks versus 1.9% of whites) than would be predicted.

The causes of death among black and white babies with normal birth weights were also examined: 70% of blacks and 64.3% of whites died of congenital anomalies, and 30% of blacks and 14.3% of whites died of complications of severe asphyxia, persistent fetal circulation, or meconium aspiration. Additionally, among whites, 10.7% died of infectious causes and 3.6% died of other causes.

In their conclusion, the authors note that the neonatal mortality rate for blacks was 2.15 times that of for whites. However, blacks were more likely than whites to use the NICU, indicating that access to NICU did not explain the racial pattern in neonatal mortality. Additionally, although blacks were more likely to be admitted to the NICU and were more likely to have low birth weight children, low birth weight did not explain the NICU admission rate difference.

Other factors that might explain the racial pattern in NICU admission include "simple bias" (because black infants are perceived as being more vulnerable or due to other financial or social reasons); black mothers might be identified as being at higher risk due to younger age, history of drug abuse, or hypertension, which may result in earlier referral to a tertiary care center; and birth weight alone might not be an adequate indicator of severity of illness. Thus, this study "questions whether simply reducing low birth weight rates will result in equalization of black and white neonatal mortality rates." It is noteworthy that a number of the deaths in the normal birth weight categories were considered "potentially preventable." The authors argue that "programs aimed at reducing the black neonatal mortality rate must identify factors that result, not only in higher birth weight, but also in healthier babies as indicated by fewer perinatal and neonatal complications, fewer NICU admissions, and lower neonatal mortality rates."