Clinical determinants of the racial disparity in very low birth weight

Although the risk of very low birth weight (less than 1500 g) is more than twice as high among blacks as among whites in the United States, the clinical conditions associated with this disparity remain poorly explored.

We reviewed the medical records of over 98 percent of all infants weighing 500 to 1499 g who were born in Boston during the period 1980 through 1985 (687 infants), in St. Louis in 1985 and 1986 (397 infants), and in two health districts in Mississippi in 1984 and 1985 (215 infants). The medical records of the infants' mothers were also reviewed. These data were linked to birth-certificate files. During the study periods, there were 49,196 live births in Boston, 16,232 in St. Louis, and 16,332 in the Mississippi districts. The relative risk of very low birth weight among black infants as compared with white infants ranged from 2.3 to 3.2 in the three areas. The higher proportion of black infants with very low birth weights was related to an elevated risk in their mothers of major conditions associated with very low birth weight, primarily chorioamnionitis or premature rupture of the amniotic membrane (associated with 38.0 percent of the excess proportion of black infants with very low birth weights [95 percent confidence interval, 31.3 to 45.4 percent]); idiopathic preterm labor (20.9 percent of the excess [95 percent confidence interval, 16.0 to 26.4 percent]); hypertensive disorders (12.3 percent [95 percent confidence interval, 8.6 to 16.6]); and hemorrhage (9.8 percent [95 percent confidence interval, 5.5 to 13.5]).

The higher proportion of black infants with very low birth weights is associated with a greater frequency of all major maternal conditions precipitating delivery among black women. Reductions in the disparity in birth weight between blacks and whites are not likely to result from any single clinical intervention but, rather, from comprehensive preventive strategies.