DIFFERING BIRTH-WEIGHT AMONG INFANTS OF US-BORN BLACKS, AFRICAN-BORN BLACKS, AND US-BORN WHITES

Background In the United States, the birth weights of infants of black women are lower than those of infants of white women. The extent to w hich the lower birth weights among blacks are related to social or gen etic factors is unclear.Methods We used vital records for 1980 through 1995 from Illinois to determine the distribution of birth weights amo ng infants born to three groups of women - U.S.-born blacks, African-b orn blacks, and U.S.-born whites. Results The mean birth weight of 44, 046 infants of U.S.-born white women was 3446 g, that of 3135 infants of African-born black women was 3333 g, and that of 43,322 infants of U.S.-born black women was 3089 g. The incidence of low birth weight (w eight less than 2500 g) was 13.2 percent among infants of U.S.-born bl ack women and 7.1 percent among infants of African-born black women, a s compared with 4.3 percent among infants of U.S, born white women (re lative risks, 3.1 and 1.6, respectively). Among the women at lowest ri sk (those 20 to 39 years old, with 12 years of education for themselve s and their spouses, early prenatal care, gravida 2 or 3, and no previ ous fetal loss), the rate of low birth weight in infants of African-bo rn black women (3.6 percent) was closer to the rate in infants of U.S, born white women (2.4 percent), and the rate in infants of U.S.-born black women remained high (7.5 percent). Conclusions The birth-weight patterns of infants of African-born black women and U.S.-born white wo men are more closely related to one another than to the birth weights of infants of U.S.-born black women. (C) 1997, Massachusetts Medical S ociety.