Differences in gestational age-specific birthweight among Chinese, Japanese and white Americans.

This study investigated racial differences in gestational age-specific birthweight in a sample of 21,288 Chinese, 11,882 Japanese and 65,818 White resident singleton livebirths, obtained from the National Center for Health Statistics 1983 and 1984 linked birth/infant death cohort files. The gestational age-specific birthweight distributions of Chinese and Japanese were similar, but differed from those of Whites both in the mean level and in the variance. The mean birth-weights of Chinese and Japanese as compared to that of White infants were 4-5% lower among preterm births, and 5-6% lower among term births, after adjustment was made for gestational age, demographic variables, use of antenatal care and infant gender. The racial differences in gestational age-specific birthweight were even greater at the 90th percentile but smaller at the 10th percentile. These racial differences should be considered in both clinical evaluation of newborns and in epidemiological studies. Significant interactions were found between race and such maternal variables as education, marital status, birthplace, and month during which antenatal care began. It suggests that recognition of racial differences in risk factors and exposure-response relationships may be valuable in specifying interventions for intrauterine growth retardation among different racial groups.