Humerus length evaluation in different ethnic groups.

OBJECTIVE: Femoral length has gained much attention for its use as a marker for Down syndrome, and racial variation has been evaluated. We hypothesized that no racial differences in humerus length will be shown from 14 to 22 weeks' gestation. METHODS: Our sonography database was queried from January 1, 1994, to September 30, 2001, for obstetric sonographic examinations of singleton fetuses. Cases with incomplete data, fetal anomalies, and cases without documented ethnicity were excluded. Only 1 examination per fetus was used. Individual parameters were evaluated from 14 to 22 weeks' gestation in white non-Hispanic, Hispanic, African American, Asian, and Eastern Indian women. Linear regression was used to model the relation of humerus length to menstrual age and to compare the humerus length for gestational age among ethnic groups. We compared the sensitivity for Down syndrome detection from a standard expected humerus length formula and ethnic-specific formulas. RESULTS: We identified 1164 fetuses: 380 white, 224 Hispanic, 432 African American, 116 Asian, and 12 Eastern Indian. Comparing with white fetuses, we found differences in humerus length among African American (P < .001) and Asian (P < .001) fetuses but not among Hispanic fetuses (P = .98). The sensitivity for Down syndrome detection from standard and ethnic-specific formulas was identical. CONCLUSIONS: In this cohort, small differences in humerus length exist among ethnic groups. These differences did not affect the sensitivity of expected humerus length as a marker of Down syndrome in our diverse population.