Down syndrome screening using race-specific femur length

Objective The study was undertaken to evaluate the influence of maternal race on fetal femur length when screening for Down syndrome. Study design We reviewed our patient databases to obtain fetal biometry from 15 to 22 weeksʹ gestation, maternal race, and cases of Down syndrome. Institution and race-specific regression lines for femur length (FL) to biparietal diameter (BPD) were created. The efficiency of using published expected FL was compared with our institution and race-specific regression in screening for Down syndrome. Results There were 4350 African American, 4271 white, 2315 Hispanic, and 654 Asian subjects and 42 cases of Down syndrome (1:276) included in the study. Our institutionally derived regression for FL by BPD had an R2 of 0.82. Regression lines for FL by BPD generated by race had an R2 of 0.86, 0.84, 0.83, and 0.80 for African American, Hispanic, Asian, and white subjects, respectively. The race-specific regression was no better than institution-specific data. Conclusion Using institution-specific FL was more efficient in screening for Down syndrome than published expected FL; race-specific analysis did not improve efficiency.