Frequency of prenatal cytogenetic diagnosis and pregnancy outcomes by maternal race-ethnicity, and the effect on the prevalence of trisomy 21, Metropolitan Atlanta, 1996-2005.

The prevalence of trisomy 21 has been reported to differ by race-ethnicity, however, the results are inconsistent and the cause of the differences is unknown. Using data from 1996 to 2005 from the Metropolitan Atlanta Congenital Defects Program (MACDP), we analyzed the use of prenatal cytogenetic testing and the subsequent use of elective termination among pregnancies affected with any MACDP-eligible birth defect and trisomy 21, by maternal race-ethnicity. We then examined whether these factors could explain the observed differences in the prevalence of trisomy 21 among race-ethnicity groups. Among all pregnancies with birth defects, prenatal cytogenetic testing as well as elective terminations after an abnormal prenatal cytogenetic test result were observed less frequently among Hispanic women than among non-Hispanic white women (odds ratio [OR] 0.66, 95% confidence interval [CI] 0.56-0.78, respectively). In pregnancies affected by trisomy 21, both the Hispanic and the non-Hispanic black populations had more live births (89.5% and 77.8%, respectively) and fewer elective terminations (5.7% and 15.2%, respectively) compared to the non-Hispanic white population (63.0% live births, 32.3% elective terminations). After adjusting for elective terminations, non-Hispanic white mothers had a higher live birth prevalence of trisomy 21 compared to non-Hispanic black (OR 0.64, 95% CI 0.54-0.76) or Hispanic mothers (OR 0.69, 95% CI 0.55-0.86). Overall, our data suggest that factors associated with decisions made about the use of prenatal testing, and about pregnancy management after testing, might play a large role in the race-ethnicity differences observed in the live birth prevalence of trisomy 21.