OBJECTIVES: We assessed socioeconomic differences in probabilities of prenatal diagnoses of Down syndrome and continuation of pregnancies after such diagnoses, along with the effects of these differences on disparities in live-birth prevalences of Down syndrome. METHODS: Using population-based data derived from 1433 cases of Down syndrome and 3731 control births, we assessed age-adjusted effects of maternal occupation and geographic origin on prenatal diagnoses, as well as overall and live-birth odds, of Down syndrome. RESULTS: Maternal occupation and geographic origin had significant effects on the probability of a prenatal diagnosis of Down syndrome and on continuation of pregnancy after such a diagnosis. Women in lower-status occupational categories had higher odds of delivering a live-born infant with Down syndrome. In comparison with women in the highest-status occupational category, the age-adjusted odds ratio for a Down syndrome live birth among women without an occupation was 2.4 (95% confidence interval [CI] = 1.7, 3.3). By contrast, there were no disparities in age-adjusted overall likelihood of Down syndrome. CONCLUSIONS: Socioeconomic differences in use of prenatal testing have created disparities in the live-birth prevalence of Down syndrome. Overall Down syndrome risk does not vary according to socioeconomic status.