Objective: To determine how pregnant women of varying ages, races, ethnicities, and socioeconomic backgrounds value procedure-related miscarriage and Down–syndrome-affected birth. Methods: We studied cross-sectionally 534 sociodemographically diverse pregnant women who sought care at obstetric clinics and practices throughout the San Francisco Bay area. Preferences for procedure-related miscarriage and the birth of an infant affected by Down syndrome were assessed using the time trade-off and standard gamble metrics. Because current guidelines assume that procedure-related miscarriage and Down syndrome–affected birth are valued equally, we calculated the difference in preference scores for those two outcomes. We also collected detailed information on demographics, attitudes, and beliefs. Results: On average, procedure-related miscarriage was preferable to Down syndrome–affected birth, as evidenced by positive differences in preference scores for them (time trade-off difference: mean = 0.09, median = 0.06; standard gamble difference: mean = 0.11, median = 0.02; P < .001 for both, one-sample sign test). There was substantial subject-to-subject variation in preferences that correlated strongly with attitudes about miscarriage, Down syndrome, and diagnostic testing. Conclusion: Pregnant women tend to find the prospect of a Down syndrome–affected birth more burdensome than a procedure-related miscarriage, calling into question the equal risk threshold for prenatal diagnosis. Individual preferences for those outcomes varied profoundly. Current guidelines do not appropriately consider individual preferences in lower-risk women, and the process for developing prenatal testing guidelines should be reconsidered to better reflect individual values.