OBJECTIVE We tested whether adding interpretive labels (eg, "negative test") to prenatal genetic screening test results changes perceived risk and preferences for amniocentesis. METHODS Women (N = 1688) completed a hypothetical pregnancy scenario on the Internet. We randomly assigned participants into 2 groups: high risk of fetal chromosomal problems (12.5/1000) or low risk (2/1000). After prenatal screening, estimated risk was identical (5/1000) for all participants, but results were provided either alone or with interpretive labels. RESULTS When receiving test results without labels, all participants react similarly. With labels, the participants who received "positive" or "abnormal" results reported a higher perceived risk (P < .001), greater worry (P < .001), and greater interest in amniocentesis (57% vs 37%; P < .001) than did the participants who received "negative" or "normal" results. CONCLUSIONS Interpretive labels for test results can induce larger changes to a woman's risk perception and behavioral intention than can numeric results alone, which create decision momentum. This finding has broad clinical implications for patient-provider communication.