RESUMEN
We examine how patients' medical expertise influences adherence to clinical guidelines for a treatment that is common, costly, and rationed by the clinical guidelines. Using administrative data on prenatal diagnostic testing (PDT), we compare the testing rates of medically trained patients (experts) and non-medically trained patients (non-experts) on the margin of eligibility thresholds in clinical guidelines. We find that experts are 9 percentage points more likely to receive PDT than non-experts when they are not eligible for testing and that more than 80% of the difference can be attributed to medical expertise. Our results suggest that the design of clinical guidelines is important for adherence and that having medical expertise as a patient affects treatment, when there is room for a deviation from the guideline.