Prevention is crucial in clinical medicine, public health and epidemiology (Prevention – Picture of America, 2023; Clarke, 1974; Natl, Res, Counc., 1978). Preventive measures are traditionally classified in three types: primary, secondary, and tertiary prevention (Prevention – Picture of America, 2023; White, 2020). This distinction allows to map each type of prevention to different moments of the natural history of disease model, which could be considered a causal model (White, 2020). Particularly in clinical medicine, preventive interventions are commonly studied as strategies of primary or secondary prevention. For example, a randomized-controlled trial (RCT) could be designed in which aspirin was given to healthy adults to prevent the occurrence of a first myocardial infarction (primary prevention). Alternatively, an RCT could be performed in which aspirin was given to people who have had a stroke to prevent another stroke (secondary prevention). However, designing studies should not be based purely on whether the intervention is aimed at primary or secondary prevention, but rather using the disease's causal model as a basis. For instance, if we evaluated aspirin as secondary prevention of stroke in a hypothetical RCT, we would be including only people who have had a stroke in the past. This would mean excluding people that have not had a stroke but could be at high risk of it due to another risk factor and thus, could potentially benefit from aspirin. As an illustrating example, let us examine the case of aspirin for prevention of preeclampsia (a severe hypertensive disorder of pregnancy).