Preimplantation genetic diagnosis: the ethics of intermediate cases.

According to the current guiding principle regarding preimplantation genetic diagnosis (PGD), the technique should focus on the diagnosis of genetic defects which (may) affect the health of this particular potential child--the so-called 'medical model'. I argue in favour of a more permissive view, also allowing PGD of characteristics which may be relevant for the health of 'third parties'. Two cases are analysed: PGD/HLA typing in order to save a sib, and PGD/sex selection in order to prevent the birth of healthy female carriers of X-linked recessive disorders, who are at high risk of conceiving affected sons. While these cases are at odds with the medical model stricto sensu, they do have a link with health problems. In the first case, the health benefit hoped for is intrafamilial, in the second case the health benefit is transgenerational. These cases illustrate that the traditional dichotomy between the medical model on the one hand and the 'designer' or autonomy model on the other hand is simplistic--they represent an intermediate category.