ABSTRACT
For couples at risk of transmitting a genetic disease, pre- implantation genetic diagnosis (PGD) and transfer of dis- ease-free embryos offer alternatives to prenatal diagnosis by chorionic villous sampling or amniocentesis, followed by therapeutic abortion of affected fetuses. Molecular PGD was initially employed for embryo sexing in couples at risk for X-linked diseases. The technique used polymerase chain reaction (PCR) to amplify Y chromosome-specific sequences, and only embryos diagnosed as females were transferred (1). During the last two decades, the range of genetic abnormalities that can be detected by PGD has increased exponentially and in fact it may be performed for virtually any genetic disorder for which the mutation has been detected. PGD can also be employed in carriers of cancer predisposition genes and other late-onset genetic conditions. This, however, raises many ethical and practi- cal questions. For instance, familial adenomatous polypo- sis (FAP) is an autosomal dominant syndrome with almost 100% risk of colorectal cancer without prophylactic col- ectomy. In a study including 20 individuals with FAP, 95% would consider undergoing prenatal testing and 90% would consider PGD (2). In comparison, carriers of BRCA1 or BRCA2 mutations are at risk for breast and/or ovarian cancer, but at a comparatively lower risk of developing malignancy. A similar survey conducted among such car- riers revealed that 75% felt it was acceptable to offer PGD for this indication, but only 14% of patients contemplating a future pregnancy would consider PGD themselves (3).
