Preimplantation genetic diagnosis principles and ethics.

Preimplantation genetic diagnosis (PGD) followed by implantation of unaffected embryos offers high-risk couples the option to decrease the risk of genetic disease in their offspring without the dilemma of a prenatal diagnosis that may be followed by a termination of pregnancy. Polar body, blastomere and blastocyst biopsies are currently being performed, whereas the two major technologies used for single-cell genetic analysis involve the polymerase chain reaction and fluorescence in-situ hybridization. PGD, similar to other prenatal diagnosis methods, raises many ethical and legal dilemmas. The high cost of practice and the low pregnancy rate achieved are still considered the major drawbacks of this new procedure.