Preimplantation diagnosis of genetic disease

If a couple is known to be at risk of transmitting a severe genetic disease to their offspring, the fetus may be tested by chorionic villus sampling or amniocentesis during pregnancy. If the fetus proves to be affected, the couple has the option of terminating the pregnancy. Recently, an alternative approach has been developed, i.e. to screen embryos produced by in vitro fertilization before implantation. Diagnostic analysis is carried out on a single cell removed by micromanipulation from the 8-cell embryo or on the polar body from the unfertilized egg. Preimplantation diagnosis is now a feasible alternative to screening during pregnancy and may be the preferred route for some couples.