The screening called pre-implantation genetic screening (PGS) for aneuploidy involves the testing of a single cell from a three-day old embryo. It is similar to PGD, a test that looks for specific genes known to cause inherited diseases. Preimplantation-screening of IVF embryos is expensive-the technique virtually doubles the procedure’s overall cost. Until now, eggs from younger women were generally considered to be more frequently defect-free. This concept has been challenged.
Dr. Jeffrey Nelson of the HuntingdonReproductiveCenter in California used PGD to screen 289 embryos from 22 healthy egg donors under the age of 30. “Overall, 42% of the embryos had aneuploidy or abnormal chromosomes.” Two other studies, one in Maryland and one in Atlanta, conducted similar studies and also detected unexpectedly high incidences of embryos with chromosomal abnormalities in women once considered at reduced risk for such. Doctors are unclear as to whether the drugs used for IVF are responsible for such inflated risk or if defective eggs are common among the genetic population but are rejected early on by the body.
While most agree that the results have challenged traditional thinking, the ensuing recommendations vary from the radical to the cautious. Dr. Nelson believes the UK Human Fertilisation and Embryology Authority should relax its guidelines and recommend wider IVF screenings. A spokesman from the HFEA answers, “we are concerned that women are properly aware of the potential risks before they choose to have this test and that women and embryos are not tested unnecessarily. Mr. Stuart Lavery, a consultant gynecologist atHammersmithHospitaland a spokesman for the British Fertility Society, said “it’s very interesting, but it is quite preliminary.” He recommended that caution still be exercised when considering wider screening, as the procedure is relatively new and can be invasive. “He said the benefits would have to outweigh any harms.”