Friday, July 06, 2007

Preimplantation genetic diagnosis makes it harder to get pregnant

For some time now, women who are undergoing in vitro fertilization (IVF) procedures have had the option of using preimplantation genetic diagnosis (PGD) to screen for disease. To perform PGD, a single cell is taken from a three-day-old embryo and tested for known genetic conditions. Only those embryos that pass inspection would be implanted.

Some women who seek PGD have a family history of genetic conditions (such as Huntington disease) that they wish to avoid passing on. Others may simply figure that--since IVF procedures generally produce more embryos than will be implanted--they might as well choose the healthiest ones they can. Either way, the idea behind PGD is that it increases the odds of a woman having a healthy baby.

Turns out, however, that it may decrease the odds of a woman having a baby at all. A study published in the New England Journal of Medicine today reports that PGD reduces older women's (defined in the study as women age 35 to 41) chances of becoming pregnant by about one third. It isn't known why this happens. It had been believed that removing one cell didn't harm the embryo, but it looks like that may not be the case.

So--it might be the end of the road for PGD as a routine screening process for IVF patients. . . but stay tuned. At the very least, women who are heading down this road need to be fully informed about the possible risks and benefits of PGD before they decide to proceed with testing. . . or maybe even before they decide to pursue IVF.

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