The Case for PGD
On April 23, 2007, Bruce Goldman authored a byline for The Los Angeles Times entitled, “Not-so Natural Selection,” in which he outlined to readers the results of a Belgian study published by Human Reproduction in 2004. This study indicated that, among other things, the advanced reproductive technology Preimplantation Genetic Diagnosis (PGD) – when utilized as a tool for aneuploidy screening in women of advanced maternal age – yielded fewer successful pregnancies when compared with a control group. Goldman uses this to build a foundational argument supporting the opinions of unidentified industry experts, citing deficient substantiation of claims that PGD positively contributes to the “take-home baby rate.”
While the results of the Belgian study are no doubt reliable and noteworthy to be sure, they beckon mention of the following point: that PGD’s proven benefits rest in aiding the detection of single gene defects like cystic fibrosis or Huntington’s disease. “When planning PGD for infertility, the number of cells to be biopsied must be considered carefully,” explains Dr. Santiago Munné, an award-winning and internationally recognized leader in reproductive medicine research, director of Preimplantation Genetic Diagnosis at Reprogenetics, LLC and the co-author of a noted study(*) on the subject.
This may account for the discrepancy between American and Belgian study results. Whereas European groups remove two cells for biopsy, American groups rely on the use of just one cell. Removal of up to one-third to one-half of embryonic tissue versus a single cell may be the defining difference in the embryo’s ability to continue to develop and divide appropriately.
As with any technology, patients must be advised of risks and benefits associated with the procedure. For women of advanced maternal age, as was cited in The Los Angeles Times – and who mainly comprise a high-risk group of patients for whom there is increased risk for chromosomal abnormality – PGD serves another function not addressed in the article. When observing embryos for high-risk groups, such as women of advanced maternal age, women with recurrent pregnancy loss, women with two or more failed in-vitro fertilization (IVF) cycles and couples where the male has severe male factor; 25 to 30 percent of these patient have all embryos abnormal. Thus, PGD allows patients within these high-risk groups an assessment on their likelihood of conceiving and consideration of alternative options.
In instances where aneuploidy is consistent, PGD can help women turn a corner from their painful position of, “If I just keep trying IVF, I will eventually get pregnant.” The technique provides answers that allow these women to search for other options such as traditional adoption, use of donor eggs or donor embryos. Of course, every patient’s case needs to be evaluated on an individual basis and no process is 100 percent accurate; however, PGD can be beneficial for a number of reasons – including its ability to answer patient queries as to why they haven’t conceived in the past or why repetitive results may indicate a need to look at other options.
Clearly, there need to be guidelines for how PGD is used. But through application of the technique, multifetal gestational rates can effectively be reduced – a point not mentioned by Goldman (LA Times, 2007). By transferring fewer healthier embryos, the likelihood of a pregnancy resulting in twins and triplets is dramatically reduced.
Perhaps Goldman’s closing thoughts on the impact that an embryo experiences from removal of its genetic material deserve greater attention. Attributing results of a Belgian study to the PGD pregnancy rates of American patients, becomes an apples-to-oranges comparison – one that acts as a disservice to the thousands of couples nationwide who aspire to build a family through advanced reproductive technologies.
(*) Cohen, J., Munné, S. & Wells, D. (2007). Removal of 2 cells from cleavage stage embryos is likely to reduce the efficacy of chromosomal tests that are used to enhance implantation rates. Fertility and Sterility (Vol. 87, No. 3), p.495-502.
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http://www.latimes.com/features/health/medicine/la-he-pgd23apr23,1,5376531.story?coll=la-health-medicine
Article excerpt below:
Not-so natural selection
A procedure called PGD is used to prevent inherited disorders, but can it improve in vitro pregnancy rates?
By Bruce Goldman
Special to The Times
April 23, 2007
BIOPSIES are a pain. When they're medically necessary we put up with them. When they're not, most of us would just as soon remain un-punctured.
When the patient is a 3-day-old embryo, it's especially fair to ask for some evidence of a clear medical benefit.
Pre-implantation genetic diagnosis, or PGD, is a procedure sometimes performed in conjunction with in vitro fertilization to improve the quality of the embryos selected. It entails the careful isolation of one of a 3-day-old embryo's eight or so cells, then analysis of that cell's genetic contents. Based on what is found, IVF patients and doctors can decide which embryos to transfer into the woman's uterus.
Use of PGD has risen exponentially since its inception 17 years ago. In the U.S., where PGD isn't formally tracked, about 3,000 procedures were performed in 2005, according to a recent report from the Genetics & Public Policy Center, which is affiliated with Johns Hopkins University. Experts estimate its frequency is rising annually by 15% to 30%.
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