World leading PGD experts are issuing a rebuttal to an article on preimplantation genetic diagnosis (PGD) published recently in the New England Journal of Medicine which claims that PGD shows no benefit to pregnancy outcome in patients with advanced maternal age (AMA). Drs. Santiago Munné, Jacques Cohen and Mireia Sandalinas, of Reprogenetics, a provider of PGD services in the USA and Europe, are calling the NEJM study flawed, referring to the authors' poor embryo biopsy technique, the failure of the test in a large percentage of the embryos, and the exclusion of two key chromosomes from testing.

Dr. Santiago Munné states "The NEJM study clearly shows that in inexperienced hands embryos can be damaged during a cell biopsy procedure. However, it must be kept in mind that with proper technique and methods, the benefits of PGD may well outweigh its risks."

It is well known that more than 50% of human embryos conceived in vitro via in vitro fertilization (IVF) are chromosomally abnormal; this high abnormality incidence contributes to poor IVF pregnancy outcomes since such embryos often either fail to implant or lead to early miscarriages. PGD is a technique whereby a single cell is removed from a 3-day old embryo in order to assess its chromosomes and determine whether it is genetically normal. Only those embryos that have been diagnosed as normal are then transferred to the uterus, in an effort to reduce both implantation failure and early loss due to abnormalities.

Dr. Munné adds, "In the NEJM study, the test failed to produce a diagnosis in 20% of the embryos- a figure that needs attention since it is at least double the 5-10% figure reported by the more experienced groups. Furthermore, in the NEJM study, these undiagnosed embryos were actually transferred to patients, resulting in a low 6% implantation rate compared to a relatively higher 14.7% implantation in a control group of patients whose embryos did not have a biopsy. This difference in implantation rates points to the irreversible damage incurred by the biopsied embryos, most likely as a result of improper biopsy technique in the centers that performed this study. Another major weakness of the study is the failure to analyze chromosomes 15 and 22, which are both commonly affected by abnormalities in embryos."

The NJEM study underscores the importance of proper technique during embryo biopsy. To minimize the possibility of loss of embryos, such highly complex and multifaceted testing such as PGD on human embryos should be strictly performed by qualified centers with specific expertise in this area.

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