Screening embryos for genetic abnormalities before implantation does not improve the chances of IVF success, according to research at a top New York fertility clinic.
There is no evidence that recent technical improvements in preimplantation genetic screening (PGS) improve IVF pregnancy chances, according to a paper just published online in the Journal of Assisted Reproduction and Genetics1. The review, by two fertility specialists from New York's Center for Human Reproduction (CHR), raises important questions, as this "new" PGS is actively marketed to patients as "proven" and "established" to increase IVF success rates.
In the late '90s, PGS was widely utilized in IVF in attempts to improve pregnancy chances. The assumption was it could eliminate genetically abnormal embryos before implantation, thereby raising implantation and pregnancy rates, and reducing miscarriage rates. For a number of years, thousands of women worldwide underwent PGS under this premise, until a number of investigators, including the authors of this new report, demonstrated that, in practice, PGS actually reduced IVF pregnancy rates, at least in older women. By 2008, the American Society of Reproductive Medicine (ASRM) and other authoritative bodies declared PGS ineffective in improving IVF outcomes.
In recent years, a number of important technical improvements were introduced to PGS, which, unquestionably, improved the accuracy of determining chromosomal abnormalities in embryos prior to transfer. Under the assumption that these improvements would finally confirm the widely held opinion that PGS will improve IVF pregnancy rates, a "new" form of PGS is now, once again, aggressively marketed by commercial interests.
After a thorough review of published studies and ongoing registered clinical trials, the paper concludes that there is no evidence that this reintroduction of PGS to IVF improves pregnancy rates. "As we already pointed out in 2008, evidence suggests that the real reason why PGS was ineffective in its first introduction and, likely, remains ineffective in its current reincarnation, is the wrong patient selection, and not the techniques utilized," explains Norbert Gleicher, MD, Medical Director and Chief Scientist of CHR. "Until we better identify appropriate patient populations for PGS, new techniques are unlikely to benefit patients and, as previously, may actually reduce IVF pregnancy chances."
"These new techniques, indeed, further complicate considerations about patient selection," adds David H Barad, MD, Director of Clinical ART and Senior Scientist at CHR. "With the "new" PGS, embryos have to remain in culture for 5-6 days after fertilization, which many embryos of lesser quality do not survive. Some of these embryos would still lead to pregnancy if transferred on day-3, as in routine IVF cycles." He continues: "Reported higher pregnancy rates with the 'new' PGS are misleading because they exclude patients who started IVF cycles but never made it to embryo transfer."
The paper concludes that the "new" PGS still has to be considered "experimental" and patients should be advised accordingly. "Patients should be aware that PGS is not in any way proven to better pregnancy chances, and may actually do the opposite in some patients," warns Dr. Gleicher.
1Gleicher N and Barad DH. A review of, and commentary on, the ongoing second clinical introduction of preimplantation genetic screening (PGS) to routine IVF practice. J Assist Reprod Genet 2012; epub ahead of print. (http://link.springer.com/article/10.1007/s10815-012-9871-2/fulltext.html)
About Center for Human Reproduction
The Center for Human Reproduction (CHR, http://www.centerforhumanreprod.com/), located in New York City, is a leading clinical fertility and research centers in the world, having contributed many important innovations to the treatment of infertility. As "fertility center of last resort," CHR routinely treats women from all over the world, with during 2011 over half coming from outside the New York tri-state area, approximately a quarter from overseas. Dr. Gleicher and Dr. Barad are available for further comments.