Fertility Specialists Urge Re-evaluation of Current Concepts of Embryo Selection in IVF

NEW YORK, Feb. 16, 2015 /PRNewswire/ -- Investigators from The Center for Human Reproduction (CHR), a leading fertility research and treatment center in New York City, argue for reconsideration of currently popular methods of embryo selection in association with in vitro fertilization (IVF) in a recently published paper. In a large majority of patients, embryo selection methods do not improve IVF outcomes and in some patients may reduce pregnancy and live birth chances.

Based on the observation that longer embryo culture selects embryos with highest implantation chances, blastocyst-stage embryo transfer (BSET) of embryos, which involves culture of embryos for 5 days after fertilization, is gaining popularity in IVF. In a recent article published in the online journal Reproductive Biology and Endocrinology, investigators from CHR, however, point out that BSET also has significant downsides, the largest being that cumulative pregnancy chances (the chance of pregnancy from all eggs/embryos obtained from a single egg retrieval) are uniformly higher if embryos are transferred on day-3 rather than d-5 after fertilization. Because some embryos, if transferred on day-3, will lead to normal pregnancies and deliveries but will not survive in the laboratory to day-5, culturing embryos to day-5 uniformly reduces the cumulative pregnancy chances from a single egg/embryo cohort.

Good prognosis patients who produce large numbers of high quality embryos will, indeed, slightly improve their immediate pregnancy chances since day-5 culture will select out embryos with the highest pregnancy chances. But this applies to on average only about 20% of IVF patients. The remaining 80% will see either no outcome benefits or reduce their chances of pregnancy if they produce relatively small egg/embryo numbers, and the loss of individual embryos is statistically more relevant.

BSET forms the basis for two additional methods of embryo selection, which have been gaining in popularity: preimplantation genetic screening (PGS) and closed embryo incubation systems with time-lapse photography. The shortcomings of BSET automatically apply to both techniques. PGS tests the embryos' chromosomal makeup on the 5th day, and only chromosomally normal embryos are transferred to the patient's uterus, while time-lapse photography claims to be able to further select among embryos that survive culture to day-5.

"Published data clearly shows that blastocyst culture does not benefit most patients, and even reduces pregnancy chances in women with low functional ovarian reserve," David H Barad, MD, MS, Director of Clinical ART, Senior Scientist at CHR and a co-author of the article explains. "Women with low functional ovarian reserve do not have many embryos to choose from, and prolonged culture outside of the body only worsens their pregnancy chances."

Norbert Gleicher, MD, Medical Director and Chief Scientist of CHR adds, "Good-prognosis patients, to a minor degree, benefit from embryo selection via BSET; these patients, however, even without BSET, PGS and/or time-lapse photography demonstrate very good pregnancy chances, and it is unclear whether the small incremental benefit they achieve warrants the significant additional expense. But why the remaining 80% of patients, who will not gain outcome benefits, are asked to carry the very significant additional costs is unclear to us."

The full article is available at http://www.rbej.com/content/13/1/3.

About Center for Human ReproductionThe Center for Human Reproduction (CHR), located in New York City, is one of the world's leading clinical and research centers in reproductive medicine and infertility. CHR has special expertise in treatment of women with low functional ovarian reserve, and pioneered many innovations, which have become mainstays of infertility treatments worldwide. Drs. Barad and Gleicher are available for further comments. Contact: 212-994-4400 x.4491

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