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Endometrial Receptivity Array Can Determine Embryo Implantation

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May 2, 2013

Recent theories in the field of reproductive medicine are moving away from citing the embryo as the sole determinant of an in vitro fertilization (IVF) cycle’s success. While it is true that embryo quality is the strongest predictor of implantation, current research shows that uterine receptivity may also play a fairly significant role in the success of a cycle. In fact, some of the latest reproductive findings encourage patients to freeze their embryos and transfer them in a later cycle once the uterine lining has recovered from the effects of harsh fertility drugs.

A new test, the Endometrial Receptivity Array (ERA), operates on a similar premise and provides insight into how receptive a woman’s uterus will be at a particular stage in her menstrual cycle. Essentially, this will help fertility doctors to determine the best time to transfer an embryo in hopes that it will implant.

Barry Behr, Ph.D., H.C.L.D., Embryologist and Director of the IVF Lab at Stanford Fertility and Reproductive Medicine Center, and Co-Founder of Ivigen, says endometrial biopsy in a cycle before embryo transfer can predict which day implantation may occur in a subsequent cycle. “The [ERA] test is still being evaluated in an international controlled trial and could be argued as a personalized window of implantation,” he says. The purpose of the clinical trial is to determine whether or not this test is something to be recommended for every fertility patient or only for those who have suffered failed IVF cycles. “We are not hand waving or saying everyone should do [the ERA test]. Several studies by the inventor showed improvement of implantation, but it has to meet the scientific rigor of a controlled trial. We feel there is enough evidence to make it available while it is still in the clinical trial phase. The results will either say this is a test everyone should do before IVF or the last thing to try if IVF has failed previously,” Behr explains.

Typically, embryo transfers are performed between day three and day five after retrieval. The time of transfer is determined as a direct result of embryo development. Embryos that stand a strong chance of growing in the lab until day five are transferred as blastocysts. Those that show less progressive growth can be transferred earlier in hopes of achieving implantation.

The quality of embryos is the best predictor of success, but for couples who do not conceive even after genetic testing like preimplantation genetic diagnosis (PGD) or preimplantation genetic screening (PGS), there could be endometrial factors involved. The ERA test is the first of its kind to examine endometrial receptivity as a product of gene expression of the endometrial lining at specific times during a woman’s cycle. The test looks at the cyclical pattern of 238 different genes.

The ERA test is mailed to the fertility clinic in the form of a kit and involves an endometrial biopsy, similar to a pap smear. The biopsied tissue is then sent back to the lab where results are processed and delivered within one to two weeks. Embryologists and fertility doctors can then make a collaborative decision as to when an embryo should be thawed and transferred in a natural cycle. “This is not something we would do in a transfer cycle because we want it to be atraumatic and to be able to time the biopsy results with transfer,” Behr apprises.

The cost of the test is $450, a relatively inexpensive price when considering the overall costs of fertility treatment and potential benefits of understanding endometrial receptivity.


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