Every person undergoing fertility treatment wants to make every effort to achieve the best possible outcome. Although IVF success rates have increased over the last 20 years, many practices still follow rigid protocols for most of their patients. Like many other areas of medicine, infertility is a highly complex condition and no two patients are similar. IVF doctors and scientists have been working tirelessly trying to improve their success rates. Interestingly, the focus of the scientific efforts has mostly been around the female oocyte and the male sperm, while studies on the importance of the endometrium have been considerably less in number (see figure)


Endometrial Receptivity Testing


What is the endometrium and why is it important? 

The endometrium is the tissue that lines the cavity of the uterus. It gradually becomes thicker as it prepares for the embryo to implant during your menstrual cycle. If the egg is not fertilized or if an embryo does not implant, then the endometrium begins to shed and the woman gets her period. The endometrium is a dynamic tissue layer. As it thickens during the menstrual cycle, it only allows implantation during a narrow time fragments, the so-called ‘window of implantation’.


How can the window of implantation affect your success rate?  

This window is not identical in timing and duration for all women. Consequently, for IVF to have high success rates, knowing the ideal time to transfer your embryo can be immensely helpful. Patients that have been troubled with two or more previous unsuccessful embryo transfers may demonstrate a different window of implantation. This is especially true if you’ve had a history of 2 or more unsuccessful embryo transfers. If the embryos you’re transferring are good quality but they have not implanted in the uterus, then careful consideration should be given to assessing the receptivity of the endometrium further.


What is the Endometrial Receptivity test?

Endometrial Receptivity Array (ERA) testing meticulously assesses the endometrial receptivity based on the expression of 248 different genes. This helps identify your individual, optimal window of implantation. Based on the available published data, up to 38% of women with previous implantation failure may have a displaced window of implantation. In other words, their previous failed attempts may have been due to the fact that their embryo transfer was mistimed.


How is the ERA test performed?

The test is performed by taking a very small sample from the endometrium using a tiny, flexible catheter. The sample is then cooled and sent for analysis. The day and time of the endometrial testing requires careful planning as it needs to be performed at a particular day for the result to be accurate. Consequently, you will be required to take the exact medication in the same way as you would for a frozen embryo transfer in preparation for the test.


Is there scientific data to back the use of the ERA test? Endometrial Receptivity Testing

There are numerous studies backing the use of this test, particularly for women with recurrent implantation failure or women with previous failed transfers of good quality embryos, including embryos that underwent genetic testing and were found to be normal. These studies have shown that in selected groups of patients the pregnancy rates may be as high as 75% in these otherwise difficult cases.


How can I interpret the results?

The results of the ERA test need to be interpreted by an experienced specialist, who will then carefully plan your embryo transfer accordingly. Dr. Christopoulos can help you arrange, perform and interpret the results of the ERA test so that you put yourself at the optimal position for a successful outcome. Please feel free to email us at info@arkivf.co.uk to arrange your complimentary, video consultation.


Scientific references

Díaz-Gimeno P, Horcajadas JA, Martínez-Conejero JA, Esteban FJ, Alamá P, Pellicer A, Simón C. A genomic diagnostic tool for human endometrial Receptivity based on the transcriptomic signature. Fertil Steril. 2011; 95(1):50-60, 60.e1-15.

Díaz-Gimeno P, Ruiz-Alonso M, Blesa D, Bosch N, Martínez-Conejero JA, Alamá P, Garrido N, Pellicer A, Simón C. The accuracy and reproducibility of the endometrial Receptivity array is superior to histology as a diagnostic method for endometrial Receptivity. Fertil Steril. 2013; 99(2):508-17.

Clemente-Ciscar M, Ruiz-Alonso M, Blesa D, Jimenez-Almazan J, Bahceci M, Banker M et al. Endometrial receptivity analysis (ERA) using a next generation sequencing (NGS) predictor improves reproductive outcome in recurrent implantation failure (RIF) patients when compared to ERA arrays. Hum Reprod. 2018; 33(Supp1):8-8.

Findikli N, Gultomruk M, Boynukalin K, Kavrut M, Oral E, Bahceci M. Combinatorial use of Endometrial Receptivity Array (ERA) and PGT-A can improve the clinical outcome in cases with previous ART failures. Hum Reprod. 2018; 33(Supp1):84-85.

Hashimoto T, Koizumi M, Doshida M, Toya M, Sagara E, Oka N. et al. Efficacy of the endometrial Receptivity Array for repeated implantation failure in Japan: A retrospective, two-centers study. Reprod Med Biol. 2017; 16(3):290-296.