Endometrial Receptivity Array (ERA) is the diagnostic procedure that may help to determine whether the endometrial cavity is ready for embryo implantation. Endometrium refers to the inner lining of the uterus to which the embryo must attach itself after fertilization. The endometrium plays a key role in the implantation of an embryo during IVF. The ERA test is meant for evaluation of the functioning of the genes that determine the receptivity of the endometrium. There are over 238 genes that must be assessed through the ERA test. It can also help predict the ideal window of implantation for a particular woman. By doing this, IVF specialists can time the implantation to reduce the chance of the implantation failure.

IVF is one of the most famous fertility treatments available. Though it does not guarantee conception, most patients are expected to conceive within 3 IVF cycles. However, some women fail to conceive even after 3 cycles of IVF. In such cases, doctors then begin to search for the reasons why the woman has been unable to conceive. Receptivity of the uterus is one of the possible reasons for this. This can be verified with an Endometrial Receptivity Array (ERA) test.

ERA (Endometrial Receptivity Analysis) assesses the optimum time in the endometrial cycle to perform embryo transfer. Thus, ERA can increase the chances of the pregnancy by synchronizing an implantation-ready embryo with a receptive endometrium.


The ERA is indicated for recurrent implantation failure (RIF) patients since such patients have a higher risk of having a displaced window of implantation. Therefore, this analysis could be beneficial for patients with the previous 2 failed cycles with their own eggs or the previous 1  failed cycle with egg donation, in both cases with good quality embryos transferred into the uterine cavity.

In case that your patient requires any intervention for other uterine factors, the ERA test must be done after such intervention, in order to reproduce as much as possible the conditions in which the embryo transfer will take place.

In case of atrophic (< 6 mm) or hypertrophic endometrium (> 12 mm), the ERA can be done if this condition is constant in all endometrial cycles for this patient.


Endometrial Receptivity Array uses Next Generation Sequencing (NGS) technology to analyze the gene expression of 248 genes related to the endometrial receptivity status. The results obtained from this test are based on the expression analysis of these genes with a computational predictor designed and developed by Igenomix. After sequencing the genetic material (RNA)obtained from an endometrial biopsy, it is possible to evaluate if the endometrium is Receptive or Non-receptive in a given moment of the endometrial cycle. This result can be used to give recommendations for the personalized embryo transfer in each patient according to patients’ specific endometrial profile. In a small number of cases (10%), it is necessary to establish the personalized window of implantation by performing a second endometrial biopsy on the specific day designated by the first ERA test.

To ensure that the ERA test is reproducible,  the test must be performed duplicating exactly the same conditions that the patient will undergo in the subsequent embryo transfer cycle (cycle type, treatment, way of administration…), and always in hormone replacement therapy cycles (HRT) or the natural cycles. This test can’t be performed in controlled ovarian stimulation cycles.

The first endometrial biopsy is done after 5 full days of progesterone administration (P+5) in an HRT cycle or 7 days after the hCG triggering (hCG+7) in a natural cycle.


An endometrial biopsy will be performed by your IVF specialist in a mock embryo transfer cycle prior to your IVF or FET cycle. This sample will then be analyzed to evaluate endometrial receptivity and the optimal day of embryo transfer. The sample will be sent to a lab where molecular analysis is done to determine the best time to attempt embryo implantation in a future transfer cycle. There are three potential results.

  • Pre-receptive: This indicates that the endometrium is not yet ready to receive the embryo and transfer at this time may not be ideal.
  • Receptive: This indicates that the moment the endometrial biopsy was taken as an optimal time for embryo transfer.
  • Post-receptive: This indicates that the endometrium had reached the stage of optimal embryo implantation but has now gone past it.


One of the most common questions that patients have regarding the Endometrial Receptivity Analysis and taking the endometrial biopsy is if it’s painful. The endometrial biopsy is an outpatient procedure, which does not require admission to a hospital. Some patients have described having either mild discomfort during the procedure or the mild cramping after. You can get over-the-counter pain medication to the address any discomfort, but you should first consult with your doctor.


IF you’ve just started trying to conceive, do not have a history of miscarriages, and/or have not previously undergone IVF, it may be early in the process to consider endometrial receptivity. As a patient when you have an initial fertility evaluation, your IVF specialist will first look at your ovarian reserve and ovarian function. They will also typically perform an ultrasound to look at your ovaries, uterus, and get an image of your uterine lining. Assessing your endometrial receptivity is not performed initially unless the doctor feels it’s warranted. If you have concerns or want to discuss this alternative, you should feel comfortable asking your physician about the ERA test.

Indicated for all the patients starting assisted reproductive treatments, and has the greatest benefit for those who have experienced repeated implantation failure.

Although the endometrial receptivity analysis is indicated for all the patients starting assisted reproductive treatments, is highly recommended if you’ve undergone two or more IVF cycles that were not successful, where the embryos were of good quality. If you have had two miscarriages or more, you may want to ask your doctor if Pre-implantation Genetic Testing for the Aneuploidy (previously known as PGS) is something that they suggest, as it can help increase the chances of having a healthy baby and decrease your chances of a miscarriage.

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