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Useful facts about the endometrial receptivity array (era) test

Test era Daniel Sosa

The ERA test (Endometrial Receptivity Array) is a diagnostic test which allows us to study the endometrium to see if it is in a suitable condition for embryo implantation to occur. One of the causes that is a limiting factor in the success of assisted reproduction treatments is implantation failure. According to the European Society of Human Reproduction and Embryology (ESHRE) “Implantation failure occurs after ≥3 good quality embryo transfers, from an IVF or oocyte donation cycle, in women under 37 years of age or ≥2 in women over 37 years of age”.

Once this diagnosis has been made, the assisted reproduction specialist will indicate a series of studies, designed to obtain more information as to why the failure is occurring.

Thanks to the ERA test we can study the state of the endometrium in detail. As medical director Dr. Daniel Sosa explains; with the endometrial receptivity test we can personalize the embryo transfer. In this way the assisted reproduction treatment can performed in the most suitable moment for each woman.

Dr. Sosa also points out that the patient is less likely to suffer implantation failure with this test. The embryo transfer needs to be done in what is known as “the implantation window”, when endometrial receptivity is optimal to allow embryo implantation to occur. In natural cycles this is usually between five and seven days after ovulation. For Dr. Sosa, the ERA test is not only important for embryo implantation into the uterus, but also can help identify any possible fertility problems.


As we have discussed, the endometrial receptivity array test, ERA test, is the base for analyzing the condition of your endometrium, which is referred to as receptivity. Indeed, with the information received from the ERA test, the embryo transfer can be programmed for the best moment to increase the probability of pregnancy.

To follow, Dr. Sosa explains what happens in each step:


The ERA test is carried out following these steps:

  1. A sample of the woman’s endometrial tissue is obtained by means of an endometrial biopsy.
  2. This endometrial tissue is placed into an appropriate, sterile vessel.
  3. The sample is maintained at a low temperature and sent for analysis.

Although the biopsy procedure is a simple one, we always advise our patients that it may produce some discomfort. An operating theatre and anesthesia are not required, but we can give mild sedation for the more apprehensive patients.


Dr. Sosa, as a specialist medical fertility expert, recommends this test if you have suffered implantation failures in an in vitro fertilization or egg donation treatment. The ERA test is also very important if you have had failures after the transfer of good quality embryos, and especially if you they were embryos which had undergone pre implantation genetic testing (PGD).


According to Ovoclinic’s medical director, Dr, Daniel Sosa, the correct moment to do the endometrial biopsy can depend on whether the woman is undergoing a hormonal treatment or not.

If the patient is having hormonal treatment to prepare the endometrium, the biopsy will be done after 5 days. This is to say 120 hours after starting the doses of progesterone, on day P+5.

In the case that the patient is in a natural cycle, the endometrial sample should be taken 7 days after the LH surge has been detected. In medical jargon this is termed day LH+7. In many cases this LH surge is achieved artificially with an ovulation inducing medication.

In a previous article about ovulation tests, we explain how the levels of LH hormone rise before ovulation, triggering the release of the egg and along with it an increase of progesterone, thus preparing the endometrium to become receptive.


The endometrial receptivity array test uses a massive genetic sequencing to analyze 238 genes involved in the control of normal endometrial receptivity. In the cycle in which the endometrial biopsy is taken, the team of fertility specialists will also investigate endometrial growth, medication dose and the time the endometrium takes to reach the required thickness and appearance.


There can be two different results from the ERA:

  • Receptive: the implantation window corresponds with the day the biopsy was performed. This is the therefore the optimum moment in the cycle to program the embryo transfer.
  • Non-receptive: the day of the embryo biopsy does not correspond with the implantation window. This means that this window is displaced, which can be a sign of infertility problems. Usually, the laboratory report will inform if the biopsy was done before or after the implantation window. In many cases they may also suggest if the transfer should be performed a determined number of hours before or after the 120 hours in cycles with hormonal treatment


At Ovoclinic, we explain to all our patients that if having the ERA test, we need to know the results of the test in order to do the embryo transfer, and as such the embryo transfer has to be delayed until the next cycle.

If the result was RECEPTIVE, the embryo transfer will be programmed for the same conditions which were used to take the biopsy.

If the result was NON RECEPTIVE, the embryo transfer will be scheduled according to the recommendations of the biopsy laboratory, respecting the most suitable moment for transfer to achieve the best results for the patient.

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