Endometrial Receptivity Analysis (ERA) The Importance of Timing Accuracy

In every IVF cycle, the timing of embryo implantation is one of the most crucial factors for success. It's not enough for the embryo to be of good quality and the uterus to be healthy. Implantation success also depends on the receptivity of the endometrium during the window of implantation (WOI). The ERA test is an advanced diagnostic tool designed to answer this exact question: when is the most appropriate time for embryo transfer?

What Is the ERA Test

The ERA (Endometrial Receptivity Analysis) is a molecular test that evaluates the functionality of the endometrium by analyzing the expression of hundreds of genes related to its receptivity. It is a highly accurate tool that allows specialists to determine whether the endometrium was receptive or not at the time of biopsy.

This means we can identify the so-called implantation window (WOI) in a personalized manner and adjust the timing of the embryo transfer to match each woman’s specific needs—maximizing the chances of success.

Why Is the ERA Test Recommended

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In many cases where everything seems to be in order—the quality of the eggs is satisfactory, the uterus appears normal, and the embryo is healthy—pregnancy still does not occur. One possible reason under investigation is that the embryo transfer may be happening outside the ideal implantation window. The ERA is mainly recommended for women who have experienced repeated implantation failures (RIF) in IVF cycles without any other apparent cause. In such cases, investigating the timing of implantation often reveals critical information that helps refine the treatment strategy.

How the ERA Test Is Performed

The process involves preparing the endometrium using the same medication protocol that the woman would receive in an embryo transfer cycle. On the appropriate day—based on the number of days of progesterone administration—a biopsy of the endometrium is taken.The sample is sent to a specialized laboratory where the gene expression profile is analyzed.

The results show whether the endometrium was:

In the receptive phase – meaning the implantation window occurred at the time of biopsy

In the pre-receptive or post-receptive phase – meaning the implantation window lies at a different time point

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What Is the Importance of the ERA Test Result

The significance of the ERA result lies in the ability to accurately plan the next embryo transfer. If the endometrium is found to be pre-receptive, progesterone will be administered for more days. If it is post-receptive, fewer days of progesterone will be given. In this way, endometrial receptivity is assessed, and the timing of embryo transfer is tailored—not based on general guidelines, but on the specific needs of each woman’s endometrium.

The Use of the ERA Test by the Scientific Community

Although the ERA is not a routine diagnostic test for all IVF cycles, several studies confirm its value in cases of unexplained implantation failure, when everything else appears normal. Its use has been associated with improved success rates in women with a displaced implantation window. However, it is essential to apply the test with clinical judgment, as part of a comprehensive and personalized evaluation.

FertUlity’s Approach

At FertUlity, we carefully evaluate which couples or women can truly benefit from the ERA test. We do not rely on standardized protocols but approach each case holistically.When indicated, we combine ERA with other endometrial tests (e.g., ALICE, EMMA) to accurately map the microbial and inflammatory status of the uterine lining.

Our goal is not just to transfer an embryo, but to transfer it at the right time, in the right environment, with the highest chances of success.If you’ve experienced implantation failures without a clear cause, ERA may be the next step toward a more targeted and personalized treatment approach.

Frequently Asked Questions About ERA Test

When is it recommended to do the ERA test?

ERA is mainly recommended for women who have experienced two or more failed embryo transfers (RIF) with good-quality embryos and no identifiable cause. In such cases, assessing endometrial receptivity at the time of transfer can be a key factor.

Does the ERA biopsy hurt?

The endometrial biopsy experience is similar to that of a Pap smear. It may cause brief and mild discomfort, but the procedure only takes a few minutes and does not require anesthesia or hospitalization.

Are there any side effects?

ERA is a safe procedure with minimal side effects. Some women may experience light bleeding or cramping for a few hours after the biopsy.

If the result shows I’m “pre-receptive,” what does that mean for my next IVF cycle?

If the result shows that the endometrium was not yet receptive, the next embryo transfer cycle will be scheduled with additional days of progesterone to align the transfer with
the optimal implantation window.

Do I need to do ERA in every cycle?

No, once the ideal implantation window has been identified, the results are valid for future cycles with a similar hormonal protocol. The test does not need to be repeated unless there is a significant change in protocol or endometrial condition.

Our Doctors

In an era where fertility requires knowledge, care, and substantial guidance, FertUlity is not an impersonal clinic. It is two people who look you in the eye and accompany you step by step on the journey you dream of.

Dr. Maria Oikonomou Obstetrician – Gynecologist

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Dr. Chrysostomos (Makis) Papadopoulos Obstetrician – Gynecologist, MD, PhDc, MIC I

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