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Many women undergoing IVF are unable to get pregnant, even after transferring good quality embryos. Although a good quality embryo is an important starting point, it is also important to transfer the embryo into a uterus that is ready to receive the embryo.


The timing of embryo transfer must be coordinated with your body’s menstrual cycle, neither too early nor too late, but at just the right time. For most women, the best time to transfer an embryo is the same, but for 30% of women, this optimal window is displaced.

What is ERA test?

ERA evaluates endometrial receptivity to determine the optimal time for embryo transfer.

What is the endometrium?

The interior of the uterus is lined with a tissue called endometrium, which is prepared each month for the arrival of an embryo and it’s the nest where the embryo implants and resides during gestation. Even the best embryo will fail to implant if conditions aren’t right.





What is Endometrial receptivity?

The endometrium is receptive when it is ready for embryo implantation to occur. This period of receptivity is called the window of implantation.

Each woman has a unique window. For some women the window is shorter and/or displaced. By knowing your personal window of implantation, you can optimize your chances of pregnancy through a personalized embryo transfer.

ERA uses the principle of endometrium will be ready for embryo implantation after 5 full days with Progesterone administration. ERA use biopsy, endometrium tissue  to analyze gene expression to find the precise time for embryo transfer. Increases the chances of implantation of the embryo, which will eventually lead to pregnancy.

Embryo conditions for ERA process

This is because the results of ERA TEST will only be used to calculate the optimal interval of Endometrial Receptivity, not related to the embryo. The embryo that will be used for transfer should be characteristics that favor the chances of pregnancy as follows:

1. The embryo must be mature enough to successfully implant (it must have reached the blastocyst stage, which is day 5 or 6 of growth).

2. The embryo should be chromosomally normal so that it can implant and lead to an ongoing pregnancy (abnormal embryos will usually fail to implant or result in a miscarriage.)


If both the embryo and uterus are ready at the same time, implantation and pregnancy can occur; if the window is missed, however, and the embryo is not at the right developmental stage by the time it reaches the uterus, it doesn’t contain the right number of chromosomes or the endometrium is not expressing the correct genes, implantation and pregnancy will not occur.


Indications for ERA

  • The ERA is indicated for recurrent implantation failure (RIF) patients, since they have a higher risk of having a displaced window if implantation.

  • In case the patient requires any intervention at uterine level, the ERA test must be done after such intervention in order to replicate as much as possible the conditions in which the embryo transfer will take place.

  • Endometrium should be thick at least 6mm, in case of atrophic (< 6mm) or hypertrophic endometrium (>12mm), the ERA can be done if this condition is constant in all endometrium cycles for this patient.

How does the ERA test work?

The test consists of two parts:

  • Taking a sample of endometrium (a biopsy)

The biopsy is usually performed at the exact moment when doctors would transfer an embryo into a patient’s uterus. This means that patients will undergo a transfer cycle but not actually have the embryo transferred. This is because the objective is to test the endometrium for its gene expression right before a transfer.


This ‘prep’ cycle involves the same steps as a ‘real’ transfer cycle. – taking oral medications and self-injected medications to stimulate your uterine lining. This prep cycle will require transvaginal ultrasounds and bloodwork visits to monitor response to the medications.


At the end of the prep cycle, a doctor will perform the biopsy. The biopsy is about 3 minutes procedure that may be slightly uncomfortable. The procedure does not require sedation.


The biopsy involves placing a flexible plastic tube into the woman’s uterus (with the help of a vaginal speculum) and moving it back and forth to collect tissue from the lining of the uterus.


  • Having that sample tested for its gene expression

The biopsy sample will be used Next Generation Sequencing (NGS) technology to analyze the gene expression of 248 genes related with the endometrial receptive status.

Depending on the result, a doctor may move the patient’s transfer timing (by modifying the patient’s exposure to progesterone) forward or back so the patient can try to meet her window of receptivity during her next cycle.


Benefits of ERA

  • When performing a personalized embryo transfer, the likelihood of getting pregnant in assisted reproduction treatment is increased

  • 72.5%* pregnancy rate using ERA in the first IVF cycle in any patient.

  • Maximize your chances of pregnancy without losing good embryos

  • Decrease recurrent implantation failure (RIF)


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