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Endometrial receptivity array (ERA)

Treatment add-on with limited evidence

For most patients, having a routine cycle of proven fertility treatment is effective without using any treatment add-ons.

Red traffic light

Red

The use of ERA as part of fertility treatment in healthy patients is rated red. This is because there is no evidence from randomised controlled trials (RCTs) to show that they are effective at improving the chances of having a baby for most fertility patients.

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What does this traffic light rating mean?

Our traffic-light rated list of add-ons consists of three colours that indicate whether the evidence, in the form of high-quality RCTs, shows that a treatment add-on is effective at improving the chances of having a baby for most fertility patients.

We give a red symbol for an add-on where there is no evidence from RCTs to show that it is effective at improving your chances of having a baby for most fertility patients.

The January 2019 consensus statement (PDF) between the HFEA and ten other professional and patient bodies agreed that treatments that have no strong evidence of their safety and/or effectiveness should only be offered in a research setting. Patients should not be charged extra to take part in research, including clinical trials.

For specific patient groups there may be reasons for the use of a treatment add-on other than improving your chances of having a baby. In these situations, it may be appropriate for you to be offered a treatment add-on as part of your treatment and not in a research setting.

Our traffic light ratings only indicate the effectiveness of a treatment add-on at improving your chances of having a baby. Specific safety concerns about a treatment add-on are included under the dedicated section ‘Is this treatment add-on safe?’

What is endometrial receptivity array?

Endometrial receptivity array (ERA) is a test that claims to find the optimal time for an embryo to be transferred into a woman’s uterus for the embryo to implant, known as the window of implantation. ERA involves taking a biopsy of the endometrial lining of the uterus and testing the tissue to see which genes are expressed. When combined with a computational predictor these results indicate when the endometrium may be most receptive to an embryo implanting. The endometrium will be categorised as either receptive, pre-receptive, or post-receptive.

In subsequent cycles of treatment, the patient will then have what is termed a ‘personalised embryo transfer’, taking place at the optimal time for her specific window of implantation. This would theoretically increase the chances of the embryo implanting successfully and the patient having a baby. However, there is a question over whether a patient has the same window of implantation for each of their cycles of treatment.

You can read more about how ERA works in the meeting papers of the June 2021 Scientific and Clinical Advances Advisory Committee (SCAAC) meeting where the application for this treatment to be added to the HFEA’s traffic light rated list of add-ons was considered.

What’s the evidence for ERA?

One RCT has been performed to study the effectiveness of ERA at increasing a patient’s chances of having a baby. The outcomes of the study were promising but the results did not prove that ERA made a true difference to the patient’s chances of having a baby and we can’t be certain of their reliability.

At the October 2021 SCAAC meeting the Committee evaluated the evidence base for ERA. Minutes of this discussion and the evidence used to inform this discussion are available on the SCAAC webpage.

Is this treatment add-on safe?

As this procedure requires obtaining a biopsy of the endometrium patients can experience cramping and there is a small risk of infection and bleeding. There is also a very small chance of uterine perforation. The biopsy may need to be repeated in the rare event that either the results are inconclusive, or the biopsy fails to obtain a sufficient quantity or quality of tissue for testing.

ERA requires patients to undergo a freeze-all cycle which carries a small risk that any frozen embryos would not survive the thawing process. ERA does not carry any additional known risks for the child born as a result of fertility treatment.

If you have any questions about the safety and risks, your clinic will be able to discuss whether a treatment add-on would be safe for you to use considering your specific medical history and circumstances.

What are treatment add-ons?

  • optional additional treatments, also referred to as ‘supplementary’, ‘adjuvants’ or ‘embryology treatments’.
  • often claim to be effective at improving the chances of having a baby (live birth rate) but the evidence to support this for most fertility patients is usually missing or not very reliable.
  • likely to involve an additional cost on top of the cost of a routine cycle of proven fertility treatment. Some treatment add-ons can cost hundreds or thousands of pounds each.

It is important to keep in mind that for most patients, having a routine cycle of proven fertility treatment is effective without using any treatment add-ons. If you are paying directly for your own treatment, you may want to think about whether it might be more effective and/or affordable to pay for multiple routine proven treatment cycles, rather than spending large sums of money on a single treatment cycle with treatment add-ons that haven’t been proven to be effective at increasing the likelihood of you having a baby.

We aim to publish clear and reliable information about some of the treatment add-ons that don’t have enough evidence, from high-quality randomised control trials (RCTs), to show that they are effective at improving your chances of having a baby.

To make it easier to understand the scientific evidence for each treatment add-on we have developed our traffic-light rated list of add-ons.

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Review date: 4 January 2024