Endometrial Receptivity Array Test (ERA test)

What is endometrial receptivity testing in IVF?

• Embryo transfer is usually performed at the same time of the cycle for all patients, when the lining of the uterus (endometrium) is thought to be ready or able to have an embryo attach (implant) into it. This is called ‘standard timing’.
• The period of time during a cycle when the endometrium is receptive is known as the 'window of implantation,' and is typically around three days long. The ‘receptivity’ of the endometrium means whether the endometrium is able to allow an embryo to attach (implant) into it.
• Endometrial receptivity testing aims to determine the implantation window for frozen embryo transfer for a specific person. It requires taking a biopsy of the endometrium and analysing the endometrial tissue to work out whether the endometrium is receptive or not.
• Because the test result suggests that timing of the embryo transfer might be different for different people, this is sometimes called ‘personalised embryo transfer’.
• The most used endometrial receptivity test in Australia is the Endometrial Receptivity Array test (ERA test).

Other brands of endometrial receptivity tests may also be available in Australia, such as ERPeak. However, none of these have been evaluated in a randomised controlled trial (the highest level of evidence), therefore this page focusses on the ERA test.

Why might the ERA test improve IVF outcomes?

• Some research has suggested that the implantation window might be different in different people. For some people it might be earlier or later than usual (i.e. standard timing).
• People with a window of implantation that does not match standard timing of embryo transfer, could benefit from having an embryo transfer either earlier or later than usual.

Why might the ERA test not improve IVF outcomes?

• An endometrial biopsy might not collect a balanced mix of cell types, which could affect the results. The endometrium is made up of many different types of cells. Different types of cells may turn on some genes and not others, creating different gene expression patterns. If gene expression levels seem higher or lower than expected, it might simply be because the sample happened to include more of one type of cell, rather than indicating a real change in the implantation window.
• The window of implantation can vary from month to month. Testing it in one cycle and applying the results to a different cycle assumes it stays the same, but that might not always be true.
• It is important to remember that most embryo transfers don’t result in pregnancy. Implantation failure can occur for many different reasons that have nothing to do with the window of implantation or timing of the embryo transfer. Most of the time when embryos fail to implant it is due to genetic or chromosomal problems in the embryo itself. Therefore, changing the timing of embryo transfer may not be expected to make much difference to the chance of successful implantation.

Who might consider the ERA test for IVF?

People who have experienced repeated implantation failure

Does the ERA test for IVF work? What the evidence says

Endometrial receptivity testing with the endometrial receptivity array (ERA test) does not appear to affect the chance of getting pregnant and having a baby from IVF. Only two trials were available. The evidence is judged as low to moderate quality, as although the test is commonly offered to patients with recurrent implantation failure, the two available trials both excluded patients with previous implantation failures.

Side effects of the ERA test

Side effects of endometrial biopsy:

• The most common side effect is pain - studies report pain scores of around 4 out of 10.
• Rare side effects include:
  • Prolonged bleeding from the vagina
  • Infection in the uterus
  • Uterine perforation (making a hole in the wall of the uterus) but this is extremely rare
  • Feeling faint for a short time during and after the procedure
  • Endometrial adhesions, which are more likely if infection occurs. These may require further treatment and could make it more difficult to get pregnant. However, this is very rare.

All medical procedures carry some risk.

The procedure used to obtain the endometrial tissue is called an endometrial or pipelle biopsy. The procedure is considered safe and serious complications are rare.

• In some cases, the biopsy may be collected as part of a surgical procedure, such as a hysteroscopy, which has its own, separate risks. A hysteroscopy is a surgical procedure where an instrument is inserted through the vagina and cervix so the doctor can look inside the uterus. This may be performed under a general anaesthetic.

Risks of the ERA test and long-term outcomes

There are no known risks or long-term harms

• This is based on data from randomised controlled trials and input from IVF specialists. Possible risks of harm and long-term outcomes are often not reported in randomised trials and therefore it is unknown whether endometrial receptivity testing with ERA or other tests poses any risk of harm to the IVF patient or the embryo/baby.

ERA has been used in Australia since 2013, and approximately 2,000 IVF cycles have used ERA testing.

Cost of the Endometrial Receptivity Array test (ERA test)

The ERA test for IVF usually costs between $1500 - $2,500 AUD (including the cost of the appointment to undergo the ERA biopsy). Most people will only have one ERA test performed. At times, the biopsy may be collected as part of another procedure, such as a hysteroscopy which is a procedure to look inside the uterus, and this may incur additional costs.

Cost information is indicative only, costs can vary from clinic to clinic and depending on different circumstances.

Practical considerations about ERA testing

• The ERA test in IVF requires an endometrial biopsy to be taken in an ‘ERA cycle’. This usually means that IVF patients will need to freeze their embryos and undergo their embryo transfer as a frozen cycle (rather than have a fresh embryo transfer). It also means that the embryo transfer will be delayed by 1-2 months while awaiting the results of the test.
• In approximately 5% of patients, the biopsy result will be inconclusive and a second biopsy may be suggested.
• The biopsy procedure required for the ERA test may require an additional visit to the IVF clinic. If the biopsy is undertaken as part of hysteroscopy procedure, it may require a hospital admission.

Unsure about some of the terms we have used? Use our glossary to understand scientific or unfamiliar terms.