What is Endometrial Receptor Array testing?
ERA is a pioneering new method of assessing when the endometrium is at its most receptive in a patient in order to inform the clinician as to the optimal time to replace embryos in fertility treatment. In effect, this gives personalised embryo transfer timing (pET).The procedure involves testing a sample of the lining of the womb to identify more than 240 genes that indicate whether the patients “implantation window” is open, and that the lining of the womb is receptive to allow the embryo to implant.
Who should consider this test?
This test is not advised for all patients. We only recommend consideration of this test in cases of recurrent implantation failure, that is when the patient has failed to achieve a pregnancy in spite of the transfer of good quality day 5 embryos on three or more occasions if under 37 years of age or two occasions if over 37. This is especially true for patients who may still have embryos in cryopreservation awaiting transfer. Your clinician can advise you if they feel that this test may benefit your treatment.
What is the implantation window?
The implantation window is a narrow point in the menstrual cycle (or treatment cycle) when the endometrium is receptive to allow the implantation of the embryo. Traditionally the implantation window is thought to be a fixed time around 7-9 days after the natural surge of hormones that trigger ovulation (or the trigger injection used in fertility treatment cycles. Therefore blastocyst (day 5) embryos are transferred 5 days after egg collection or at a fixed time in a frozen cycle (7 days after the natural hormone surge or 5 days after starting progesterone). The ERA test seems to show that in some individuals, the implantation window may open and close earlier, (post receptive) or later (pre receptive) than traditionally thought. Outside of these times, the endometrium is less receptive and more hostile to embryos thus preventing implantation and pregnancy.
What does the test show?
This test is designed to detect the specific genes that are thought to be associated with the opening and closing of the implantation window and those that are most expressed when the endometrium is at its most receptive. A report is produced to show whether the endometrium is ‘Receptive’ (R) or ‘Non Receptive’ (NR). Clinicians can therefore adjust the timing of the replacement of embryos to ensure that an embryo is placed into the uterus at the time when the endometrium is ‘Receptive’, and most likely to allow the embryo to implant and create a successful pregnancy. If the result is ‘Non Receptive’ a second biopsy is usually recommended at a different point in the following cycle to allow exact identification of the patients receptive window.
How many patients have an abnormal / displaced implantation window?
Research has shown that in specific patients with previous failed embryo transfers or recurrent implantation failure (transfer of three good quality embryos if under 37 years of age, or two transfers if over 37 years of age) and with a normal development of the endometrium on ultrasound (>6.5mm) then 24% of patients undergoing this test show a displaced implantation window or ‘Non Receptive’ endometrium. Of these patients with a ‘Non Receptive’ endometrium, 80% indicate that a transfer later in the cycle is more appropriate and 20% indicate that an earlier embryo transfer is more appropriate.
What is the evidence for this test?
This test has taken more than 10 years to develop and studies have been published and presented to show its benefits. Most studies are small but show significant benefit, and so currently a very large study is being conducted across Europe. Published studies have shown that when endometrial receptivity array indicates a ‘Receptive’ endometrium, subsequent implantation and pregnancy rates are reassuringly high. For patients with recurrent implantation failure (average of 4.5 previous transfers) and a ‘Non Receptive’ endometrium, using a pET in subsequent cycles gave them an increased chance of pregnancy.
How is the test done?
The test is performed by taking a small biopsy from the endometrium. This is performed by passing a small tube through the cervix and aspirating some of the tissue from the womb. This process is the same as used when performing an endometrial scratch. The sample is then chilled for four hours in a special solution before it is couriered to the iGenomix laboratory.
When can the test be performed?
This test has to be performed in a cycle preceding any planned treatment cycle. For patients who are having this test as part of investigation of recurrent pregnancy loss then a natural cycle can be followed. For patients who are ovulating normally as detected by ovulation kits, it is performed five days (or approximately 120 hours) after the detection of the natural hormone ovulation surge. We will usually advise patients to check for surge once per day, first urine sample in the morning. If patients are having this test due to recurrent implantation failure then a mock cycle using oestrogen and progesterone is given, to reflect the same process and hormone levels as would be present during a treatment cycle, and the biopsy is taken five days after starting the progesterone pessaries.
How long does it take to get the results?
The results will be returned to the clinic within 15 days, and so the timing of embryo replacement will be known in the next cycle unless a second biopsy is recommended.
Are there any risks?
The endometrial biopsy is an essentially low risk procedure that is used in many aspects of gynaecology. There is evidence both for and against the use of this test however, all patients undergoing fertility treatment at North West Fertility will be advised if the clinician feels it would be of benefit. There is a small chance (5%) that the biopsy may not be adequate, or the tissue is unsuitable for processing in which case the test will be repeated at no extra charge in your next cycle.
What should I do if I want this test?
Before deciding on going ahead with this test it is important to have a full discussion with a fertility specialist to look at all aspects of recurrent implantation failure. Your clinician will carefully discuss the implications, benefits and risks. If you decide to go ahead, your clinician will organise the appropriate consents and arrange the collection, processing and transport of the biopsy.
