Endometrial Receptivity Array (ERA)

Your endometrium is the inner lining of your uterus where your embryo will implant and develop during your pregnancy. The endometrium lining keeps changing throughout your menstrual cycle in response to hormones such as estrogen and progesterone and typically reaches an optimal thickness and receptiveness around the time of your ovulation to support implantation. For pregnancy to happen, the embryo must successfully attach to a healthy endometrium.

What is Endometrial Receptivity?

Endometrial receptivity is the ability of the uterine lining to permit an embryo to attach (implant) successfully. Endometrial receptivity has a distinct time window called the window of implantation which typically opens a few days post-ovulation or progesterone exposure. For most women, this window happens at a predictable time, but for others the window is shifted and thus an early or late transfer can result in poor implantation chances even with good quality embryos.

What is an ERA Test?

The ERA test which is also known as the Endometrial Receptivity Array is a diagnostic test that examines the genetic activity of the endometrium to find out whether it is ready for embryo implantation.

Unlike ultrasound scans, which assess the thickness and appearance of the uterine lining, the endometrial receptivity array test examines the expression of hundreds of genes associated with implantation. This helps identify whether the endometrium is receptive at the time of testing.

ERA Test in IVF

The ERA test, as part of the IVF process, is usually performed during a mock embryo transfer cycle. A sample of the endometrial tissue is collected and sent for analysis at a specialised laboratory. Once the results are obtained, they help fertility specialists make a decision about when the embryo transfer will take place or if there is a need for customisation of timing corresponding to the patient’s specific implantation window.

How Does ERA Work?

The Endometrial Receptivity Array (ERA) analyses the activity of genes involved in embryo implantation to determine whether the uterine lining is ready to receive an embryo. During the ERA procedure, a small endometrial sample is collected through an ERA biopsy and sent to a specialised laboratory for analysis.

By evaluating gene expression patterns, the endometrial receptivity array test helps identify a woman’s unique window of implantation, allowing fertility specialists to personalise the timing of embryo transfer when needed.

Why is the ERA Test Done?

The main purpose of the ERA test is to determine the most appropriate time to transfer your embryo to the uterus.

Your embryos need to be of good quality, however it also relies on the receptiveness of the endometrial lining. The test helps determine whether the endometrium is receptive when the embryo transfer is planned.

An ERA may be recommended to:

• Investigate possible implantation-related issues
• Identify a displaced window of implantation
• Personalise embryo transfer timing
• Improve treatment planning in selected IVF patients
• Provide additional information after unsuccessful IVF cycles

Who Needs an ERA Test?

The ERA test is only advised in certain cases and not everyone undergoing IVF is advised to undergo this test. Your fertility specialist may suggest an ERA test if you:

• Have experienced recurrent implantation failure
• Have had multiple unsuccessful IVF cycles despite good-quality embryos
• Have undergone transfers of genetically tested embryos without pregnancy
• Have unexplained repeated embryo transfer failures
• Wish to explore personalised embryo transfer strategies

At What Point During IVF Should Women Undergo ERA Testing?

The ERA test procedure is often completed prior to the actual embryo transfer cycle. Most fertility clinics do this during a mock cycle, which closely resembles the hormonal preparation required for a frozen embryo transfer. This allows the endometrium to develop under conditions similar to those planned for the actual IVF treatment.

The information gained from the ERA test is then utilised when preparing for the actual future embryo transfer cycle.

ERA Test Procedure: Step by Step

Understanding the ERA procedure can help reduce anxiety and prepare you for what to expect.

Step 1: Endometrial Preparation

The process starts with preparing the uterine lining with the help of hormones. Based on your treatment plan, you may be suggested orstrogen and progesterone medicines to mimic the conditions of an IVF cycle.

The timing of progesterone exposure plays a critical role in determining the receptivity of endometrium, therefore, it is carefully monitored.

Step 2: Endometrial Biopsy

An ERA biopsy is performed after the uterine lining is prepared. A thin catheter is gently inserted through the cervix to collect a small sample of endometrial tissue. The procedure is usually completed within a few minutes and is performed without general anaesthesia.

Some women may experience the following symptoms which usually resolve in 1-2 days.

• Mild cramping
• Temporary pelvic discomfort
• Light spotting after the procedure

Step 3: Genetic Analysis

The biopsy sample is sent to a specialised laboratory for analysis.

Scientists evaluate the activity of hundreds of genes associated with implantation. The genetic profile helps determine whether the endometrium is receptive or non-receptive at the time the sample was collected.

Step 4: Report Generation

The laboratory generates a detailed report that identifies the receptivity status of the endometrium.

Based on these findings, your fertility specialist can recommend the most appropriate timing for embryo transfer in future treatment cycles.