Endometrial Receptivity Analysis (ERA)

Stress and anxiety from repeated implantation failure (RIF) are daunting emotions that couples undergoing IVF must contend with. Advanced diagnostic technology, like Endometrial Receptivity Analysis (ERA), can improve the chance of successful conception for couples with infertility.

What is ERA?

Endometrial Receptivity Analysis (ERA) is a test to measure the thickness of the uterine lining and genetic variations to assess whether the endometrium is sufficiently ripe for embryo implantation. ERA can determine the ideal timing for progesterone administration before an embryo transfer to enhance the success of embryo implantation, pregnancy, and live birth since successful implantation can only occur during the window of receptivity.

What is endometrium?

The endometrium is a lining tissue of the uterine cavity. The lining consists of two layers -- the stratum basalis situated adjacent to the smooth muscle layer, which persists through the menstrual cycle without shedding, and the stratum functionals, which thickens and sheds during menstruation. 

Estrogen and progesterone regulate the growth of the endometrium. The hormones help thicken the endometrial layers to prepare the uterus for embryo implantation. 

What is endometrial receptivity?

Endometrial receptivity occurs when the uterine lining is of sufficient thickness for embryo implantation and the nourishment of a developing embryo. The endometrial receptivity or window of receptivity is brief and transient.

Between days 20 and 24 of a regular 28-day menstrual cycle, there will be changes in gene expression, secretion of molecules, and structural modifications of the endometrium to support embryo implantation. For successful implantation, the embryo must reach a day 5 or 6 blastocysts with a regular complement of chromosomes (euploidy). Abnormal embryos (aneuploid) will fail to implant or suffer an early miscarriage.

Pregnancy will fail under the following conditions:

• Missed window of receptivity
• The embryo does not develop sufficiently for implantation.
• The embryo harbors chromosomal abnormalities.
• The endometrium fails to activate and express the appropriate genes or is not in a receptive state.

This window of receptivity is relevant to both natural conception and in vitro fertilization (IVF). It varies for everyone depending on the progesterone level and the gene expression profiles of the endometrium.

At what point during IVF should women undergo ERA testing?

Endometrial Receptivity Analysis (ERA) is beneficial for women with a history of recurrent implantation failure or multiple unsuccessful IVF cycles. ERA allows the determination of 236-gene array expressions to pinpoint the optimal receptivity window for embryo implantation. The precise timing enhances the likelihood of a successful pregnancy, with the ideal window falling between the 19th and 23rd day of her cycle in 80% of women; however, the remaining 20% may have an earlier or later window of receptivity. The capability to determine whether the receptivity window is open or closed is crucial before embryo transfer in IVF treatment.

What are the procedural steps of ERA?

• Take the prescribed oral or self-injected medications to stimulate the growth of the uterine lining and monitor with transvaginal ultrasounds and blood tests for the response.
• The doctor performs an endometrial biopsy to determine the gene expression profile of a panel of genes.
• Based on the biopsy result, the doctor will assess whether the endometrium is receptive or non-receptive for embryo implantation.
• In the event of non-receptivity, the doctor will postpone the embryo transfer to the next cycle and adjust the progesterone doses to increase the likelihood of a successful pregnancy.

What are the possible ERA test outcomes?

The ERA test can yield three types of results:

• Receptive result: This indicates that the endometrium is in an optimal state for embryo implantation, and the patient received the appropriate amount of progesterone exposure. The endometrium is ready for embryo transfer.
• Pre-receptive result: The patient did not receive sufficient progesterone; therefore, an endometrium is not receptive to the embryo. An additional progesterone exposure of 12 or 24 hours is necessary before an embryo transfer.
• Post-receptive result: The patient received progesterone too early in the menstrual cycle. A repeat biopsy is necessary to determine the correct timing of progesterone initiation.

In rare instances, the result may be inconclusive.

Note from MedPark's Doctor

Struggling to conceive can be a frustrating and isolating experience. At MedPark Hospital, we understand the challenges you face. Our team of experienced reproductive gynecologists is dedicated to helping you build your family. We offer personalized fertility treatments based on your unique medical history and needs.

If you're ready to explore your options, contact MedPark IVF – Fertility and Genetics Center at Tel. 02-090-3020. 

We're here to support you on your journey to parenthood.