Endometrial Receptivity
Analysis (ERA)

ERA determines the optimal window of implantation (WOI) to transfer an embryo into a woman’s uterus. This involves taking a biopsy of the endometrial lining of the uterus and testing genetic variants to assess whether the endometrium is adequately mature for embryo implantation.

What is Endometrium?

It is the inner lining of the uterus where a fertilized egg is implanted. It consists of two layers: the stratum basalis that attaches to the smooth muscle tissue of your uterus, and the stratum functionals that shred during menstruation.

Estradiol and progesterone control the growth of the endometrium. The ovaries are the principal source of these two hormones, which help thicken the endometrial layers to prepare the uterus for embryo implantation.

What is Endometrial Receptivity?

This happens when the uterine lining is thick enough for the embryo to attach and develop a new individual. The window of implantation (WOI) normally extends 3 to 6 days within the secretory phase. A successful implantation requires a day 5 or 6 blastocysts with a normal chromosome complement (euploidy), whereas abnormal embryos (aneuploid) result in failed implantation or miscarriage.

When should you undergo ERA Testing?

If the endometrium isn’t receptive at the time of transfer, implantation is unlikely to occur. Women with repeated failed IVF cycles may benefit from an ERA test.

After two or more failed IVF cycles despite transferring good-quality embryos
When egg quality, sperm quality, embryo development, and uterine anatomy appear normal
For women over 35 looking to reduce the risk of another unsuccessful transfer
When using donor eggs or embryos, where embryo quality is already well-established

How Effective is ERA?

By identifying the optimal time of implantation, ERA minimizes implantation failure. Some studies showed an improvement in female fertility by using ERA before their implantation. The test can also offer clarity and direction when women have experienced recurrent implantation failure. It provides the following benefits:

Tailored embryo transfer – Pinpoints the best time for implantation based on your endometrial profile.
Higher success potential – Boost implantation and pregnancy rates for certain patients.
Fewer unsuccessful attempts – Helps avoid transfers during non-receptive periods.
Peace of mind – Offers relief when standard fertility tests are unreliable.

What are the procedural steps of ERA?

Take the prescribed medications to stimulate growth of the uterine lining and monitor with transvaginal ultrasounds.

The doctor performs an endometrial biopsy to determine gene expression profile.

Based on the biopsy results, the doctor determines whether the endometrium is receptive or non-receptive.

If it is non-receptive, the doctor will postpone the embryo transfer to the next cycle to adjust the progesterone for a higher pregnancy rate.

What are the possible ERA test outcomes?

Receptive Result: The WOI is open at the time and the endometrium is ready for an embryo transfer. This means that the patient received the appropriate amount of progesterone exposure.
Non-receptive Result: The endometrium is not ready for an embryo transfer due to insufficient progesterone exposure. An extra 12 to 24 hours of progesterone exposure is required before proceeding with the transfer.
Post-receptive Result: When a progesterone started too early in the menstrual cycle, a repeated biopsy is necessary to identify the correct timing of progesterone initiation.

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