What is endometrial receptivity?

The endometrium is the lining the interior of the uterus where the embryo implants and resides during pregnancy. The endometrium is receptive when it is ready for embryo implantation.

What is window of implantation (WOI)?

The endometrium is receptive when it is ready for embryo implantation. This period of receptivity is called the window of implantation.

Defining a receptive window would avoid embryo wastage and emotional, physical, and financial distress. Approximately 3 in every 10 women have a displaced window of implantation.

What is the ERA test?

ERA is the first diagnostic test that determines each woman's unique personalized embryo transfer timing, therefore synchronizing the embryo transfer with the individualized window of implantation. The ERA test evaluates the functioning of the genes that determine the receptivity of the endometrium

In the clinical setting, ERA definitely has a place in RIF where endometrial factor could be the contributory cause in less than a quarter of the patients

When is ERA test indicated?

It is indicated for patients with

• Previous implantation failures despite easy transfer of good looking and good quality embryos each time, healthy appearing endometrium and easy embryo transfer.
• Women with adenomyosis, endometriosis, and chronic endometritis can be beneficial as these conditions are associated with an altered endometrial receptivity.
• Persistent thin or thick endometrium is also an indication for carrying out ERA.

Is ERA test reproducible?

Yes, ERA test is reproducible and does not change over a long period of time (1–2 years). It need not be repeated in the event of a delay in treatment. 

What are the limitations of ERA test?

ERA test greatly increases the chances of having a successful pregnancy in couples with repeated implantation failure. The invasive nature of the test, the need for embryo vitrification and higher cost for ERA test and embryos vitrification are some of its limitations.

How is the ERA test done?The test is performed in the secretory phase of either a natural cycle or a hormone replacement (HRT) cycle. This is called mock cycle as the treatment has to mimic the same way during the treatment cycle.

If during a natural cycle, then the biopsy is done on LH surge + 7. If during an HRT cycle, then the biopsy is performed on exogenous progesterone start + 5 (120 hours post start of progesterone). Tissue sample of the uterine lining is taken through a biopsy pipille in the clinic itself without anaesthesia. It takes 5 minutes to take a biopsy and is not painful.The biopsy sample is sent to the lab and analysed (this takes approximately 2 weeks). Once the tissue has been collected, the genes within it are analysed in the genetic lab. This can then predict when the endometrium is receptive.

The results are termed either ‘receptive’ or ‘non-receptive’. If non-receptive, it further analyses the sample as pre-receptive or post-receptive.

What are the variations in the test results? 

Test results may come as receptive and non-receptive (perceptive and post receptive).

A receptive result indicates that the moment the biopsy was taken was the optimal transfer time to allow implantation.

If pre-receptive, then the patient needs more time (hours or days) of progesterone, so the progesterone is started earlier or the transfer is moved later.

If post-receptive, the WOI has already passed, so the progesterone should be started later or move the transfer earlierso as to allow doctors to transfer the embryo only at a point when the uterus is receptive to it.