ERA (Endometrial



ERA, also known as Endometrial Receptivity Analysis or Array is a genetic test which evaluates a small sample of a woman’s tissue to determine the best WOI (Window Of Implantation). ERA evaluates the status of Endometrial Receptivity and also identifies a patient’s unique WOI. In short, ERA finds the best timing for transplantation to occur in the womb from a molecular point of view which is unique to each individual. The WOI which lasts a few days long during a woman’s menstrual cycle occurs when progesterone creates a perfect state of implantation. At this stage, the endometrial cells are receptive to implant a developing embryo. The WOI generally occurs between day 19 to 23 of a woman’s menstrual cycles, but for some women, the WOI occurs later or earlier.

How is ERA done?

ERA requires a sample of the uterine lining obtained at a specific time in the cycle. The biopsy can be done via the “Natural Cycle” or  “Mock Frozen Embryo Cycle”.


Natural Cycle:


When the follicle achieves the size of > 18mm during a woman’s cycle, hCG is administered. This usually occurs during day 14. Progesterone is given after 24 hours, on day 16 for 6 consecutive days and biopsy is done on day 21.


Mock Frozen Embryo Cycle:


Also known as HRT cycle, supplemental estradiol is taken daily from the 1st day of cycle. After 2 weeks of estrogen therapy, the endometrial lining should achieve a thickness of >6.5mm. Exogenous progesterone and estradiol can then be administered for 5 full days and the biopsy is done on the 5th day of progesterone intake.

During biopsy, a tiny sample of the endometrial lining is acquired through a catheter through the woman’s cervix. This is a quick and painless procedure, however some women find this uncomfortable. The sample will be sent for NGS – Next-Generation Sequencing to analyse the 248 genes to assess the optimal time to place an embryo into the uterus to promote a successful implantation and pregnancy. The timing of the embryo transfer is adjusted accordingly to each individual to determine pre-receptive, receptive and post-receptive phases of the endometrium.


Who needs ERA?

ERA may be useful in women who experience recurrent implantation failure. The general guideline to recurrent implantation failure refers to 2 or more implantation failures during the IVF cycle with good number of eggs at retrieval, a good fertilization rate, the embryos appear to be healthy and high quality, the uterine lining looks good, the transfer goes smoothly, but the pregnancy never “sticks.”