The endometrial receptivity assay (ERA) is a relatively new diagnostic tool available to the fertility specialist. An endometrium is receptive when it is ready for embryo implantation. This occurs around days 19-21 in each menstrual cycle of a fertile woman. This period of receptivity is called the window of implantation (WOI). The lack of synchronization between the embryo and the endometrium is one of the causes of recurring implantation failure.
The endometrial receptivity array (ERA) test requires an endometrial biopsy that should be carried out 7 days after the LH surge or after 5 full days of progesterone exposure as part of a HRT (hormone replacement therapy) cycle. This biopsy can be done by the physician in the office or it can be done in the operating room as part of a hysteroscopy surgery. The ERA test analyses the expression levels of 248 genes linked to the status of endometrial receptivity, using RNA sequencing taken from the endometrial tissue. It helps to identify the window of implantation (WOI) and more exactly pinpoint the best time for embryo transfer thereby increasing the chances of a successful outcome.
The ERA test has been proven to be highly sensitive and accurate in detecting gene expression profiles associated with endometrial receptivity. It has been shown to be superior to endometrial histology (what the tissue looks like to the pathologist under the microscope). When the test is done via hysteroscopy, the physician also gains insight into the curvature of the cervical canal which can make the embryo transfer (ET) process more smooth.