ERA тест ендометриална рецептивност

The Endometrium and Endometrial Receptivity

Endometrium or uterine lining complaints are a leading cause of female infertility. Endometrial receptivity is among the most important factors in embryo implantation into the endometrium. The endometrium is receptive when it is ready to accept embryo implantation: something that usually happens between the 19th and 21st day of the menstrual cycle (five or seven days after ovulation). This period of receptiveness is termed the implantation window.

What is ERA® (Endometrial Receptivity Array)?

This is a new diagnostic method for ascertaining the uterine implantation window: the moment when the uterine lining is ready to accept the embryo. The method measures the gene expression profile of endometrial tissue.

How is ERA® Conducted?

A biopsy of the uterine lining is performed to obtain a sample for analysis. The easy and rapid procedure is conducted by a gynaecologist in outpatient conditions.

The tissue sample is subjected to highly specialised genetic analysis. Special software analyses information and classifies the endometrium as receptive or non-receptive. The analysis helps determine whether the theoretically predicted uterine implantation window coincides with the actual implantation window or is displaced.

Non-receptivity indicates that the implantation window is displaced. In such cases, based on the prior result, a new period is set for a further biopsy. Once implantation window displacement is ascertained, a successful embryo implantation may be planned for a future cycle.

What are the Benefits of ERA®?

It is known that some 28,6 per cent of women with reproductive complaints have actual implantation windows that do not coincide with theoretical ones. In one per cent of cases, there is no implantation window at all. Prior to commencing in vitro procedures, therefore, it is desirable to apply the ERA diagnostic method and thus determine whether the patient has an implantation window and on which days of her menstrual cycle it occurs. This would lead to corrective measures which would raise the chances of successful assisted reproduction treatment.

Absolute Indications for ERA®:

  • Women up to the age of 37 who have undergone at least three unsuccessful embryo transfers of embryos with good morphological characteristics;
  • Women over the age of 37 who have undergone at least two unsuccessful embryo transfers of embryos with good morphological characteristics.


Relative Indications for ERA®:

  • Frozen embryo transfers;
  • Hydrosalpinx or fluid blocking of the fallopian tubes;
  • Endometriosis linked with infertility;
  • Inborn anomalies (uterus didelphys);
  • Prior to commencing in vitro procedures.


ERA® Application in Bulgaria:

ERA® innovative methods were first applied in Bulgaria at the Sofia Hospital of Obstetrics, Gynaecology and Reproductive Medicine.