How do you check the endometrium?

The endometrium is the inner lining of the uterus, which undergoes specific changes throughout the cycle. The quality and state of the endometrium are essential for the IVF protocol since the success of implantation partly depends on these parameters.

The primary function of the endometrium is to create favourable conditions for embryo implantation and subsequent pregnancy. And to perform this function, it must undergo specific changes throughout the cycle. This is the multifunctionality of the endometrium: on the one hand, it needs to ensure the attachment of a blastocyst, and on the other hand, the endometrium must be selective, that is, to prevent the attachment of deliberately incorrect embryos. In addition, another function of the endometrium is ejection when fertilization does not occur. And in the new menstrual cycle, the "behaviour" of the endometrium is repeated in anticipation of a new pregnancy.

Endometrial characteristics which make it receptive to implantation

For successful conception, the minimum thickness of the endometrium is 8 mm, while the optimal parameters are slightly larger – 9–11 mm. At the same time, there is no maximum “ceiling” here. It is believed that the protocol does not have too much thickness at which the transfer will fail.

The choice of a specific day for transfer is selected based on the implantation window. These are a few days in the cycle when the endometrium has the most optimal characteristics for potential implantation. In IVF cycles, this “window” most often falls on days 19–23 of the menstrual cycle.

If the endometrial parameters are insufficient for implantation, this is called endometrial hypoplasia. So, it is crucial to determine the reason and build up the endometrium to the desired parameters. Otherwise, there is no point in transferring.

Endometrial receptivity assessment

To assess the state of the endometrium, a fertility specialist needs to conduct additional studies and exclude possible diseases.

1 It is essential to exclude inflammation. For this purpose, endometrial tissue is taken for IHC  (immunohistochemical examinations). It is usually recommended in case of two failed protocols in a row.

2 A doctor may prescribe an ERA test at the next stage. This study helps to identify the implantation window in a particular woman with an accuracy of several hours.

3 With endometrial hyperplasia (more than 14 mm thick) or polyps found in the uterus, hysteroscopy is recommended to remove the polyp or take tissue for analysis.