Infertility

One out of six couples has fertility problems.

Fertility problems are common and their causes are numerous. Infertility can be of female origin (20-30%), male (20-30%), both (30%) and sometimes of unexplained causes (25%).

More than one in six couples experience fertility problems and this figure continues to rise.

Although ART procedures and the number of attempts have evolved since more than 20 years, the implantation rate remains low (22%) in both fresh and cryopreserved embryo transfers. This rate remains low and even if successful, infertility pathways can represent a significant source of stress for couples seeking pregnancy.

WIN-TEST®

DISCOVER

Some improvement paths

Some of the implantation failures are due to the difficulty in identifying the embryo(s) with a high implantation potential, and some others are due to the difficulty to find the best timing for embryo transfer into the uterus. In current practice, the selection of embryos eligible for transfer is based simply on the chronology of development and the morphological quality of the embryo: it is therefore a purely subjective and operator dependent procedure.

As for the transfer of embryos in the uterine cavity, it is carried out by default between the 2nd and 5th day after fertilization. However more than 2/3 of implantation failures are associated with a defect of endometrial receptivity. The need to identify the best timing for embryo transfer into the uterus is therefore of crucial importance in ART.

The innovative tests proposed by GAIN are the result of more than 15 years of academic research and aim at the concomitant exploration of embryonic competence and endometrial receptivity.

Our goal is to guide embryologists in the selection of embryos with high implantation potential while ensuring that the uterus is ready to receive that embryo. This personalized management increases the chances of pregnancy.

The concept of the endometrial receptivity window

During each menstrual cycle, the uterine lining called the endometrium undergoes a cyclic renewal alternating phases of regression (menstruation), proliferation and maturation. These different phases are under the influence of ovarian hormones, estrogens and progesterone.

Coordinated variations in the concentrations of these hormones allow the synchronization of ovulation, fertilization and embryo implantation. As shown in the graph, increased LH (luteinizing hormone) surge causes ovulation. Just after ovulation, oocyte fertilization by spermatozoa can take place in the fallopian tubes.

During the following days, the embryo will develop by gradually migrating from the fallopian tubes to the uterus, site of the embryonic implantation. At the same time, the endometrium matures and when the progesterone reaches its peak of concentration, it becomes receptive to the embryonic implantation.

The endometrial receptivity window describes the timing of the cycle during which the endometrium is ready to host an embryo. The synchronization between the arrival of the embryo ready to implant and the endometrium ready to receive is therefore a key step for successful implantation.

The delay of the endometrial receptivity window: one of the reasons for implantation failure

A failure to synchronize the dialogue between the embryo and the endometrium may be one of the causes of embryo implantation failure in some women. Research conducted by the scientific team of GAIN has shown that the timing and duration of the implantation window is patient-dependent (Haouzi et al., 2021). On the other hand, we showed that 80% of patients who had repeated embryonic implantation failures had a delay of the implantation window, varying from 1 to 4 days.

Assessing the endometrial receptivity profile in women who have had repeated embryonic implantation failures is therefore essential to allow these women to reach a successful pregnancy. This strategy increases the live birth rate by a four factor (Haouzi et al., 2021).

The WIN-TEST to detect the endometrial receptivity window

During the period when the endometrium is said receptive to embryonic implantation, some genes are specifically expressed by the endometrium. The analysis of these genes expression helps to distinguish a receptive endometrium from a non-receptive endometrium, and thus to determine precisely when the endometrial receptivity window is located in time.