The endometrium: Does it influence my fertility?

Described as the tissue or mucous layer that lines the inside of the uterus, the endometrium plays a pivotal role in a woman’s pregnancy. The endometrium will gradually change its thickness throughout the menstrual cycle in preparation for embryo implantation leading to the beginning of gestation. These variations of the endometrium are due to the action of sex hormones: estrogen and progesterone.

If fertilization of the egg or implantation of the embryo does not occur, the endometrium sheds and what we know as menstruation begins. At that moment a new menstrual cycle begins.

What is Endometrial Receptivity of the Endometrium?

Endometrial receptivity is the optimal period of time that the endometrium has to receive the embryo. Once implantation occurs and the embryo nests in the uterine wall, this attachment leads to the development of the placenta, the creation of the gestational sac and, finally, the development of a viable pregnancy.

To achieve success in treatment we need to select the embryos with the greatest implantation potential, those that are chromosomally normal and morphologically of good quality. However, some studies have proven it is just as important to maintain an endometrial environment that facilitates dialogue between maternal endometrium and embryo.

In order for the embryo to implant in the maternal uterus, the endometrium must be receptive. This happens only during a few days of the menstrual cycle, that ideal moment in which fertility clinics plan the embryo transfer is called the window of implantation.

What does it mean to have a displaced implantation window?

The window of implantation is a period of time in which the endometrium is prepared to receive the embryo with a higher probability of success. Of course, this will be unique to each patient.

We know that the endometrium is only receptive during a short period of time, from 12 to 48 hours, between days 19 to 21 of the menstrual cycle in women with a regular menstrual cycle. However, there are women who present a different endometrial receptivity: displaced window of implantation. This can be pre-receptive or post-receptive.

“According to our studies, there is a high percentage of patients with endometrial receptivity problems. We are talking 1 in 3 patients with implantation failures present a displaced window of implantation”, says Dr. Katharina Spies, Vida Fertility Institute Madrid Medical Director.

How do I know if I have a displaced implantation window?

Each patient has a different implantation window. Thanks to personalized diagnosis we can approach the study of the endometrium from a unique perspective.

The Endometrial Receptivity Test allows us to determine the exact moment to perform the embryo transfer on each patient.

The Endometrial Receptivity Test is recommended for In Vitro Fertilization treatments with one’s own eggs, EggDonation or IVF with anonymous donor eggs, Embryo donation and treatment for female couples known as ROPA Method (reception of oocytes from the partner). In all of them we need to find out the moment of maximum receptivity to increase the chances of achieving gestation.

Who is the Endometrial Receptivity Test indicated for?

Patients with implantation failure: it can be a single failure of EggDonation with good quality oocytes and semen or two failures in case of IVF with one’s own eggs of good quality.
Repeated miscarriages.
Infertility of unknown cause.
Patients with atrophic endometrium: they are patients that present changes in their implantation window more frequently. The atrophic endometrium becomes thinner and more fragile.
A BMI>30. They also tend to have a displaced implantation window.

The endometrial microbiome influences fertility

We know that in order for implantation to occur, the quality of the embryo and the endometrial environment must go in parallel. We also know that the endometrial microbiome has an influence when it comes to that efficient communication between embryo and endometrium taking place.

In the past, the endometrium was thought to be sterile, far from the current approach that considers patients as ecosystems. And according to more current studies, it has been discovered that the vaginal microbiome may be different from the endometrial microbiome. Which means that with one vaginal culture would not be enough to detect the pathogens causing infertility that are present in the endometrium.

Studies have shown that the percentage of miscarriages decreases in cases where there is a greater presence of Lactobacillus colonies (beneficial bacteria) than Gardnerella or Streptococcus (infection-causing bacteria).

What is endometritis?

Endometritis is an acute or persistent inflammation of the endometrium due to the presence of bacteria such as: chlamydia, gonorrhea, tuberculosis, or even a combination of normal vaginal bacteria.

Endometritis, besides appearing due to sexually transmitted diseases (STD), can also occur after a spontaneous miscarriage, childbirth, cesarean section, hysteroscopy or due to the placement of an IUD (intrauterine device to prevent pregnancy).

It becomes chronic when the inflammation becomes persistent, and usually in these cases the infection is asymptomatic.

Up to 30% of infertile patients suffer from chronic endometritis. This percentage can be as high as 66% in the case of women who have recurrent implantation failures.

At Vida Fertility Institute we are able to effectively analyze the endometrial microbiome using different types of tests: EMMA and ALICE. Thanks to these tests we will know if there is any imbalance in the bacterial flora of the endometrium.

The ALICE (Analysis of Infection Chronic Endometritis) test focuses on analyzing the eight pathogenic bacteria that can most frequently cause chronic endometritis.

While EMMA (Endometrial Microbiome Metagenomic Analysis) provides a broad analysis of the endometrial microbiome to improve the woman’s reproductive prognosis (the ALICE test is included in EMMA). This analysis offers a global vision of the bacterial profile that will help us to determine the type of microbiome in the endometrium: normal with a high percentage of lactobacilli or abnormal with the presence of dysbiotic or pathogenic bacteria.

When patients present an abnormal result, our specialists prescribe a personalized treatment to restablish the balance of the endometrial flora. In a fertility treatment the balance of the endometrium multiplies the chances of implantation.

Your first visit is free!

If you have any more questions or want to speak directly to a fertility specialist: your first visit if free of charge. No obligation, contact us and we will be happy to go through with you.