The formation of a pregnancy begins as a result of the interaction between the embryo and the uterus. The uterus accepts the embryo in a suitable condition. So is the uterus ready to hold the embryo at any stage?In both natural pregnancies and in vitro fertilization pregnancies, the uterus has a retention window. This ‘window’ …
The formation of a pregnancy begins as a result of the interaction between the embryo and the uterus. The uterus accepts the embryo in a suitable condition. So is the uterus ready to hold the embryo at any stage?
In both natural pregnancies and in vitro fertilization pregnancies, the uterus has a retention window. This ‘window’ remains open for a certain period of time, and the uterus is not suitable for embryo attachment before or after this period. This situation has been known for a long time and has guided the practices of us IVF doctors. Another piece of information we had was that progesterone hormone levels rising early during treatment negatively affected attachment. However, we could also experience problems in the treatment plans created with this information.
A few years ago, tests that show the timing of the uterus accepting the embryo came into use. ERA (Endometrial Receptivity Array) is one of them. As a doctor who has been involved in IVF for a lifetime, I was both very happy and initially skeptical. The claim of the test was that if good quality embryos have been transferred several times but no pregnancy has occurred, in approximately 25% of this selected group of women the day of retention of the uterus is different from the standard known. And if you follow the test’s guidance when making a transfer plan, your pregnancy rates will increase.
How is the ERA test performed?
The test is performed as follows: just like preparing for the transfer of frozen embryos, we start preparing the uterus by using estrogen hormone-containing medications starting from the 2nd-3rd day of the menstrual period. We check the uterine thickness and hormone levels after 12-14 days. If the values are appropriate, we start using progesterone-containing medications, which are the hormones that prepare the uterus for pregnancy, and we record the date and time of first use. 5 days later, we enter the uterus with a small catheter and take a sample of the endometrium tissue prepared for pregnancy. We also record the time we took it. The tissues taken are delivered to the laboratory in a special tube, and over 200 genes are examined in the tissue to inform us whether the uterus is retentive at that time.
The basic criterion here is the time between the start of progesterone and the time the biopsy is taken. For example, if this period is 120 hours, the test result comes to us as follows: The uterus is retentive during the time you take the biopsy (for example, 120 hours). Or, during this time period, the uterus’s retention period is 12 or 24 hours behind/ahead. Prepare your transfer accordingly or take a new biopsy.
Taking a new biopsy can be both very tiring and very costly, so I should point out that planning the transfer based on the information obtained from a single biopsy is also a logical and good-results option.
It is easier to explain with examples. We have a frozen fifth-day embryo and we performed ERA. Let’s assume that we took a biopsy 125 hours after we started using progesterone. If the test result shows that retention is 24 hours behind, after a similar preparation period, if everything is suitable, we transfer our 5th-day embryo after 125-24=101 hours of progesterone use. By the same logic, if the test result comes in this way, it is necessary to transfer the 3rd-day embryos after a 2-day uterine preparation. Making a transfer by making corrections-adjustments according to the ERA result is also called ‘personalized embryo transfer’.
Can the ERA test be applied to everyone?
We cannot apply the ERA test to couples who are planning to transfer fresh embryos. The embryos must be frozen. It can take up to a month for the test result to come. We can start transfer preparations in the first menstrual period after the result is available.
We have used this method in a wide range of patients for years and have gained considerable experience. According to the results we obtained, in approximately one fourth of the group of women who had previously transferred good embryos but did not become pregnant, the retention day was different – as initially claimed. And we were successful in many of our patients who had tried IVF many times by simply changing the transfer day.
As with many methods, ERA is not suitable for every couple. It is not a test that should be done in the early stages of IVF treatments. However, we know that it can change many things for some couples.
