During this event, Vladimiro Silva, Scientific and Executive Director at Ferticentro shared the secrets behind recurrent implantation failure (RIF) and explored the crucial role the endometrium plays in fertility challenges.
Regarding the definition of Repeated Implantation Failure, there’s not much consensus in the scientific community about what should be considered as recurrent implantation failure. Normally, it is referred to as the failure to achieve a pregnancy after at least 3 embryo transfers with good quality embryos or maybe after the transfer of 3 or 4 good quality blastocysts. What does this mean? For example, if you are trying with your own eggs, and you’re getting great blastocysts, you transfer 3 or 4 of them, and you still don’t get a pregnancy, you can consider this as recurrent implantation failure. If you are 43 or 44 years old and your eggs are not that good, then not having a pregnancy after 3 or 4 blastocysts is unfortunately more likely to happen than the opposite. You can even be 48 or 49, and you’re trying with egg donation with 3 brilliant embryos, and you don’t get a pregnancy, then you can talk about recurring implantation failure.
Some people argue that this is really just bad luck. We know that humans are not a very fertile species. A man and a woman at the age of 25, if they try to get pregnant naturally, if they are in perfect health without any reproductive issues or any other concerns, just have a 25 to 30% pregnancy rate in the natural way every month. In IVF, for example, when egg donation is performed, we are just very above that. It’s possible to get to a 60% pregnancy rate or 70% pregnancy rate with egg donation. However, statistics are what they are, and they can deceive us. If there is a 60% pregnancy rate, which is kind of the standard for egg donation, this means that if an embryo is transferred to 100 patients, 60 of them will become pregnant. We go to the remaining 40 and transfer another embryo, so 24 will get pregnant, and 16 will not be pregnant. If we go to the 16 and transfer a third embryo, 9 will be pregnant, and 7 will not be pregnant. After these 3 embryos, there is a 93% accumulated pregnancy rate, but in reality, it was always 60%.
Statistics depend a lot on the way that we look at them. We can’t make overall assumptions. We need to make sure that there are no confounding factors, meaning if the embryos are really good, if the endometrium, which is the tissue inside the uterus, is also good, then we might need to take a deeper look into it. If those conditions are not assured, maybe we’re just on the wrong side of statistics.
Keep in mind that it’s always 60%. The reality is that IVF treatments fail, and many times we don’t know why. There was a study published a few years ago in Human Reproduction Update, which is one of the main scientific journals in the IVF world. This is the official journal of the European Society for Human Reproduction and Embryology (ESHRE). These researchers have concluded that when patients are not getting pregnant, they often come to the clinic and say, “Why did it happen? Why is it not working for me?” And so, was it the egg, the sperm? According to this study, in 70 to 80% of the cases, it was the egg, in 10 to 15% of the cases, it was the sperm, and in 10 to 15% of the cases, the causes rely on the endometrium. This 10 to 15% are the endometrial causes for implantation failure, knowing that 85 to 90% of the problem is not the endometrium, it’s the embryo.
The sperm can also play a role even before the formation of the embryo, but also afterward because in some situations of sperm issues, the risk of miscarriage is increased. The endometrium is this tissue that coats the inside of the uterus, but this is only responsible for 10 to 15% of implantation failure situations, according to these statistics. There’s no consensus about this. When the issue is with the embryos, we’re talking essentially about chromosomal abnormalities. When the concern relies on the uterus, we can have an issue in the endometrium. There can be an issue with the window of implantation, the endometrial receptivity issues, but also anatomical abnormalities, immune factors, and things that are not directly related to the endometrium but rather to the uterus like some malformations and so on. It’s important to mention that typically the concern is on the endometrium side after we exclude the problems with the embryos because 85 to 90% of the time, this is where the problems are. The main way to exclude issues with the embryos is by genetically analyzing the embryos with Pre-implantation genetic testing for aneuploidies (PGT-A). What are aneuploidies? These are numerical chromosomal abnormalities. This means that your embryo has the wrong number of chromosomes. Either it has 1 chromosome extra, a chromosome missing, or other factors.
These situations are typically age-related. It means that with the progression of female age, on a very significant minor degree with male age, but essentially with female age, this type of chromosomal abnormalities increases. That causes the embryos to carry anomalies that are not compatible either with implantation or with having a healthy baby. Statistics shown on the slide were taken from Igenomix, which is one of the main labs in the reproductive genetic labs, we can see that in all age ranges, and all age classes, the probability of pregnancy with PGT-A, is pretty much the same. There is a slight difference, however, if we look at the non-selected population, pregnancy rates go down with the progression of age. Why does this happen? Because it is the transfer of embryos that have a normal number of chromosomes.
It’s important to mention that PGT-A doesn’t improve the quality of the embryo. If an embryo is not good, it will not change the embryo. It just helps to understand what’s the status of this embryo and that helps to make decisions. This is kind of the first step to study the endometrium and to understand whether the embryo is viable. Even for the best possible cases where the patient is below 35 years of age where we are transferring an embryo with the correct number of chromosomes, pregnancy rates are never above 60%. This means that in the remaining 40%, we have the other causes of implantation failure. This is where the endometrium lies.
On the other hand, if we look at another graph presented, we can see that the probability of miscarriage increases a lot when we are transferring to an unselected population. While in a selected population where we’re just transferring normal embryos, pregnancy rates, and miscarriage rates are pretty much the same. There’s a slight increase associated with age, and those are again probably endometrial factors, but it’s relatively steady on the gray bars with age when we transfer good-looking embryos.
When discussing the quality of the endometrium and its relationship with repeated implantation failure, we need to first rule out whether the issue lies with the embryo. This is because the chances of the problem being in the endometrium are relatively low, at around 10 to 15%. In cases where we have transferred good quality embryos, such as nice blastocysts or PGT-A tested embryos, and we still haven’t achieved pregnancy after three attempts or after transferring four good quality embryos, the Endometrial Receptivity Test, also known as the ERA test, is one of the first tests that has been widely used around the world in recent years.
Addressing the endometrial receptivity consists of three parts. One of them is the window of implantation, another one is the microbiome, and the third is assessing whether there are any signs of chronic infections in the uterus, called chronic endometritis. Regarding the window of implantation, we use a test called the Endometrial Receptivity Array (ERA) test, other brands are doing the same. What is this? Another graphic from Igenomix shows that in a normal cycle, there is ovulation around day 14, and then, between day 19 and day 21 is when the endometrium is ready to receive an embryo and implant. This is what is called the window of implantation, where the endometrium is ready to receive a blastocyst, which is a day-five embryo. Before this, the endometrium is pre-receptive, and after this, the endometrium is post-receptive. Why is that? The endometrium being receptive means that the endometrium starts to be under the action of a hormone called progesterone. It starts to be more vascularized and ready to receive an implant and nourish an embryo. The window of implantation sometimes is not the same for all women, and 30% of the patients have a displaced window of implantation according to studies.
So what happens? Another graphic from Igenomix shows that when you transfer an embryo, a day-five blastocyst, it needs to be within the window of implantation. This window of implantation can be corrected if, for example, the endometrium is only receptive later or earlier, and so we need to adapt to the moment when we will transfer the embryo. Why? Because we know that the endometrium needs to be ready to receive the embryo. If it is a blastocyst, it should be at five days of progesterone because that’s when the endometrium is ready to receive a day-five blastocyst. However, we know that in some cases, the endometrium, after seven days, is only ready to receive an embryo after 6, 7, or 8 days of progesterone. On the opposite, after 3 or 4 days, it is already ready with day 3 embryos. When we are outside the window of implantation, the chances of having a pregnancy are lower, the risks of miscarriage are higher, and there is a risk of wasting precious viable embryos for transferring them at the bad moment. How can we correct this? It’s relatively easy. We do a cycle preparation, like if we were doing a frozen embryo transfer, except that on the day of the embryo transfer, instead of doing the embryo transfer, we take a little piece of the endometrium, and that goes to be analyzed on a genetic slot. They run a panel for 248 genes, and the result will show whether the endometrium is receptive or pre-receptive. Since the biopsy was done at 120 hours of progesterone, we know that at that very moment, the endometrium is ready to receive an embryo or not. It’s crucial to find what is the moment to do the embryo transfer, and it doesn’t require special medication. Performing this test on those patients who had failed transfers produced better results, transferring on the day that is supposed to be done 54% of pregnancy using this information. They moved to 70, they gained 18% of pregnancy, and the cumulative rate went from 70 to 95%. The time for pregnancy was also reduced because 71% of all women gave birth within one year. These are the results of a study made in certain very specific conditions, but it’s important to keep in mind that studies done on a larger scale where they were doing this test to all patients regardless of their conditions, the test proved to be useless. Therefore, doing the test for everybody is not recommended. However, for patients that have a documented repeated implantation failure case, there is some benefit in doing this test.
Another test that can help is the test to check the microbiome and chronic endometritis. What is this all about? Until a few years ago, medical doctors believed that the uterus was sterile, it was proved that in fact, there are bacteria inside the womb. The microbiome refers to the kind of environment of bacteria that exists inside the womb. We now know that this needs to be at least 80% Lactobacillus. It means that we need to have the right bacteria inside the uterus to prevent the wrong bacteria, the pathogenic bacteria, from implanting and creating an infection because we know that a balanced microbiome with at least 80% Lactobacillus will improve your reproductive prognosis resulting in an increased chance of pregnancy and life births.
Many studies that have been done in recent years show that 30% of all infertile women have pathogenic bacteria in their uterus. Numerous studies show that having pathogenic bacteria and others is very linked to embryo implantation failure. So what we do is this. How is it done? Another preparation cycle is performed, but on the day when we should be doing the embryo transfer, instead of doing the embryo transfer, we will just do an endometrium biopsy. A little piece of the endometrium is taken and sent to be analyzed on a genetic slot. We can use that piece to check for the 248 genes related to the window of implantation mentioned, and we can also check to see what bacteria are in there. We use the test to have a view of the endometrial microbiome composition to see if there is the right percentage of Lactobacillus. Another test is called ALICE is used to see if there are bacteria associated with chronic endometritis.
From those results, we get a recommendation on what is the antibiotic that we should be using. The next real case presented a real patient case where the result was a mild dysbiosis profile. Lactobacillus were just 59 instead of 80%, but there were no pathogenic bacteria involved, so they didn’t find out any of this. Probiotics were prescribed to the patient. Sometimes, after the probiotics, another biopsy is done to confirm if it is back to normal, sometimes not. In this particular case, it was a mild change, so there was no need for that. However, as Vladimiro confirmed there were cases where the percentage of Lactobacillus was 0%. In those cases, antibiotics are prescribed just to kill potentially harmful bacteria, and then the probiotics are added to populate the uterus with the right bacteria, then it has to be checked again to make sure that everything is fine, and then we move on with the embryo transfer. There is not a universal solution for every patient.
Another thing that needs to be checked while evaluating the uterus is anatomic abnormalities. There is an exam called hysteroscopy where we go with a video camera to see the inside of the womb. This is used to check for polyps, to check for endometritis, myomas also known as fibroids, adenomyosis, malformations, etc. Some of these can be surgically corrected, some don’t, and that is treated with antibiotics. One of the studies showed that congenital uterine abnormalities can lower the reproductive outcome. However, there is no consensus about it. In the review from the Cochrane Library, it is explained that in women who have septum, there is no evidence to support the surgical procedure in these women. They say that it’s preferable not to remove the septum because it’s surgery, it’s aggressive, it can do worse than not to remove it. If a patient has repeated miscarriage or repeated implantation failure, we can look at it in another way. As a first approach, surgeries are not always recommended.
As mentioned before, problems with the uterus represent 10 to 15% of all cases. That 10 to 15%, specifically is focused on the smaller pieces within that percentage. This is probably the smallest of all these pieces: the immune and dermatological tests. There are numerous tests available in the market. For example, in France, there is a test where they assess the immune environment at the uterine level. Many other tests focus on various aspects such as NK cells, autoimmune diseases, and thrombophilia screening. However, most of these tests lack substantial proof of their efficacy. To establish their benefits, large-scale studies would be necessary. Yet, conducting such studies is extremely challenging due to financial constraints and the difficulty in finding a homogeneous sample of patients. In the realm of IVF, each patient is unique, with various contributing factors, making it hard to find a sample where the only differing factor is the presence or absence of a particular condition such as autoimmune diseases or specific genetic markers like KIR or HLA.
Therefore, the efficacy of these tests remains largely unproven. Nevertheless, we still conduct these tests as part of the protocol. From our experience at Ferticentro, one test we rely on more is the KIR-HLA test, which was found to be beneficial in numerous cases. Correcting for these factors has led to successful pregnancies and the birth of healthy children. However, it’s important to note that this process can be lengthy, especially when working with donors. In such cases, specialized protocols are crucial. There’s no one-size-fits-all approach in such cases; hence, individual assessment is crucial. Ultimately, the main goal is to achieve successful implantation in the uterus and a healthy baby.
Case 1 – a 42-year-old woman, with 5 years of infertility and 2 previous miscarriages, multiple fibroids surgical removed before seeking treatment at Ferticentro
Due to her low ovarian reserve, 2 stimulation cycles were conducted, the first to freeze her eggs and the second to retrieve more eggs for IVF. Despite these efforts, the embryo resulting from the IVF cycle was found to be aneuploid, rendering it nonviable. Subsequently, egg donation treatment was recommended, resulting in 6 blastocysts, 5 of which were euploid. After additional tests and adjustments to her protocol, she successfully gave birth to a healthy baby boy.
Case 2 – a 30-year-old woman, had experienced 2 miscarriages and was diagnosed with polycystic ovarian syndrome (PCOS)
Despite her previous miscarriages, she opted against preimplantation genetic testing of embryos. After successful ovarian stimulation, 6 blastocysts were obtained, all of which were frozen. However, the first embryo transfer resulted in another miscarriage, leading to exploring lifestyle modifications, including weight management. Additionally, probiotics were implemented, antibiotics, and a personalized progesterone protocol was introduced. These interventions ultimately resulted in the birth of a healthy baby.
Case 3 – a 44-year-old woman with a diminished ovarian reserve, who underwent an egg donation cycle.
Despite transferring 4 blastocysts across 2 cycles, both attempts were unsuccessful. Further investigations revealed issues with endometrial receptivity and microbial imbalance. Additionally, it was found that she was found to be a carrier of an autoimmune disease and had thrombophilia. Collaborating with specialists, her treatment was tailored accordingly, which ultimately led to a successful pregnancy and birth.
These cases highlight the complexity of fertility treatments and the importance of personalized care. The correct approach underscores the significance of thorough evaluation and tailored interventions. Every case is unique, and the most important thing is to provide individualized care to each patient.- Questions and Answers