During this event, Dr Lyubov Mykhaylyshyn, PhD, Head of the IVF Department at Fertility Clinic Alternatyva, discussed the most common uterine factors that can impact implantation failure.
During her presentation, Dr Mykhaylyshyn discussed uterine factors in recurrent implantation failure management and focused on the following issues, such as Müllerian anomaly (partial septate uterus), uterine niche, uterine fibroids as well as adenomyosis.
The topic of the partial septate uterus has long been controversial, even regarding its very definitions. For instance, under what circumstances do we classify a uterus as septate? When using the ESHRE classification, we often overdiagnose this condition. However, using the American classification, we may miss some cases. From a clinical perspective, the best definition appears to be the C criteria, which considers an internal invagination of the myometrium in the fundal area equal to or more than 1 cm as a septate uterus.
Recently, the American Society of Reproductive Medicine experts updated the criteria for diagnosing septate uterus. They also agreed that an invagination depth of more than 10 mm should be considered as a uterus with a septum. However, it must be acknowledged that, despite the diagnosis of a partial septate uterus, many women experience normal fertility and pregnancies. Only 25% of women diagnosed with a septate uterus experience repeated pregnancy loss, infertility, or implantation failure.
This raises the question: why do some patients with a septate uterus experience infertility, while others do not? Similarly, why don’t all patients with a septum have miscarriages? The answer is that not all septa are the same. There is significant clinical heterogeneity among septate uteri in terms of length, septal thickness, vascularity, and other factors. Histological studies show that uterine septa in patients with recurrent implantation failure or repeated pregnancy loss are more vascularized and contain more muscle components compared to those in patients with idiopathic infertility. Conversely, uterine septa in patients with infertility often have lower vascularization, a predominance of connective tissue, and other molecular differences.
The mechanism of implantation failure in cases of septa may be mechanical or molecular. For example, uncoordinated uterine contractions, secondary effects of endometriosis, or a decrease in certain molecules responsible for implantation could play a role.
Recent systematic reviews indicate that the presence of a septate uterus significantly reduces clinical pregnancy rates compared to women without this congenital abnormality. These reviews also concluded that removing the uterine septum significantly increases live birth rates.
For instance, a recent large study published in 2023 included over 1,000 participants with septate uteri undergoing IVF. The study concluded that the presence of a septum was associated with unexplained infertility, repeated pregnancy loss, and recurrent implantation failure.
Interestingly, the structure of the myometrium in the uterus is more complex than the myometrium in the heart. This raises the possibility of developing an electrohysterogram, analogous to the electrocardiogram used in cardiology, to better understand uterine function. In the future, this tool could help distinguish subtypes of septate uteri and identify characteristics predictive of miscarriage, impaired implantation, or other obstetrical failures.
To summarize this section:
With the increasing rate of C-sections, awareness of complications after C-sections is growing. One long-term complication is the uterine niche, caused by incomplete healing of the myometrium at the scar site.
A uterine niche is defined as a depression in the scar measuring 2 mm or more. The frequency of niches after Caesarean sections varies depending on the surgical technique. In ultrasound examinations, up to 50% of niches may not be visualized without the presence of fluid. Niches in the non-pregnant uterus may be filled with fluid or empty. They can be asymptomatic or associated with clinical manifestations like discharge, bleeding, or cramping. However, the presence of symptoms does not always correlate with the size of the niche.
To improve detection, liquid or gel sonohysterography is recommended.
A notable study published in the American Journal of Obstetrics and Gynaecology included over 500 patients who underwent embryo transfer after PGT-A. Both women with a history of vaginal delivery and those who had undergone C-sections were included. The study concluded that the frequency of euploid embryo implantation in frozen cycles was significantly higher in women with vaginal delivery compared to those with C-sections.
An important conclusion of this study was that a C-section, with or without isthmocele, significantly reduces the implantation rate after the transfer of a euploid embryo, compared to women with previous vaginal delivery.
The mechanisms of implantation failure in the uterine niche are as follows:
All of the above can negatively impact the success rate.
There are several options for treating symptomatic niches:
Another study showed that the incidence of spontaneous clinical pregnancies was significantly higher in the hysteroscopic uterine niche resection group compared to the group without resection, where the niche remained. The authors concluded that the uterine niche might be associated with significantly lower success rates following single embryo transfer.
Many studies are confirming the negative impact of fibroids on obstetric outcomes, but the effect on fertility remains less clear. However, a large meta-analysis involving more than 70,000 participants showed that fibroids were diagnosed significantly more often in patients with infertility than in those without fertility issues.
We know very well that the presence of submucosal fibroids (type 0, 1, and 2) results in a significant 70% reduction in clinical pregnancy rates. However, the important question is whether other types of uterine fibroids cause implantation failure.
There are several mechanisms explaining how myomas can negatively affect fertility:
Regarding intramural fibroids, particularly those in contact with the endometrium (type 3 fibroids), we know that fibroids can produce biologically active molecules that negatively impact implantation. The closer a myoma is to the endometrium, the more negative its effects are. Studies show that type 3 fibroids decrease implantation rates by 12%, clinical pregnancy rates by 16%, and live birth rates by 13%.
One of the studies where patients with intramural-type fibroids were divided into two groups based on the frequency of uterine contractions concluded that a decrease in pregnancy rates was observed in the high-frequency peristalsis group caused by intramural fibroids. Additional data may be needed to establish more consistent indications for intramural fibroid treatment, which may help avoid recurrent implantation failure. The uterus has its peristalsis, which can be evaluated in daily practice. In standard ultrasound mode, these waves are not visible, but by accelerating the video, we can observe and count them.
The take-home messages regarding fibroids are as follows:
Regarding adenomyosis, there is now a consensus on the definition according to ultrasound features. We have direct and indirect signs, which are extremely important from a clinical point of view. A recent study on the impact of adenomyosis on IVF outcomes found that the outcomes were strictly dependent on the localization of adenomyotic lesions.
The presence of adenomyosis in the junctional zone close to the endometrium is associated with more than a threefold increased risk of miscarriage. Diffuse adenomyosis in the junctional zone and severe adenomyosis doubles the risk of miscarriage. However, adenomyosis localized in the outer myometrium does not impact the miscarriage rate. This suggests that the endometrium, functional zone, and inner myometrium all play important roles in the implantation of the blastocyst.
Now, more evidence confirms that downregulation using GnRH agonists, birth control pills, or aromatase inhibitors reduces estradiol levels before embryo transfer. This approach is important for improving pregnancy outcomes in women with adenomyosis.
Related reading:
Firstly, we follow the recommendations of the American Society for Reproductive Medicine. Initially, non-invasive methods like ultrasound examination are used. It’s extremely important to use 3D ultrasound, as regular 2D ultrasound can miss uterine malformations such as septate uterus, bicornuate uterus, unicornuate uterus, etc.
The American Society for Reproductive Medicine also recommends sonohysterography. This differs significantly from traditional ultrasound because, during this procedure, fluid is introduced into the uterine cavity. It is particularly useful in cases where the cavity is not visible, such as when fibroids or adhesions are present. This method helps us better prepare for hysteroscopy by identifying issues such as submucous fibroids or adhesions in specific locations.
Lastly, hysteroscopy is a key method for properly diagnosing conditions like chronic endometritis. Recent consensus published by experts in this field has expanded the definition of abnormalities to include additional signs. During hysteroscopy, suspicious areas of the endometrium can be biopsied and tested for markers like CD138 plasma cells to rule out chronic endometritis.
Hysteroscopy is also less invasive now, as new cameras allow the procedure to be done without general anaesthesia. The cervical canal does not need to be widened significantly, and patients can even communicate with the doctor during the procedure.
There is an ongoing debate about whether hysteroscopy should be performed for everyone before the first IVF attempt. Some specialists support this approach, while others recommend it only after a failed IVF attempt. In my daily practice, if there are risk factors for chronic endometritis or a history of uterine issues, I recommend hysteroscopy before the first embryo transfer to avoid a negative IVF outcome.
We generally prefer to perform a 3D ultrasound in the luteal phase or at a time when the endometrium is not thick, as it allows for better visualization. However, it does not make a significant difference in many cases.
Regarding the second question, there are differences between a sonohysterography and a saline sonogram. In sonohysterography, fluid is used to examine the uterine cavity, but no balloon is inserted. With saline sonography, a balloon is used, and this can obstruct part of the uterus, sometimes missing up to 30% of the cavity, especially areas like the uterine isthmus. These differences make the two procedures distinct.
Sonohysterography is recommended by the American Society for Reproductive Medicine as a method to examine patients with infertility. However, it is still controversial whether it should be done for everyone.
No, MRI is not a diagnostic method for chronic endometritis. It may be helpful in cases of synechiae or specific structural issues, but chronic endometritis requires a hysteroscopic examination. During hysteroscopy, we visually inspect the uterine cavity and take biopsies from suspicious areas. These samples are then tested under a microscope using immunohistochemical methods to count plasma cells. These two methods—hysteroscopy and biopsy—are essential for making an accurate diagnosis.
First, I would strongly recommend preimplantation genetic testing for aneuploidy (PGT-A). Age significantly impacts success rates, even with euploid embryos. For example, a euploid embryo at 35 years old has a success rate of up to 70% per transfer, while at 45 years old, it is about 45%, which is nearly half.
Regarding dysbiosis in the endometrium, while this is an emerging area of research, evaluating the microbiome accurately is still challenging. Contamination during sampling through the cervix is a known issue. However, if there are signs of chronic endometritis, it should be treated.
That said, the primary focus should remain on the embryos. Miscarriages and implantation failures are often linked to embryonic factors. So, while addressing uterine issues is important, ensuring the highest quality embryos is critical for improving outcomes.
Asherman syndrome is a challenging condition. Preventing adhesions after treatment is critical. We use special balloons and PRP (platelet-rich plasma) treatment. PRP is highly beneficial in these cases. Depending on the severity and location of the adhesions, we may need to use surgical energy to remove them.
In my practice, I use PRP in various forms, including infusions or direct injections into the endometrium during hysteroscopy. This approach often helps.
For further preparation, I prefer natural cycles when possible. If the patient ovulates, I prescribe HCG to stimulate the corpus luteum. The corpus luteum produces vascular endothelial growth factors, which are vital for improving blood supply to the endometrium. This approach can significantly improve outcomes, especially when combined with high-quality embryos.
It depends on the type, size, and location of the fibroids. According to the FIGO classification, there are at least 8 types of fibroids.
For submucous fibroids (types 0, 1, or 2), removal is recommended, especially if they are larger than 2 cm and there has been a failed IVF attempt. These can be removed through hysteroscopy, which is less invasive than laparoscopy or open surgery.
I would not recommend removing subserosal fibroids (type 7) unless they have a peduncle, as these can twist and cause severe pain or necrosis.
Modified natural cycles are generally more effective in such cases. HCG is prescribed during the cycle to stimulate the corpus luteum to produce growth factors like relaxin and vascular endothelial growth factors, which are essential for endometrial recovery.
There are also experimental approaches, such as intrauterine devices that release growth factors. Preliminary studies from Japan suggest these devices could be beneficial, but they are not yet commercially available.
Starting with a natural cycle and incorporating HCG after day 7 can optimize outcomes for patients with Asherman syndrome.
If you have recurring Asherman syndrome, we need to see what type it is. There are different types of Asherman syndrome. We need to look at the endometrium—its thickness, its structure. Sometimes, after a hysteroscopy to remove adhesions, the endometrium looks great, and the success rate can be good. It depends on the ability of the endometrium to recover.
What was unexpected for us was Baris Ata’s study. It was discussed worldwide because it showed that even with a thin endometrium—less than 7 mm but without severe adhesions or major Asherman syndrome—if we transfer a high-quality embryo, the success rate can be similar to a patient with normal endometrium. This is especially true with egg donation programs, where embryos from younger donors can sometimes implant successfully in poor endometrial conditions.
There are risks, of course, such as placenta previa, placenta accreta, bleeding during pregnancy, premature delivery, or low birth weight. But if the embryo is strong, it can overcome many of these issues.
I’ll mention a few possibilities here.
First, we are seeing promising research from Alexandra and Ashley Moffett regarding NK cells (natural killer cells) in the uterus. Detecting NK cells is challenging, but their role in implantation is crucial. These researchers divided NK cell receptors into three categories: weak, medium, and strong. If both partners carry certain HLA gene types—like C2 genes—it may reduce NK cell activity, making implantation difficult.
In such cases, we prescribe G-CSF (granulocyte colony-stimulating factor) and HCG, which can activate NK cells. I’ve seen success with this in couples who experienced failed IVF attempts, biochemical pregnancies, or even recurrent pregnancy loss.
Second, autoimmune issues like anti-nuclear antibodies, anti-thyroid antibodies, and antiphospholipid antibodies are important to exclude. Chronic endometritis should also be ruled out.
According to ASRM guidelines for recurrent pregnancy loss, we test for protein C, protein S, and antithrombin deficiencies, as well as inherited thrombophilia. In severe cases of recurrent pregnancy loss, intravenous immunoglobulin (IVIG) may be considered.
For your specific case, with C2C2 genes and KIR AA phenotype, there’s a possibility that the baby could inherit both C2 genes from you and your husband, creating additional risks. In such situations, HCG or G-CSF may help. Dr. Scarpellini’s study from 2008 showed that a low dosage of G-CSF (100 units per kilogram) can have a positive effect.
While the situation is complex, these options could potentially improve your chances.
Based on current data, KIR C1C1 is not linked to implantation issues. Even with the KIR BB phenotype or C1C2, implantation problems are unlikely. However, obstetric complications may arise later, but implantation itself shouldn’t be affected.
Yes, firstly, in a donor cycle, it’s easier to choose a donor. What I would recommend is if you are deciding on the donor, and you have a KIR AA phenotype, I would recommend you take a donor with C1 C1 phenotype. In the case of cure AA receptor, it would be bad to take a special donor with C2 C2.
Yes, there are studies by Diana Alecsandru. I’m a big fan of her. Her studies showed that double transfer, like embryos, works worse. It’s better to transfer one embryo when we have KIR AA and C2 C2 type. But frankly speaking, from my practice, I did these double transfers because, you know, aged women don’t want to make PGT-A and have a low risk of having a chance, so we transfer two in the case of cure AA and C2 C2 type, and she was successful.
I had a good experience because we started to do cure phenotypes five years ago, and we were first in Ukraine. People even from Kyiv and other parts were sending us samples, and we tested a lot. I can’t say that it’s a very frequent case when we have these improper matches, but still, we find it in cases when people failed to have a successful attempt, especially those who had polyploid embryos and are young, etc.
I like this activation of leukocytes, and it helps. But the problem is sometimes, if you have AO antibodies, especially high antinuclear antibodies or some other antibodies, these types of medications also stimulate antibodies. In these cases, I had very challenging situations. So, also be careful, there is a proper solution for this, but you have to be very careful when adding something new, especially if you have antibodies and are going to use Granulocyte Colony Stimulating Factor (GCSF).
Adenomyosis was a very controversial diagnosis for decades. There is a very nice organization, ISUOG, International Society of Ultrasound in Obstetrics and Gynecology, and they did a big job. We have so-called MUSA criteria for adenomyosis, and recently they were updated. Now, at least we have some kind of correlation because we could not understand whether it had a negative impact or not. I showed you this in the last slides of my presentation, and I shared with you this very important study, which was published in Fertility and Sterility in the American Journal.
It is important to remember that there are three main signs of adenomyosis when we can say with certainty that it’s adenomyosis. First, there have to be little cysts, black cysts, in the myometrium. Second, there have to be white lines under the endometrium that connect with the endometrium. Third, there are islands of hyperechoic areas.
The impairment of implantation, as shown in this study, happens if these locations of adenomyosis are close to the inner part of the endometrium, or at least in the inner part of the myometrium. If this is the case, what we know from studies is that preparation for embryo transfer with downregulation would be beneficial. For decades, there were studies and even extra guidelines about endometriosis, etc., that said it doesn’t differ, but yes, it does differ.
If we use GnRH agonists or, as this study shows, just birth control pills without a break for at least a month and a half, and giving a lot of progesterone, it helps. In adenomyosis, we have a situation called progesterone resistance because adenomyosis is inflammation, and progesterone has to overcome this inflammation. It has to overcome the extra estrogens that are produced in the uterus.
So, altogether, downregulation with different medications, birth control pills, and adding additional progesterone—more progesterone than usual, either in injections or even per rectum in Europe—would have a beneficial effect in adenomyosis if it truly is present.
If it were 60 mm, yes, I would recommend an operation before the embryo transfer. But if it is a subserosal myoma of 22 millimetres, I would not believe that it is a risk. But frankly speaking, I have had a few cases where we also transferred donor embryos—like from an egg donation program—and it was just a myoma, a fibroid of about 35 mm, I suppose. It was type five, which we call “five,” partly subserosal and intramural. We had two failed attempts, and just after we removed the fibroid, we got pregnancy.
At one moment, we transferred one embryo—no result. The second time, we transferred one embryo again—no result. And finally, when we removed the fibroid, we got a result. Yes, this recurrent implantation failure is something to think about. How we calculate recurrent implantation failure is if we have the embryo after PGT (Preimplantation Genetic Testing). If we have at least a 65-70% success rate, it is high, right? So, if we transfer twice with a 70% success rate and no result, we must think a lot about what the reason is. We checked everything, even including the cure receptors, anti-lipid antibodies, and chronic endometritis results. But with 22 mm and subserosal, it’s too small. I would not believe that it’s the issue.
That’s a good question about high NK cells. There are so many factors that can influence NK cells. Honestly speaking, sometimes I also detect high NK cells in the blood. But what I pay attention to is the cytotoxicity because we know about “so-called cytotoxicity.” We have different markers for this, and there is a nice marker, p46, which makes it easy to detect. You can easily remove the blood because, in proper immunological laboratories, they don’t like to conduct cytotoxicity tests when you have transportation of blood. You just need to take the sample and immediately test it.
About extremely high NK cells, yes, I would believe it if it were extremely high, like 25-30, for example, CD56 or CD 1656. Sometimes what may be wrong is improper downregulation of NK cells. Some amount of NK cells have to be present, and if you use a lot of partners alone, it can be too much and even harm implantation.
If we do not have any implantation, and we fail again and again, and HCG remains negative every time, I do like double transfers. I don’t believe in the “window of implantation” theory. We did it so many times—we used AIR, we used PGT. I had patients like that. I’ve transferred embryos outside the “window of implantation” and they got pregnant. But what we know now is that good-quality embryos produce exosomes. Some parts of the embryo get outside, and these parts, like exosomes and micro-RNAs, help make the endometrium better.
It has to work because we know that the genes in the endometrium are very complicated. We know a lot about Fox genes, Hox genes, etc. Sometimes these genes just don’t work properly, or there aren’t enough of them. So, what I see in my practice that works: if I transfer one embryo on the fifth day of progesterone and then another one on the seventh day, something happens. All together, mostly, we have a single pregnancy, but sometimes it even results in a double pregnancy. In severe cases, I do this if I see that failure happens again and again.
After hysteroscopy, if we find something, like chronic endometritis, and we have a lot of plasma cells (more than 15-20 highly purified fields), then after antibiotic treatment, we repeat the test. Mostly, we use a pelvic test with aspiration of the endometrium to check if it’s okay. We do not usually repeat hysteroscopy, as it’s a bit expensive. However, in cases where we have adenomyosis or endometriosis and the patient has failed to achieve pregnancy, I usually recommend repeating hysteroscopy after a year. In cases of adenomyosis, we observe more frequently these types of issues like micropolyposis and chronic endometritis due to too high estrogens or after pregnancy loss or bleeding. In these cases, I would suggest repeating hysteroscopy. If hysteroscopy was mentioned in this question, yes, I believe this is the test being referred to.
I’m also careful with HCG because, sometimes, the overactivation of NK cells can be problematic. Yes, I did use HCG when I was a younger doctor, around 20 years ago, when studies showed that using HCG improved success rates. But I can’t say I prescribe HCG for everyone. Mostly, if I do prescribe it, I would recommend it on the day of the embryo transfer and again 3 days after. Not more often than once every three days, because we know that HCG mostly acts for 7 days. If I want to support the corpus luteum, I may use it once a week.
As far as I understand, you are referring to pronuclear transfer, right? When we fertilize the donor egg and then transfer our own pronucleus inside it? Frankly speaking, Ukraine was one of the first countries to do this in 2016, and the first baby was born there. A doctor from New York performed the same procedure in Mexico around the same time. But what we observe from this practice is that it works better in younger women, around 30 years old. At 46, it may not work as well.
We need to remember that making this procedure involves transferring some additional DNA from mitochondria. So, children born from this procedure could technically have DNA from three people because part of the DNA is located in the mitochondria. If we use mitochondria from the donor, the child will inherit their mitochondrial DNA, along with the parents’ DNA. The first children born using this method are probably about 17 years old now. The procedure used involved injecting cytoplasm from the donor egg, which had many mitochondria, into the patient’s own egg. A few children were born from this, and there were up to 30 children born using this method. However, we still do not know the long-term effects, especially if there will be additional diseases as these children grow older. Frankly speaking, this method is still experimental, so you need to consider that.
Frankly speaking, if there is no endometriosis or anything related to adenomyosis, I prefer natural frozen embryo transfers. They are associated with fewer obstetrical complications, especially with donor eggs, where there is a higher risk of hypertensive disorders and placental issues. Natural cycles are also associated with less bleeding, and we don’t use many medications, which is also important. If we can make a fresh cycle, a natural embryo transfer cycle is great. Regarding NK cells, if we want to suppress them further, we just use more progesterone—that’s it. Progesterone works well on NK cells. The more progesterone, the less activity of NK cells. Estrogens also have an impact on NK cells. If we take a lot of estrogens, they also affect NK cell activity. So, I would recommend a fresh, natural cycle for a frozen embryo transfer.
