During this session, Dr Laura Garcia de Miguel, Medical Director at Clinica Tambre discussed all available tests that can help identify the causes of embryo implantation failure, and possibly increase the chance of getting pregnant.
Dr Laura Garcia started her presentation by explaining the definition of embryo implantation, it is when the blastocyst (5-day embryo) joins the maternal endometrium to carry on its intrauterine development. It includes different steps, it starts with the hatching, apposition, adhesion, and invasion. The implantation success depends mainly on gametes quality, eggs, and sperm that will produce the embryo, the technique and the correct moment of the embryo transfer is also important, there must be a proper dialogue between the embryo and the endometrium. If it does not occur, that may cause possible problems in coagulation or the immunological system, which can lead to failure. If the embryo is not transferred in the correct phase of the luteal phase of the endometrium, it’s not going to implant.
There are different definitions for implantation failure, one of those from the Spanish Fertility Society defines implantation failure as a failure to achieve a pregnancy in women younger than 40 years old after having transferred at least 4 good quality embryos (in cell stage) in both fresh and frozen embryo transfer.
What is not an implantation failure? Women older than 40 years old go through IVF because one of the main reasons these women are not getting pregnant is chromosomal abnormalities. Low ovarian response or low ovarian reserve leads to a poor number of eggs retrieved, and there will be a low probability of selecting good embryos. Other factors that are not the reason for implantation failure are some medical conditions such as endometriosis or hydrosalpinx, low-quality embryo transfer, and uterine cavity alterations such as polyps, and fibroids. Also, an inappropriate endometrium development, such as refractory endometrium, where the endometrium is very thin.
One of the causes of implantation failure could be clotting alterations in our haematological system. There could be some hereditary thrombophilia such as Factor V Leiden and factor II Prothrombin mutation, MTHFR mutation, which is evolving in the folic acid metabolism, Factor XII mutation and many others. There could also be protein C and S deficiency or Antithrombin III deficiency, which makes you more likely to get abnormal blood clots. In this kind of situation, the use of aspirin and, or heparin will be necessary. Other problems include antiphospholipid syndrome, where women are creating antibodies in their blood, such as Anti-cardiolipin, and anti-beta2 glycoprotein I antibodies, which could also affect embryo implantation.
For instance, there are many patients undergoing reproductive treatments that have anti-thyroid antibodies, which is necessary to treat with Prednisone. However, if there are high levels of anti-thyroid antibodies, levothyroxine is also used to try to have a good TSH level, and yet the embryo is still not implanting, Prednisone is strongly recommended.
Another issue is an antiphospholipid syndrome, which involves Anti-nuclear antibodies (ANA), Anti-cardiolipin antibodies (ACA), and Lupus anticoagulant, it could also be associated with previous failures or miscarriages as well as thrombosis. The treatment with aspirin and heparin is offered.
A lot of controversies are still related to the natural killer cells, but if 3 blastocysts with good morphology have been transferred to a good endometrium and it still fails, it’s better to check the NK cells, which can be done in the blood or the endometrium, that depends on each clinic. If there is an expansion of the natural killer cells, which normally prevent the organism from viruses and other infections, but in the context of the reproductive outcome, it could lead to failures. In such situations, an immunological consultation is required, the immunologist will either recommend corticoids such as Prednisone, intralipid infusions or immunoglobulin infusions to try to reduce the NK cells expansion.
Apart from higher NK cells level, some women have an expression in the receptor of their lymphocytes called KIR AA. This is linked to miscarriages, complications during pregnancy and also implantation failures. Therefore, in the event of not being able to find any other reason for the failure, in the case of egg donation, it’s best to select a donor having C1C1, which is the best combination for KIR AA. However, in the case of IVF with own eggs and one partner’s sperm, where it’s impossible to change the combination, immune medication is offered to make that response between KIR and HLA less aggressive and increase the probability of the pregnancy continue developing.
Some patients need to remove gluten from their diet because the reason for their previous failure is unknown. Such patients can have some genetic issues, and a higher risk of celiac disease, or they can be diagnosed with celiac disease. In such cases, a gluten-free diet is recommended at least 1 month before transfer and throughout pregnancy.
It’s very important to classify the embryo as good, intermediate or bad quality, depending on the cell number, the percentage of fragmentation in their cells, the nucleation, alterations in pronucleus or vacuoles and also the cell-division moment.
Not only the external quality of the embryo is important, but its genetics, at a more advanced age, the risk of aneuploidies is much higher. That’s why in women at 38-40 with previous failures, it’s recommended to perform PGT-A testing to check the embryos and whether they are abnormal or not.
It is always recommended to do a basic semen analysis and check concentration, volume, motility, but also DNA fragmentation, it should be thoroughly checked if it is a single or double fragmentation which is high and what can be done for the such patient in terms of pre-treatment and technique in the lab to maximize the outcome. In very specific cases, FISH or Chromosperm is recommended to see if there is a genetic problem. Even in normal sperm parameters, single-strand or double-strand DNA breaks inside sperm cells can be identified, therefore, the CometFertility test is recommended.
If there is a high rate of single-stranded DNA fragmentation, there will be a lower fertilization rate. If the issue is in the double-stranded DNA fragmentation, there is a higher chromosomal alterations risk in the embryo. Both will lead to lower implantation.
Genetic testing such as Chromosperm or FISH (Fluorescence In Situ Hybridization) is used to check if the possible issue of the failure is a genetic abnormality in the embryos and if the reason for that is the sperm. In such a situation, sperm donation might be the best solution.
For patients with multiple rounds of IVF, and multiple failed implantations, it’s always recommended to check the uterine cavity. It’s best to check with the 3D scan if there are any problems the 2D scan failed to show, such as very tiny polyps or fibroids in the cavity (submucosal fibroids). There could also be some other issues that could only be seen with hysteroscopy, such as Asherman’s syndrome.
Other things that need to be excluded are hydrosalpinx. In the case of hydrosalpinx, salpingectomy is required before any transfers.
Another situation is uterine malformations, which can be checked with a 3D scan or MRI. There could be a T-shaped uterus or a septum which needs to be evaluated by a surgeon on how to proceed to improve the cavity.
If the lining doesn’t have a good thickness, which is at least 6.5 millimetres (the ideal is to have more than 7 millimetres) before the transfer, it’s best to postpone the transfer for the next month. The endometrium can be prepared with the use of Aspirin, Viagra, or vitamin E or any other medication that could increase the size of the lining.
In the event of implantation failures, it’s always necessary to study endometrial receptivity. Tests, such as ERA, and TIME can help with that.
The window of implantation is known as the period when the endometrium has the best conditions for embryo implantation. The endometrium receptivity during this period is short and depends on the effect of estrogens and progesterone in the uterine lining. It varies between women. It is reported that 30% of women have an abnormal window of implantation, so it should be investigated before further transfers. 30% of patients will have abnormalities in this test and will have different gene expressions, so the embryo transfer needs to be personalized.
For microbiome infections, EMMA, ALICE, or META are used where the endometrium is biopsied. It will show if there are any infections or microbiome abnormalities. A pre-treatment with antibiotics, etc., is performed a month before another transfer to restore a beneficial microbiota.
Preimplantation Genetic Testing (PGT) allows the selection of chromosomally healthy embryos, and it increases the chance of having a healthy baby by reducing the risk of miscarriage, there is an increased probability of pregnancy per transfer because a single transfer is recommended in such cases. It also reduces the duration of treatment and the number of cycles needed. The indications for genetic testing are advanced maternal age, karyotype alterations and patients affected by monogenic genetic diseases.