Implantation failure is a sad but quite common fact in the assisted reproduction reality. However sad and unfair it may seem, it is important to know its background and the most common reasons. In this webinar, dr. Esther Marbán Bermejo, Gynecologist & Specialist in fertility at Clinica Tambre
, is talking about the causes of failure of an embryo to implant in the IVF cycle.
Understanding embryo implantation
To know the reasons for embryo implantation failure, it is important to understand embryo implantation itself. Dr. Esther Marbán Bermejo explains it as a procedure by which an embryo (mostly at the blastocyst stage) joins the maternal endometrium to carry on its intrauterine development. There are different stages the embryo has to follow to implant: hatching (when the embryo starts to get out from its external membrane – zona pellucida), apposition (when the embryo approaches the endometrium so that the internal cell mass points towards it), adhesion (when the embryo joins the endometrium) and invasion (when the embryo starts to go inside the endometrium to implant). All the stages have to be followed properly in order for the embryo to implant successfully.
The embryo implantation success generally depends on a few factors and these are gametes quality (eggs and sperm), embryo quality, a technique and a proper moment to do the embryo transfer, a proper dialogue between the embryo and the endometrium and – last but not least – suitable luteal phase support.
Decreasing the embryo implantation chances
The implantation failure is defined 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. Dr. Esther Marbán Bermejo admits that the latter is a classical definition but in the current clinical practice, doctors do not wait to transfer 4 embryos. Nowadays embryos are generally transferred at the blastocyst stage in order to increase implantation and pregnancy rates. Doctors do at least 2 good quality blastocyst transfers and then – when a patient fails to get pregnant – they start to think about implantation failure.
According to dr. Marbán Bermejo, there are many factors that can affect the implantation – but they are not always the cause itself. First of all, women over 40 years old have a decreased implantation rate. The reason is the quality of the embryos: if the embryo is not chromosomally healthy, it has a lower chance of implanting. That’s why – in order to increase the chances of implantation – it is very important for the embryos of over 40-year-old women to undergo pre-implantation genetic screening (PGS). Secondly, if a woman is older than 40 years old and has a low ovarian reserve, the number of embryos available to transfer and freeze will be significantly decreased. As a result, the chances of implantation go down as well. Thirdly, medical conditions such as endometriosis or hydrosalpinx can affect the implantation negatively. The same refers to uterine cavity alterations, such as polyps or fibroids. In any case, when there is the so-called ‘disturbing’ factor in the uterine cavity, the embryo will have a lower chance of implanting. Fourthly, inappropriate endometrium development can also result in a decreased implantation rate. Here the conclusion seems obvious: in order to boost the implantation rate, we have to put the embryo in the best endometrium and in the best conditions possible.
Immunological causes of embryo implantation failure
Among all factors that affect the embryo implantation process and – consequently – reduce its chances of success, immunological alterations seem like the most common problem. According to dr. Marbán Bermejo, immunology and reproduction are really closely related. The first issue to consider in the case of immunological disorders is the presence of anti-thyroid antibodies. Dr. Marbán Bermejo always asks her patients to test a thyroid-stimulating hormone (TSH) level as well as some antibodies (anti TPO AB). If the latter is positive and the TSH level is over 2.5, there is a need of introducing a specific treatment called Levothyroxine (Euthyrox®). It is very important for anti-thyroid antibodies to be under really strict control – otherwise, the risk of having a miscarriage or a failure of implantation is significantly increased. The same happens with antiphospholipid syndrome (APS) – there are some basic antibodies to be tested, such as e.g. antinuclear antibodies (ANAs), anticardiolipin antibodies and lupus anticoagulant. Patients that test positive for these antibodies generally have a history of previous miscarriages or even thrombosis. In such a situation, it is really important to do a proper treatment followed by Aspirin or Heparin (or both) to decrease the risk of having another miscarriage or even a failure of implantation.
Dr. Marbán Bermejo describes pregnancy as a procedure with immune tolerance. The immune tolerance in such a case is the absence of a maternal response towards the foetus – meaning that the woman’s body doesn’t react negatively to the new human being. However, there are some patients who don’t have a very well-balanced immune system – and this results in natural killer cells (NK) expansion in blood or in the uterus. Such patients have a higher chance of having a pregnancy loss or an implantation failure. Dr. Marbán Bermejo says that when such patients are identified, they are contacted with an immunologist who decides about the best type of immunotherapy which may include corticoids, intralipids or gammaglobulines. All of the latter have proven to increase implantation and pregnancy rates.
Another part of immunological system is the combination of HLA and killer cell immunoglobulin–like receptor (KIR) genes that have been associated with diseases such as autoimmunity, viral infections, reproductive failure and even cancer. If patients are lacking most or all activating KIR (AA genotype) – and the foetus possess HLA-C belonging to the HLA-C2 group – they are at risk of implantation failure, recurrent pregnancy loss and some pregnancy complications, such as high blood pressure, preeclampsia or intrauterine growth restriction. To avoid the risk, the patients going for egg donation treatment should have their donors selected in the relation to the immune system. Patients planning IVF with their own eggs can have an immunomodulator treatment added. It is equally important to choose a single embryo transfer – otherwise, in case of transferring two embryos, the patient is put at risk of a double load of HLAC. And this may provoke an even stronger reaction from the immune system.
Dr. Marbán Bermejo also mentions celiac disease as one of the important immunological disorders endangering a successful pregnancy. The disease is caused by an intolerance to gluten and is especially risky in the case of patients who were left untreated or who haven’t been diagnosed yet. Apart from well-known digestive alterations, this disease can be related to the failure of implantation and miscarriages. That’s why it is important to test some antibodies against celiac diseases (anti-tissue transglutaminase and anti-gliadin antibodies) to make sure that they are negative. In case they are positive, patients – especially those with a history of implantation failures and miscarriages – should follow a gluten-free diet to have their results improved.
The role of endometrium in the embryo implantation
According to dr. Esther Marbán Bermejo, inappropriate endometrial development can reduce pregnancy and implantation rates. Desired endometrium should be between 7 and 12 millimetres thick and have triple-line pattern. However, some patients can have problems with achieving these ideal parameters before the embryo transfer. In such a case, doctors can prepare their endometrium – either by taking advantage of their natural cycle (and oestrogen pills) or by using some specific treatments, such as gonadotropins, Aspirin, Viagra or Pentoxifylline.
Another issue related to the endometrium is the window of implantation (or endometrial receptivity). It is known as the period of time when the endometrium has the best conditions for embryo implantation. In most cases, it happens between the 19th and 21st day of the natural cycle. However, dr. Esther Marbán Bermejo admits that 30% of patients have the window of implantation displaced. Fortunately, nowadays there is the opportunity of testing the endometrial receptivity to ensure a personalised embryo transfer at the correct moment. The test – called EndomeTRIO – can also be used for analysing endometrial microbiota and chronic endometritis. In case it shows any kind of inflammation or the lack of beneficial lactobacillus bacteria in the endometrium, some specific antibiotics treatment should be introduced.
Uterine and blood clotting reasons for a failure
Clotting alterations is another, after immunological disorders, serious cause of implantation failures. Dr. Marbán Bermejo says that one of the most typical and most common tests that she asks her patients to do are hereditary trombophilias (Factor V Laden, F II Mutation, MTHFR Mutation, F XII Mutation). The same refers to PROTEINE C AND/OR PROTEINE S DEFICIENCY and ANTITHROMBIN (AT) III DEFICIENCY. In case doctors find any of those alterations, they send the patients to a haematologist who adds some specific treatments such as Heparin or Aspirin (or both) in order to avoid affecting the implantation procedure.
Dr. Marbán Bermejo stresses the importance of the uterine environment for the success of the embryo implantation. That’s why all possible uterine alterations should always be closely assessed and dealt with – mostly with surgeries. These include intracavitary alterations (such as fibroids) that can be diagnosed using a vaginal scan complemented with 3D ultrasound and Asherman’s syndrome caused by post-surgery scars in the uterine cavity (and observed during a hysteroscopy). Another type of uterine alterations is hydrosalpinx which refers to a fallopian tube blocked with liquid that can be toxic for embryos. This condition is most commonly diagnosed with a scan and removed with salpingectomy (fallopian tubes removal). Uterine malformations, on the other hand, can be diagnosed and treated with a hysteroscopy. According to dr. Marbán Bermejo, the latter can be used for a successful removing of a uterine septum and – as a result – increasing the chances of embryo implantation.
The importance of the male factor
As all the mentioned factors relate closely to the female side of the reproduction process, male causes should be taken into account as well. Surely, it is important to conduct semen assessment, including basic semen analysis ( volume, concentration, motility and morphology) as well as more specific tests. One of them is single/double stranded DNA fragmentation test (Comet FertilityTM ). A high rate of single stranded DNA fragmentation is connected to a lower fertilisation rate while a high rate of double stranded DNA fragmentation results in higher chromosomal alterations risk in the embryo. In the end, both types of fragmentation lead to lower chances of successful embryo implantation. Dr. Marbán Bermejo says that, depending on the alterations found during this test, the specific treatment should be added to reduce the fragmentation. Doctors can introduce antioxidants or turmeric and recommend a healthy lifestyle (without smoking, alcohol and excessive coffee intake).
Another important issue in assessing the male factor is genetic semen tests: Chromosperm and FISH. There are several techniques to check the chromosomal content of the sperm – and this is crucial while DNA alterations in the sperm lead to a higher number of non-healthy embryos.
The embryo and its quality
Dr. Esther Marbán Bermejo admits that one of the most important factors for successful embryo implantation is the embryo itself. Its classification should be conducted according to the criteria such as cell number, the percentage of fragmentation, nucleation, alterations and cell division moment. In order to determine the latter and understand how embryos are dividing, new technologies as Time-Lapse incubators are used.
In dr. Marbán Bermejo’s opinion, the embryo quality is the aspect doctors should always pay most attention to. It should always be good or – at least – intermediate. The embryo has to be well-developed, with regular cells, and chromosomally healthy. The latter feature is, in fact, the most important. It is true that the older the woman gets, the more unhealthy embryos she will have. That is why the role of pre-implantation genetic screening (PGS) is so crucial here. It helps to exclude chromosomally abnormal embryos and choose the ones that may help in increasing pregnancy and implantation rates.
After the embryo transfer
In order to increase the chances of the embryo implantation success, dr. Esther Marbán Bermejo gives patients some recommendations regarding proper behaviour after the embryo transfer. According to her, it is important to avoid intense physical activity and sexual intercourses and follow all the prescribed medications – to maintain the endometrium in an unchanged state. Some bad habits, such as drinking alcohol and smoking, will not prove beneficial either – so it is necessary to restrain from them straight after the transfer and during pregnancy. All of this may help increase the embryo implantation rate as much as possible – and help patients make an important step towards the dream of parenthood.