Non-receptive endometrium: This happens in very few patients, in whom the endometrium is not receptive in the usual days of the transfer. For this we can perform an endometrial biopsy and look for which days the endometrium is more receptive to transfer the embryos. Endometrial biopsy allows us to genetically study the endometrium of our patients.
Thrombophilias: Thrombophilias, in general, are conditions that interfere with the blood clotting process and increase the risk of thrombosis. These can be congenital or acquired. The association between congenital thrombophilias and implantation failure is weak. However, they should be investigated especially if there is a family or personal history of thrombotic events. Among the acquired thrombophilias, the most important for pregnancy is Antiphospholipid Syndrome, because in addition to increasing the risk of thrombosis, it increases the risk of suffering complications such as pre-eclampsia-eclampsia and miscarriage. It has also been shown that antiphospholipid antibodies can directly interfere with the implantation process and embryo development. Early diagnosis and treatment can improve outcomes and reduce complications.
Immunological alterations: The immune system is essential for human reproduction. In the endometrium, natural killer (NK) lymphocytes are specialised cells that, far from attacking the embryo as their name suggests, under normal conditions favour implantation and the early development of the placenta. These cells are endowed with immunoglobulin-like receptors (KIR) that allow them to interact with molecules expressed by the embryo (HLA-C). A certain combination of KIR receptors known as the AA genotype has been shown to increase the risk of implantation failure, repeat miscarriages, pre-eclampsia and intrauterine growth restriction (IUGR).
On the other hand, in certain circumstances, the mechanisms that prevent the immune system from attacking our own body fail, and antibodies are produced against our own cells or tissues (autoantibodies) giving rise to what we know as autoimmune diseases. The presence of anti-thyroid antibodies, for example, has been associated with a lower probability of having a live birth, a higher probability of miscarriage and in some cases a lower implantation rate in the context of assisted reproduction.
Additionally, systemic autoimmune diseases such as Lupus are frequently associated with anti-phospholipid antibodies that can have a negative effect on the outcome of assisted reproductive techniques and the evolution of pregnancy.
Finally, another autoimmune disease, celiac disease, has been linked to implantation failure. In patients with positive antibodies for celiac disease, a gluten-free diet may improve the outcome of assisted fertilisation techniques.
Although immunological alterations are not the most frequent cause of reproductive failure, their relevance increases in cases of reproductive failure of unexplained cause or when genetically healthy embryos have been transferred without achieving pregnancy. That is why we offer our patients, when required, the most advanced immunological diagnostic techniques and the possibility of receiving specific treatment if any alteration is identified.
Anatomical alterations: The presence of fibroids or malformations in the uterus could make implantation difficult. Hysteroscopy can solve most problems.