Following on from our recent Implantation blog, this post will look at implantation failure.
Implantation is still not completely understood. There exists a complex cross talk between the embryo and the endometrium that requires a perfect synchronization for successful implantation. With the advent of genetic testing and screening of embryos, it is now possible to identify the implantation rate of chromosomally normal or “euploid” embryos. When embryos are chromosomally normal, implanatation rates are 70%. So what other factors play a role in this important phase of establishing a pregnancy?
The endometrium is not just a cushiony bed for an embryo to find its home. It is an active tissue continually changing to meet the needs of the growing embryo. The timing for the embryo to find its endometrial bed is precise with the “window of implantation” existing for only 6-10 days after ovulation. This ensures the right type of cells, their secretions (known as the “secrotome” in the scientific community), and genetic expression is optimal.
Why won’t you stick?
Abnormal embryos: By far the most common reason for recurrent implantation failure falls on the quality and chromosomes of the embryo. Science has progressed in leaps and bounds in this area and it is now possible to test embryos before they are transferred improving the pregnancy chances significantly.
Anatomy: It is worthwhile ensuring your specialist has thoroughly investigated for the presence of polyps, enlarged, fluid-filled tubes (known as hydrosalpinges), fibroids, endometriosis, an abnormally shaped uterus or scar tissue which may impede implantation
Immunological disorders: There is some evidence that immunological conditions that alter the balance of tolerance and rejection of an embryo can interfere with implantation. Although many treatments have been studied, the evidence for many is controversial. Use of heparin, aspirin, prednisolone, immunoglobulin are medications that are sometimes used, but there are also detrimental effects with these medications and caution is recommended under the guidance of fertility specialist should they be prescribed.
Medical conditions: There are some conditions in which the endometrium (your uterine lining) is affected by medical conditions. Blood flow is an important factor in growing your lining and there are some disorders in which this is suboptimal. Again it is an area of contention with regard to treatment.
Unknown: This is the most difficult to “diagnose” and manage. An expectation always exists in being able to find a reason and then provide a solution. Our understanding of implantation is in its infancy and how we might affect it remains one of the great frontiers in reproduction. This is why treatment is difficult, as there is limited evidence that any of the treatments we have on offer are beneficial.
Recurrent implantation failure is an area of intense research interest and the focus of many infertility studies. There is hope that science may start to decode some of the conversation that exists between the embryo and endometrium and help improve implantation rates.