Embryo implantation is the final frontier to effective pregnancy. In the last decades, there have been enormous advances in the knowledge of human embryo development. Since the advent of In Vitro Fertilization (IVF), the embryo continues to be readily available to review outside the human body. Indeed, the research has brought to much advancement in embryonic stem cell derivation. Regrettably, it is not so easy to judge the steps of the embryo implantation, since most gynecological tools cannot access the uterus. It has limited clinicians’ knowledge of early embryo implantation.
Both physiological and pathological mechanisms of the embryo implantation occur largely unseen. The heterogeneity of those processes between species also limits clinicians’ capability to develop appropriate models to review. In humans, there is an exact coordinated timeline, where pregnancy can happen in the uterus, the so known as “window of implantation”. However, oftentimes the embryo implantation does not happen despite the optimal timing and the embryo quality. It is very frustrating to both clinician and a patient to transfer a high-graded embryo right into a well-stimulated uterus only to get it neglect to implant. This blog post is discussed several reasons why it does not occur.
The Phases of Human Embryo Implantation
The embryo goes to the uterus usually five days after fertilization being at blastocyst stage. Since passing through the fallopian tube, or perhaps a catheter, the embryo is moved inside the uterine lumen by the rhythmic myometrial contractions until it can physically attach itself towards the endometrial epithelium. It hatches from the zone pellucida within up to two days since entering the cavity, therefore exposing the trophoblastic cells of the trophectoderm towards the uterine epithelium. The embryo implantation occurs up to seven days after fertilization. Throughout the embryo implantation and placentation, the embryo must attach itself towards the uterus under conditions of shear stress. The embryo is rotating inside a mucus rich environment between the opposing surfaces of the endometrial walls of the uterus. This process is a complex set of events that can be split into three distinct steps such as apposition, attachment and invasion.
Optimizing Embryo Implantation
For the couples who are suffering from infertility, Assisted Reproductive Techniques (ART) are the most effective in overcoming nearly all barriers. The effectiveness of IVF is achieved by the opportunity to bypass certain obstacles e.g. low sperm counts or tubal disorder, and to find the most viable embryo to be put into the uterine cavity at the optimum time. The factors that limit IVF success can be generally distilled lower to the health of the embryo versus the health of the endometrium, or perhaps in essence an assessment of the seed in comparison to the soil.
Digging Inside the Failure of the Embryo Implantation
Due to the numerous reasons of infertility and early pregnancy loss, clinicians hypothesized that defects in the selectin adhesion system could take in mind some of inexplicable reproductive failures. Thus, there are subgroups of women undergoing IVF who repeatedly neglect to implant regardless of the transfer of high quality embryos. Clinicians’ goal was to assess whether the lack of the L-selectin ligand MECA-79 on the endometrium occurs more often in patients with Repeated Implantation Failure (RIF), and if the latter correlates with unsuccessful embryo implantation.
To conclude, the embryo implantation of the human embryo is a complex interaction in between the endometrium and the active blastocyst. It has to occur inside a relatively narrow period under conditions of the primed receptive surface epithelium along with a morphologically altering trophectoderm. Mechanically, the movement of the blastocyst should be stopped to ensure that attachment and then invasion can happen. The L-selectin ligand adhesion system is becoming more convincingly, thought to play a significant role in mediating initial embryonic apposition. By loose tethering, the blastocyst has the capacity to attach regardless of the shear forces inside the uterine lumen and orient itself for stable attachment. Once anchored, a cascade of events unfolds allowing the embryo to burrow into the endometrial wall and set up a hemochorial placenta.
Disorder in either the blastocyst or the endometrium itself can limit the embryo implantation efficiency. Many evidences have shown that improved selection of the embryo can drastically enhance the embryo implantation rate. As the endometrial side from the equation is much more difficult to worry about, clinicians are uncovering areas where proper preparation and resolution of a receptive endometrium is improving outcomes. Each phase across the embryo implantation process, and certain disease states, happen to be shown to disrupt the delicate dialogue needed for the embryo implantation. Concerning the apposition step, the L-selectin ligand can be utilized like a marker for the embryo implantation efficiency.
Clinically, in high-risk groups, the clinician could biopsy a patient and potentially prevent many futile attempts of pricey treatments if the ligand is absent. This could supply the patient with significant information why she is not able to get pregnant and open options e.g. egg donation or gestational surrogacy to assist her to become a mother. Beyond apposition, defects that disrupt integrin expression have been proven in disease states e.g. endometriosis and hydrosalpinges. Treatment of these defects have improved outcomes. Finally, the invasion of cytotrophoblasts towards the proper depth of the uterus is crucial in determining the pregnancy outcome. Excessive invasion results in placenta accreta, while insufficient invasion continues to be implicated in the pathophysiology of preeclampsia, the key reason for maternal mortality.
Normal embryo implantation is vital for successful pregnancy. For the infertile couple as well as their treating physician, a much better knowledge of the processes of the embryo implantation will enable better diagnosis and treatments to overcome the reasons of why they cannot possess a healthy child. Together, by selecting of the healthiest embryo and raising the most receptive endometrium, clinicians can boost the embryo implantation efficiency. Future research into markers of endometrial receptivity allows clinicians to define the optimal conditions to transfer the best embryos, therefore improving pregnancy rates and decreasing complications e.g. multiple pregnancies, miscarriages and eventually conditions that compromise the healthy intrauterine growth and development of baby.
Otherwise, as was noted above, cornerstone options e.g. egg donation or gestational surrogacy can help women to get happy moms. As the reputable market player in the field of reproductive medical tourism in Ukraine, Parents Life is pleased to offer you options e.g. egg donation or gestational surrogacy in order to treat your infertility problems!