Embryo implantation, the ultimate test
It’s the miracle of life: fertilization and human reproduction. A meticulous and perfect process that allows two cells to come together and create another that will develop until transforming into a new being.
Since the beginning of mankind, the ability to create life has been considered an object of worship. Similarly, the difficulty in achieving motherhood, especially when there are failed attempts, is a source of frustration for parents. But science once again progresses to offer answers and solutions. And nowadays, thanks to technological advances and innovation in assisted reproduction, we precisely know each step of fertilization, a fact that helps us to understand the reasons why occasionally and sometimes repeatedly it does not end in a healthy and viable pregnancy.
It all starts when out of hundreds of thousands of sperm only one successfully reaches the egg in one of the fallopian tubes and fertilizes it, creating a new cell: the zygote. During the following days, it begins to slowly descend into the uterus where it must pass a crucial test of extraordinary complexity: embryo implantation.
Implantation is the adherence to the uterus, which allows the future fetus to obtain oxygen and nutrients from the mother for its proper development and growth. But in order for this implantation to be effective, the zygote must be strong enough to attach, the uterus must be prepared to receive it and also the communication between them must be adequate. Therefore, sometimes if one of these steps does not occur, the implantation may not take place successfully. Only 1 out of 4 embryos successfully implants in the uterus, so this first test for the embryo is “the great unknown challenge”, as explained by the specialists of Instituto Bernabeu Alicante.
If this situation is repeated several times we could be facing an implantation failure, which refers to those patients who do not achieve pregnancy after several treatments of In Vitro Fertilization (IVF), such as those who have done one but then have repeated early miscarriages. There are several reasons that could explain this fact. On the one hand, the answer might be in the embryo itself and its composition. Keep in mind that is a strange element to the maternal immune system because it does not have the same constitution of proteins and tissues as the mother, since it also contains the father’s cells. For this reason, the maternal immune system will try to reject it since it detects foreign matter. The embryo must therefore resist the mother’s possible immune system attack, which will sometimes prevent its implantation and subsequent pregnancy. Besides the embryo factor, there are also maternal and paternal factors involved in causing implantation failure and repeat miscarriages.
Science, research and technological advances are now allies to understanding these factors and allowing for appropriate treatments and specific solutions to overcome them. In this regard, the Implantation Failure Unit of Instituto Bernabeu studies each particular case with a team of doctors, embryologists and molecular biologists. “We have developed a program with specific protocols to treat repeat miscarriages and unsuccessful assisted reproduction treatments. Through a multidisciplinary approach, we can diagnose and therefore successfully treat these problems”, explains Dr. Rafael Bernabeu, medical director of Instituto Bernabeu Alicante.
“The maternal contribution is the most complex”, as explained at Instituto Bernabeu Alicante. Thus, the Implantation Failure Unit observes the uterus and any factor affecting the uterine receptivity is ruled out. Moreover, thanks to a new ultrasound system, the endometrial volume and vascularity are measured, which are also critical in determining the uterine capacity for implantation. The ovaries are also studied to check that there is no condition that would prevent the embryo implantation. Regarding the paternal factors, it is essential to know “the percentage of sperm carrying fragmented DNA and chromosomes, since it allows us to narrow down on the details of the father’s contribution to the future embryo”, explain the IB specialists.
In addition, both the mother’s and the father’s chromosomes are studied because they contain the hereditary load that the embryo will receive. The transfer of chromosomally normal embryos will drastically reduce the risk of miscarriage. In this regard, a new technique is being applied, the Array-CGH, which detects any DNA alteration at a much more sensitive and precise level, allowing us to reach diagnostic levels 10 times higher than the previous tests.
Continued embryo implantation failure or repeated cases of miscarriage when the embryo had already nested in the uterus for weeks are situations that can create frustration in the couple but can currently be solved thanks to scientific innovation and technology applied to assisted reproduction.
These advances allow us to better understand the mother’s uterus and the father’s sperm with a precision unthinkable a few years ago and also provide us with new genetic information of the embryo, the star of the human fertilization process. Cutting-edge tests, detailed DNA information, increasingly specialized professionals and new precise assisted reproduction techniques come together with one shared goal: getting a group of cells to find their place in the womb, develop and transform into a new being.