Implantation is the final step that an embryo must go through to “nest” inside the maternal uterus and grow until it becomes a foetus. During this process, many factors come into play – internal as much as external – which are responsible for ensuring the correct development of the embryo.
Thanks to the techniques and research in the world of assisted reproduction, improving embryo implantation rates is certainly possible. To achieve this, we can program the timing of implantation so that the endometrium is in the correct receptive state at the same moment that the blastocyst is ready for transfer. Embryo implantation takes place approximately 4 to 5 days after it has been transferred into the uterus. If symptoms are felt, the most common are; brown or red spotting when the embryo is implanting, breast swelling and tenderness, dizziness, feelings of angst and an increased urge to urinate, among others. Approximately 10 days after the embryo transfer a beta hCG+ test is performed to confirm the pregnancy. But, what happens if it doesn´t work and you have multiple implantation failures?
For the egg cell to be fertilized, it needs to have certain characteristics at a specific moment in time. The same occurs for the endometrium, but with the difference that we have the egg cell under a microscope to study it, while for the endometrium, we have to use another way to look at it. To study it, we use indirect methods – progesterone and endometrial imaging – to know whether it is receptive, to be able to transfer the embryo when it is in the right stage of development for transfer. Sometimes, the embryo is ready when the endometrium is not in an adequate state. If this happens, we should cryopreserve the embryos until the right moment for the transfer. We have to prepare the endometrium and when it presents with the ideal conditions, transfer the embryo we have available, that had been cryopreserved. This is known as a delayed, or deferred embryo transfer.
Endometrial tests to obtain the best possible results
Another option that we have is to prepare the endometrium as if for an frozen embryo transfer and once the correct moment has arrived, perform a series of tests known as the EndomeTRIO (ERA, EMMA and ALICE tests) instead of the transfer. These tests allow us to study the health of the endometrium in depth, analysing the endometrial receptivity, the endometrial microbiome, and to detect any bacteria that could be causing inflammation of the endometrium, and as such be the reason for the implantation failures.
This process means that in order to do the embryo transfer, a repeat the cycle of endometrial preparation is required. It is a process that means more time and costs, but at the same time gives us the benefit of more certainty that we are performing the embryo transfer at the best moment to achieve the best possible results.