Why the embryos do not implant?

This is a million-dollar question. When we transfer the embryos, we basically lose control of what’s going on. There could be different reasons why the embryo does not implant. It could be that the initially good embryo stops developing because of some genetic condition, abnormal development of the cells and the embryo is no longer viable, and it does not implant. It could also happen that the dialogue that takes place between the embryo and the endometrium does not take place properly. The embryo cannot really implant as it should and that at some stage, the embryo may lack the necessary things to keep on growing. This may also end up in a negative.

It could also be that there is something wrong on the patient’s side, on the endometrium level, antibodies, coagulation issues, for example, that may make it more difficult for the embryo to implant. If we transfer the embryos, and we won’t get single implantation even if we think that the embryos were of good quality, it’s going to make sense to carry out some studies to see if there is anything wrong on the mother’s side.

Now this is a very good question but I would say this is a million dollar question: why embryos do not implant?
In general, though, we have to consider that reproduction and implantation is like an orchestra – many things have to go well at the same time and many things have to be synchronized. Successful implantation requires a good quality embryo, a receptive endometrium and a quite functional uterus, again, we simply don’t know why some embryos fail to implant but most are related to embryo quality and the receptivity of the uterine lining.
When it comes to an embryo, there could be many or few genetic defects that could cause implantation failure. Just keep in mind that our 46 chromosomes contain around 20 to 25 000 genes that they have to function properly to have the embryo develop successfully. Again, think it like a symphony of the genes being turned on and off to allow implantation, we think that gene malfunction is a quite common cause of good and decent quality embryos not implanting.
Endometrium as well is another factor. Embryo implantation it’s definitely not the passive process, the endometrium and the embryo exchange a lot of messages and they have a kind of crosstalk between each other. New developments in the receptivity of the endometrium are coming out and these are quite promising to allow an assessment of the endometrium prior to implantation. It proves that again that the endometrium is a very significant factor when we have quite poor embryos and implantation and creating a life-birth.

To achieve pregnancy, we need good quality embryos. We also need a healthy uterus, healthy endometrium, which is the internal part of the uterus. Usually, implantation occurs according to women’s menstrual cycle. The period when the endometrium is ready to implant the embryo is called the implantation window. It usually lasts for 24 hours to implant the embryo. It is necessary to coordinate women’s menstrual cycle after ovulation and embryo stage.

Usually, on the 5 -day embryo, the blastocyst is available for the uterus on day-5 after a progesterone intake, but sometimes this implantation window deviated to the right or left side. An ERA test or endometrial receptivity test can help us with detecting the implantation period. The implantation is based on 239 gene expression in the endometrium, not only in endometrial and morphological changes.