Once sperm and egg unite, the embryo is formed. It constitutes a cell with the complete genetic load, contributed by both parents. This process is known as fertilization and in most cases it takes place inside the fallopian tubes.
The embryo must travel towards the uterus, to implant in the endometrium, which is a mucous layer that lines the uterine cavity. In this way the nesting or implantation of the embryo, a fundamental fact for pregnancy to occur.
How does the implantation of the embryo occur?
Once the egg is fertilized, it must travel to the uterus. This process takes an average of 6 to 7 days and corresponds to day 20 to 24 of the woman's cycle.
During this period the endometrium undergoes some changes that prepare it for nesting. This is due to hormonal action, as well as the presence on the surface of the embryo of a series of molecules that allow it to adhere to the endometrium. It is essential that during this process the embryo is placed on the endometrium and penetrates it, reaching the mother's blood vessels.
Nesting usually occurs on the posterior aspect of the uterine cavity. During this process there are no symptoms or discomfort that the woman can show.
Not all embryos manage to nest or implant properly
Many times, once the egg is fertilized, it fails to implant. The factors related to this fact are not fully understood.
It is estimated that only 3 out of 10 fertilized eggs manage to implant properly, thus giving rise to a pregnancy. The reasons that lead to these are many, including hormonal disorders, changes in the uterine cavity and the age of the woman.
Several substances produced by the immune system have a regulatory role in implantation. These substances are released by stimuli from the embryo itself and are intended to achieve adhesion of the embryo to the endometrium.
Nesting or implantation of the embryo is a critical phase for pregnancy to be achieved. This can be influenced by external factors such as emotional stress, physical exhaustion, as well as by substances that include medications, drugs and alcohol.
Abnormal embryo implantation
Sometimes the embryo implants in the fallopian tube. This is what is known as ectopic pregnancy.
Since the tube is not the indicated place to nest the embryo, once it begins to grow it can cause the tube to rupture which produces a very intense pain accompanied by hemorrhage, which is located in the lower abdomen towards one from the sides. When it occurs on the right side, it can be confused with appendicitis.
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