Implantation: how does this happen?
Nesting is an essential step in the course of pregnancy. After the famous encounter between the spermatozoon and the ovum, it is the essential prerequisite for the development of the future baby: the embryo is implanted firmly in the uterine lining and can continue its development. Focus on this critical moment!
From fertilization to implantation Everything
Begins with the fertilization of an ovum by a spermatozoon. The egg thus constituted is still only a few tenths of a millimeter, but it is already starting a long journey, from the fallopian tube, where it has been fertilized, to the uterus, where it is to be implanted. Its progression is facilitated by the contractions of the trunk and by the movements of the lashes which cover it. This stage lasts between 3 and four days. Once in the uterus, the egg remains there for a few days at liberty, then it clings to the mucous membrane, or endometrium, to make its nest there.
Note: this nidation takes place in the vast majority of cases (more than 99%) in the uterine mucosa. However, it may happen that the egg settles elsewhere, especially in the trunk: This is called ectopic pregnancy. In this case, this is manifested by intense pain in the lower abdomen, sometimes accompanied by bleeding. It is, therefore, necessary to consult an emergency gynecologist.
The actual nesting
It occurs about 6 to 7 days after fertilization. The fertilized egg separates into two parts. The first part will bury itself in the uterine mucosa to hang there firmly: it is the trophoblast or future placenta (also called corpus luteum). To do this, he begins to secrete enzymes that will allow him to dig the membrane, then connects to the vessels of the mucosa. The future placenta also has the role of neutralizing the antibodies produced by the mother’s organism (which then considers the egg as a foreign body), to protect the egg.
Once the nidation is complete, the cells of the future placenta begin to produce the hormone HCG or pregnancy hormone. It will be detected during a urinary or blood pregnancy test: if it is present, it means that the fertilized egg has been implanted in your uterine lining and that you are pregnant. Early signs of pregnancy, including nausea, may occur from this point on.
Does the nesting succeed every time?
Approximately one in two fertilized eggs succeeds in this stage of the nidation. The others are eliminated naturally by the body of the woman, without even noticing it, during the following rules. Hence, sometimes, a delay of rules.
The reasons for this implementation failure can be very diverse. They may be linked in particular to a chromosomal abnormality of the egg or a problem of the mucosa (membrane too thin, the presence of polyps …).
How do you feel when nesting?
Some women report feeling cramping or tightness in the lower abdomen at the time of nesting, similar to how you feel during menstruation. These pains, more or less intense, may be accompanied by a rise or fall in body temperature.
At the time of nesting, small pink or brown bleeds are also possible. They are precisely related to the nidation. When the egg clings to the uterine lining, it can cause the rupture of small blood vessels, which can cause these little blood loss. This has no impact on the future course of pregnancy.