Implantation of the embryo in the uterus. What happens after fertilization?

After fertilization, the egg is waiting for a long and complex path to implantation into the endometrium of the uterus. According to statistics, more than half of them will not pass. At the same time, a woman does not even know that a new life has begun in her.

On average, implantation of the embryo occurs one week after fertilization. All this time the egg moves along the fallopian tubes and actively develops, preparing for this event. After 20 hours after fertilization, it is divided into two parts. After this, the ovum is already called a zygote. During its journey, it is divided many times to form a solid ball of many cells. When their number reaches 16-32, the zygote becomes a morula. If it is divided into two parts, then the twins will be obtained. When the morula reaches the uterus, then there is an average of 64 cells. Some of them will develop into the fetus, and the rest will form membranes and placenta.

Morula gradually turns into a liquid-filled ball. After that she is a blastocyst. The surface layer of cells will become the placenta, and those that are inside will develop into an embryo. It is in the blastocyst stage that a fertilized egg enters the uterus.

This is normal, but if the fallopian tubes are impassable for some reason, embryo implantation can occur directly into their wall. There comes an ectopic pregnancy, which poses a danger not only for the woman's reproductive health, but also for her life.

How successful is the implantation of the embryo into the uterus depends on whether the latter is ready for this. Getting into it, the blastocyst develops for several days in free swimming. In the preparation of the uterus for implantation, the main role is played by the hormone progesterone.

The thickness and sensitivity of the endometrium is very important here, since embryos that begin interacting with it are not implanted if they are not ready for it. The most successful time for the introduction of the blastocyst into the uterus is the period from the 20th to the 24th day of the menstrual cycle. At that time, the endometrium is most susceptible to it, since a large number of active substances are produced.

A blastocyst during penetration penetrates into it by cells, and a tissue rupture occurs with the release of blood. Sometimes the endometrium is not nutritious enough for her, then a miscarriage occurs.

In case the implantation of the embryo has not been successful, it is excreted through the vagina. According to statistics, about 40% of the blastocysts that get into the uterus do not penetrate into its mucosa.

If the implantation was successful, then the development of the placenta and the development of an embryo hormone pregnancy hCG.He needs about 2 weeks to gain a foothold in the uterus. During this period, miscarriage is possible, but not as likely as immediately after implantation.

Some organs and systems of the embryo are already being formed. In these two weeks it is still possible to divide it into two parts and form two fruits. If it happens later, the Siamese twins are obtained.

Many future mothers are interested in, perhaps, to know that implantation has occurred. It turns out that there are a few signs that this happened. So, implantation of the embryo: symptoms:

  • possible bleeding;
  • on the graph of basal temperature there is its sharp decrease( implantation sinking) on ​​this day.

This is due to the fact that after the introduction of blastocysts into the endometrium, there is a sharp release of estrogen, which leads to a decrease in temperature. By the way, it is because of it in the first phase of the cycle, it is low.

Thus, implantation of the embryo is accompanied by a decrease in basal temperature and in some with slight bleeding. According to statistics, it occurs successfully only in 60% of blastocysts, and the rest are excreted. A very dangerous pathology is its attachment to the wall of the uterine tube with its obstruction. The journey and development of a fertilized egg lasts about a week. For the successful implantation, the sensitivity and thickness of the endometrium is very important.