The fertilized egg makes a difficult way to get into the uterus - the place where it will develop throughout the pregnancy. In the uterus, the egg enters the blastocyst stage. Blastocyst is a ball filled with liquid. The outer layer of the blastocyst will eventually grow into the placenta, and the cells inside become an embryo. Now she has to undergo the implantation process, which means embryo attachment to the uterus. It is after the completion of implantation that pregnancy is considered to have come.
Terms of embryo implantation
Once in the uterus, the embryo is in free floating for several days, and then the implantation process begins immediately. The so-called implantation window comes on 6-8 days after ovulation. Implantation of the embryo into the wall of the uterus takes place on the 5th-10th day after fertilization. The embryo must fully integrate with the body of the mother. On average, the embryo needs about 13 days to firmly entrenched in the uterus. At a time when the embryo is attached to the uterus, a woman may have slight bloody discharge. This is due to the attachment of the embryo to the uterus. During this entire period there is a high probability of miscarriage.
For successful conception in the body, women should coincide with the implantation window, the readiness of the uterus to accept the embryo, and the presence of an ovum that has reached the blastocyst stage. After the blastocyst is attached, the formation of the embryo directly depends on the mother's body. Now they have a very close relationship with each other.
Why there is no embryo implantation?
As is known, about 40% of blastocysts that successfully entered the uterus are not implanted. One of the reasons that the embryo is rejected is a violation in the endometrium - the so-called uterine membrane. This membrane may not be nutritious enough for a blastocyst. Or it has any deviations. Very often, abortion is the cause of abnormalities in the endometrium. As a result of such abnormalities, miscarriages occur. In this case, many women do not even guess about conception, because a fertilized egg leaves with the next monthly.
Classification of embryos
Classification of embryos used clinics that are engaged in IVF fertilization. Each clinic has its own classification. However, the most common of these is the alphanumeric classification.
The classification mainly assesses the quality and appearance of the embryo. The main characteristic in the classification of embryos on the 2nd and 3rd days of development is the number of cells, as well as their quality.
A qualitative embryo should contain the following number of cells:
- for 2 days - from 2 to 6 cells;
- for 3 days - from 4 to 10 cells;
- for 4 days - more than 8 cells.
Figures in the classification indicate the size of the blastocyst, as well as the stage of expansion. There are 1 to 6 stages. In some clinics, I also indicate the number of cells in numbers.
The first letter used in the classification indicates the quality of the internal mass of the cell, from which the embryo develops. It is accepted to distinguish the following stages - A, B, C, D, of which A is the most favorable.
The second letter indicates the quality of the trophoblast - this is the outer layer of the blastocyst. It is this layer
Using the classification of embryos, the centers of artificial insemination determine precisely the cell that is able to attach itself to the epithelium of the uterus in the best way. It is from her that a healthy and full-fledged embryo will subsequently develop. After the implantation process is completed, the active process of embryo growth inside the mother begins.