As a rule, it is rather difficult to pinpoint when the egg was fertilized, so the beginning of pregnancy starts counting from the date of the beginning of the last menstrual cycle.
Fertilization
From this time begins the formation and subsequent maturation of the egg. Her fertilization occurs within one to two weeks.
Before the male and female reproductive cells meet, it will take 3-6 hours. Numerous spermatozoa, moving towards the egg, meet on their way a lot of obstacles, as a result, only the most powerful spermatozoa get to the goal. But only one of them will participate in the process of fertilization.
When the spermatozoon overcomes the coating of the egg, then immediately the woman's body begins to rebuild its work, which will now be aimed at maintaining the pregnancy.
In the process of fertilization, a new cell with its own genetic code, which will determine the sex of the child, its shape of the ears, the color of the eyes and other features, is formed from two parents' cells, each having half a set of chromosomes each.
On the 4th - 5th day, the fertilized egg reaches the uterus. By this time, it is already developing into an embryo consisting of about 100 cells.
Implantation into the wall of the uterus occurs at the beginning of the third week. After this conception is completed. Movement to the uterus and attachment to its wall is the most dangerous stage of fetal development in the first month.
Formation of the fetus
In the first month after the end of the implantation process, active fetal formation begins. The chorion begins - the future placenta, the amnion - the precursor of the fetal bladder and umbilical cord. Development of the fetus in the first month of pregnancy begins with the formation of three embryonic leaflets. Each of them represents an embryo of separate organs and tissues.
- The external embryonic leaf is a rudiment of the nervous system, teeth, skin, ears, epithelium of the eyes, nose, nails and hair.
- The middle germinal leaf serves as the basis of the chord (skeletal muscles, internal organs, spine, cartilage, vessels, blood, lymph, sex glands).
- The internal embryonic leaf serves as a basis for the formation of the mucous membrane of the respiratory system, the organs of the gastrointestinal tract, the liver and the pancreas.
By the end of 1 month of pregnancy, the fetus (embryo) already has a length of 1 mm (the embryo is visible to the naked eye). There is a bookmark of the chord - the future spine. There is a bookmark of the heart and the appearance of the first blood vessels.