As you know, the entire gestation period is divided into so-called trimesters - a time interval, the duration of which is exactly 3 months. Consider this parameter in detail and understand: 1 trimester of pregnancy - how many weeks it is, and what major changes occur in it.
How long is the first trimester of gestation?
As already mentioned above, 1 trimester - 3 months. If you try to translate it in weeks and find out: how long the first trimester of pregnancy lasts, then it turns out that this is in general 12 obstetric weeks.
What happens to the fetus at this stage?
At the beginning of pregnancy, the future fetus is a small accumulation of cells that are constantly divided. At the stage of gastrulation, the introduction of the fetal egg into the uterine endometrium takes place. It is from this time, in fact, the very beginning of pregnancy.
By the middle of the second week, the nervous system of the future baby begins to form, and closer to 4, the eye cavities are formed, the arms and legs of the unborn child begin to differ. By the end of 1 month of pregnancy, the embryo is still very small, only 4 mm.
In the 2nd month of gestation, a fairly active development of the brain is noted. In this case, the head of the embryo itself is large enough and in its size exceeds 1/3 of the length of its trunk. The future baby looks like a big hook.
At this stage of development, the heart is already actively contracting. At the place where the ears and eyes will be located, some kind of compaction is formed, which are the rudiments of these organs. Towards the end of 2 months the organs of the reproductive system of the embryo begin to form. However, it is still impossible to determine the gender. The size of a small organism at this time does not exceed 2.5 cm.
3 month gestation is characterized by the appearance of some contours of the face. In this case, brushes and feet are already different. Finally, by this time, the organs forming the gastrointestinal tract are formed, in particular the liver, stomach, intestine. The formation of the respiratory system also takes place.
The heart is already 4-chambered, the network of blood vessels grows. There are changes in the brain: grooves and convolutions are formed. There is a gradual replacement of cartilages with bones, which contributes to a more active movement of the baby. Some women, which are more characteristic of the moles, can mark the first movements at the end of the first trimester .