In the process of development of the fetus taken to distinguish between two periods:

1) embryonic or fetal period, continuing from the moment fertilization up to 8 weeks of pregnancy;

2) fetal, or fruit, a period lasting from 8 weeks of pregnancy until moment of birth.

Although the embryonic period lasts only 2 months, it is the most important and most vulnerable in the life of fetus,since that time embryo is formed of all its major organs and systems -- organogenesis (ie, the emergence of bodies). During this period the embryo is extremely sensitive to the effects of adverse factors,which may lead to major malformations.

The first four weeks (from conception to two weeks of fetal life) Fruit After fertilization, the egg is quickly transformed from a single cell in set. Every half hour is a division into two cells, then four, eight, sixteen, etc.By the end of the second day of a clot is formed cells called morula. For five days Morula is on its way fallopian tube into the uterus and by the end of the first week is usually implanted (attached) in the upper part of the uterus. We formed blastocyst (as he now called) are developing thin "spines" (nap chorion), which penetrate the lining of the uterus and get food from there.

In the first weeks of pregnancy the mucous membrane of the uterus (endometrium) becomes thick and penetrated by blood vessels, providing nutrition developing blastocyte. By the end of the first month of nap chorionic penetrate deeply into the lining of the uterus and form a primitive placenta. Fetal blood circulates in the "roots", as your blood circulates between them (in intervillous space).Two streams of blood are separated by a thin membrane and in the normal course of pregnancy do not mix.

As a result of the complex process of division and differentiation of cells formed fetus, placenta, fetal bladder and amniotic fluid. Membranes surrounding blastocyte;later encased in a bubble liquid (amniotic fluid, or amniotic fluid) will protect the fetus against external shocks, maintain inside a constant temperature and ensure freedom of movement of the fetus. With the fifth fourteenth week of pregnancy (the third to the twelfth week of fetal life)