What changes does the fetus undergo?
Externally, the fetal egg is gradually transformed into an embryo. The internal structure of it also becomes more complicated. Now it resembles a disk consisting of immediately 3 layers of cells of the same size. In embryology, they are commonly referred to as embryonic sheets. Immediately given anatomical structures give rise to individual systems and organs of the unborn child.
The outer, or as it is often called the outer layer, is the ectoderm. Directly from it are formed such structures as:
- skin integument;
- hair;
- nails.
In addition, the outer leaf takes a direct part in the formation of the nervous system, the visual apparatus, teeth.
The middle layer, the mesoderm, gives rise to the bone system, connective tissues, the muscular apparatus, excretory, genital and circulatory systems.
Endoderm, the inner layer, is the basis for the formation of the gastrointestinal tract, the liver, the glands of internal secretion.
At obstetric pregnancy 4 weeks, at the point of attachment of the fetal egg to the uterine wall, a network of blood vessels begins to form. It is she who gives rise to the placenta.
Is it possible to establish pregnancy on such a date yourself?
HCG at the 4 midwifery pregnancy week reaches the diagnostic level. Therefore, to establish the very fact of gestation, a woman can use the usual test.
Normally, the hormone concentration is 25-156 mMe / ml.
Ultrasound on the 4th obstetric week of pregnancy is conducted to confirm the fact of gestation, evaluation of the contents of the fetal egg. The use of high-resolution ultrasound equipment allows to eliminate such a violation as anembrionia, when the embryo is absent.