How does the fetus develop?
It is worth noting that in obstetrics there are 2 concepts: embryonic and obstetric term. The first is from conception, the second is the first day of menstruation. Therefore, there is a difference of 2 weeks between them (on average).
Fruit egg in 4 weeks from conception is very small, and its size does not exceed 5-7 mm in diameter. If we talk about the future baby, then it is at this time even less, only 2-3 mm.
At 4 weeks from conception, the embryo has a differentiation of future tissues. By this time, there are 3 embryonic leaves.
The outer layer - ectoderm, gives rise, first of all, to the nervous system of the future baby. The middle one is mesoderm, it takes an active part in the formation of the fetal skeleton, its tissues, and also blood.
Endoderm, in turn, being the innermost, forms directly systems of organs, separate anatomical structures. The future fetus in 4 weeks from conception already has an embryo of the cardiovascular system. As its protrudes the heart tube. Fixation of its contractions is possible with the help of an ultrasound machine at this time.
Separately it is necessary to say about such an important anatomical structure as the placenta. It is at this point that its formation begins. Recall that the final maturation is observed only by the 20th week.
How does the future mother feel?
In most cases, it is at this time that a woman finds out about her situation. A test made in such a period shows a positive result.
The woman notes the appearance of the first signs of pregnancy: irritability, sharp mood swings, dizziness, nausea in the morning.