Human development proceeds according to the genetic plan inherited from mom and dad. The implementation of hereditary inclinations occurs in close interaction with the environment in which the organism is formed. The habitat for the growing embryo is the internal environment of the mother’s body, which depends both on her health and nutrition, and on the influence of environmental factors. Moreover, the environment always has a modifying effect on the result that the implementation of an initially normal genetic program leads to.

For the convenience of doctors and scientists, the continuous process of intrauterine development is divided into periods, each of which has its own characteristics. Although there is no clear boundary between the periods, and there are discrepancies regarding their duration, knowledge of these periods is extremely important for teratology.

The first week of a new life – the preembryonic period or blastogenesis

From the moment of fertilization until implantation of the embryo into the wall of the uterus. During this period, the processes of activation of genes necessary for the synthesis of certain proteins, division and fragmentation of the zygote, spatial differentiation of the future organism, migration of cells to certain areas of the embryo, formation of germ layers and extra-embryonic parts of the embryo take place in the fertilized egg.

Embryonic period

From the moment of implantation to the 12th week – this is a very crucial period in human development – the formation and formation of all vital organs occurs, accompanied by rapid growth of the fetus.

45 days after fertilization, the embryo is called a fetus (after stage 17 of development according to Carnegie). By the 10th week, the main formation of organs is completed and from this period the tissues “ripen” and the organs increase in volume. By the end of the 3rd month, the skin loses its transparency and is gradually covered with vellus hair. By the beginning of the 4th month, the formation of the muscular system is completed, the fetus begins to move its limbs.

Maximum fetal growth occurs at 3–5 months of intrauterine development, at the 20th week the growth rate is 2,5 cm per week. Starting from the 32nd week of pregnancy, the maximum increase in body weight occurs; in the last 8 weeks of pregnancy, the weight of the fetus doubles.

Critical periods in fetal development

Tissues and organs are formed during different periods of fetal growth. At the time of these processes, the tissues of the body are sensitive to the damaging influences of the external environment. Such periods are called “critical periods of embryogenesis.” There is a high risk of developing developmental deviations during critical periods. “Embryopathies” can form – they are manifested by developmental defects.

Of the disorders of intrauterine development, congenital malformations (CDM) are of greatest importance. About 50% of all congenital malformations are formed under the influence of environmental factors and hereditary factors:

  • Physical influences
  • Endocrine diseases (diabetes mellitus)
  • Chemicals and alcohol
  • Biological factors (infections)

In our medical center on Kaluzhskaya, experienced obstetrician-gynecologists will help you in matters of monitoring your pregnancy.

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