The teratogenic effect of drugs causes the appearance of malformations, as well as abnormalities in the development of the child due to their use by the mother during pregnancy. Teratogenesis develops under the influence of factors acting externally on the emerging organism of the fetus, is also possible under the influence of hereditary diseases.
What is it due to?
The teratogenic effect is due to the passage of drugs or their transformation products through the barrier between the uterus and the placenta, as a result of which the formation of organs and tissues of the embryo is disturbed.
Critical periods
At different stages of pregnancy, various injuries occur, associated with the chronological formation of body structures - these are critical periods. The most dangerous in terms of the development of serious disorders are the first 2-3 months of pregnancy. It should be noted that at earlier times, under the influence of such factors, disturbances also occur in the emerging organism, however, they are incompatible with life: a miscarriage (spontaneous abortion) occurs. The critical periods for different organs are different: 23-28 days of intrauterine development are important for the brain, 23-45 days for the organ of vision, limbs form on 28-56 days and so on.
What factors cause?
The following factors cause teratogenic effects: drugs, infections (rubella, herpes, cytomegalovirus, parvovirus, syphilis, toxoplasmosis), metabolic disorders in a pregnant woman (endemic goiter, decompensated diabetes mellitus, prolonged hyperthermia, androgen-producing tumors), drugs (androgens, methotrex , enalapril, iodides, methimazole, tetracyclines, thalidomide, valproate, warfarin, busulfan), ionizing radiation (radiation therapy for cancer, therapy with radioactive iodine, adioaktivnye rainfall) and much more.
Impact Features
These factors influence with some features. The teratogenic effect is due to the dose. In addition, before exposure to any factor in the subthreshold values of defects, the fetus does not form. The teratogenic effect in different biological species and even in different representatives of the same species may be different, which is associated with individual characteristics of metabolism (absorption, distribution and excretion in the mother's body and direct penetration through the
uteroplacental barrier). However, when a mother is exposed to infection, it is not possible to determine a threshold dose.
Distribution of factors
Teratogenic factors are widely found in the environment. As a result of studies, it was found that a woman takes about 3-4 medicinal substances during pregnancy. In addition, pregnant women may come into contact with various harmful compounds at work or at home. The teratogenic effect of drugs should be established in studies: the relationship between the direct impact of the factor and the appearance of a defect with confirmation of epidemiological data must be proved. In addition, the influence of the factor must coincide with critical periods.