Regulations 

Critical periods of fetal development and their characteristics. Time to be careful (critical periods of pregnancy). Growth and maturation of the fetus

Certain periods of intrauterine development are known when the embryo is especially sensitive to damaging agents - critical or sensitive periods. They are characterized by a high rate of cell reproduction and protein synthesis, including organ-specific ones (the period of highest stress is spurt); during these periods, the embryo enters a new stage of morphogenesis, they are the most dangerous for the life of the embryo. In humans, the first period falls on the first week of pregnancy - the pre-implantation or tubal period of embryogenesis; the second period - from 3 to 8 weeks - a period of great organogenesis, including the formation of the placenta. Most embryopathies result from the action of damaging factors during these critical periods of development. However, the brain, endocrine and reproductive system the fetus can be damaged at any stage of development, because. their critical periods exceed 8 weeks. The 3rd month of pregnancy is also considered a critical period, during which the formation of the placenta ends and its function is characterized by a high degree of activity. During this period, new reflexes appear in the fetus, the rudiments of the cerebral cortex are formed; bone marrow hematopoiesis is formed, leukocytes appear in the blood; metabolic processes are activated. It is proposed to single out another critical period - 20-24 weeks intrauterine life fetus. At this time, the formation of its most important functional systems.

The nature of pathological changes in the embryo is determined to a large extent by the time of exposure to damaging factors. Exposure to a pathogenic agent in the first critical period can lead to death or the occurrence of anomalies general(developmental delay, reduced fetal viability); damage inflicted during the second critical period causes morphological changes in one or another organ, combined with general developmental anomalies. In this case, the earlier the damaging agent acts, the more extensive changes occur in the embryo. The most dangerous in terms of damage are: for nervous system- 18th day of pregnancy; for the heart - 25-38 days; for limbs - 25-35 days; for the genitals - 36-180 days. It has been established that various pathogenic factors acting at the same time cause the same changes; similar influences affecting different dates give different effects. For example, irradiation of pregnant female rats with the same dose of X-rays on the 10th day of pregnancy causes anencephaly, on the 11th day - micro- and anophthalmia, on the 12th day - a giant edema of the body, on the 14th day - anomalies of the limbs.

The place of influence of the damaging factor also has a certain significance. Thus, the introduction of a pathogenic agent into the yolk sac in an experiment does not change organogenesis and its timing; while the application of the same substance to the surface of the chorionallantois or the introduction into its cavity disrupts organogenesis.

For a fetus that has successfully passed the critical periods of early embryogenesis, the most dangerous are the last weeks of intrauterine life, when there is a dissociation between a relatively rapid increase in fetal weight and the cessation of placental growth, as well as the period of initial adaptation of the body to a new external environment for it, which it encounters after birth. (perinatal period - from the 28th week of intrauterine life to the 8th day of the neonatal period).

Damaging factors act directly on the fetus, damaging the cell and its normal functioning or disrupting the uteroplacental circulation and placental function.

Along with high damage to the spine of the intrauterine organism to him and a certain ability to compensate. The earlier the damage occurred, which led in particular to a developmental delay, the more complete the compensation can be. So, if in animals (rabbits, rats) in the first half of pregnancy, a part of the preplacental vessels of the uterus is tied up, then in the next few days after this, a lag in the development of the fetus and a sharply deformed placenta are found. But after the same operation, full-term fetuses and their placenta do not differ from normal ones (N.L. Garmasheva).

developmental delay various bodies occurs unevenly and their ability to compensate is also different. So, with underdevelopment of neurons before birth, only far from complete functional rehabilitation is possible, and the consequences are manifested in severe neurological phenomena and mental retardation.

For antenatal fetal protection importance has knowledge of the critical periods of its development, when a high percentage of embryonic death and damage to individual organs and systems are observed. Under the action of damaging factors on the body of a pregnant woman, those organs and systems are the first to be affected, which at the time of exposure are in a state of increased differentiation and increased metabolism. In this regard, the rudiments of the nervous and cardiovascular systems are especially sensitive.

There are three stages prenatal development- the period of progenesis (the first 3 weeks), the period of embryogenesis (from the 3rd week to the 12th week), the period fetal development(from the 4th month to birth.

The first critical period of development is the pre-implantation stage and implantation. The pre-implantation stage begins from the moment of fertilization and continues until the introduction of the blastocyst into the decidua of the uterus. Implantation in humans occurs on average on the 7-8th day after fertilization.

The action of damaging factors during this period (radiation, overheating, hypoxia, etc.) causes the highest death of embryos.

The second critical period - the period of organogenesis and placentation - begins with the moment of vascularization of the villi, which occurs at the 3rd week and ends by the 12th-13th week of intrauterine development.

The action of damaging factors during this period causes disturbances in the formation of the brain, of cardio-vascular system and other organs.

In addition to critical periods in the early stages of pregnancy, V. I. Bodyazhina draws attention to the average terms of intrauterine development of the fetus, which can also be considered as a kind of critical period of development. In fetuses at the 18-22nd week of ontogenesis, qualitative changes in the bioelectrical activity of the brain, reflex reactions, hematopoiesis, the production of hormones, which in their nature approach the structures and processes characteristic of the body of a newborn.

In the second half of pregnancy, there is a decrease in the sensitivity of the fetus to the effects of damaging factors. This is due to the maturation and formation of the most important organs and systems - the nervous, cardiovascular, hematopoietic, etc., in connection with which the fetus acquires the ability to respond differently to the action environment.

It has been established that in the process of embryogenesis there is a multi-temporal maturation of the functional systems of the fetus, depending on their significance for the development of the organism on different stages prenatal period. First of all, the systems and organs that are necessary to ensure the viability of the fetus are laid down and differentiated. This uneven prenatal development fetus is the basis of the theory of systemogenesis developed by P.K. Anokhin. According to this theory, the various components of any vitally important functional system, depending on the complexity of their organization, are laid down at different speeds, but by the time of birth they all turn out to be mature and begin to function as a single whole. One of the basic regularities of the life of an organism is continuous development and a change in functional systems that provide him with adequate adaptation at various stages of postnatal life.

Nerve centers are grouped and begin to mature before the substrates innervated by them are formed and mature.

Individual tissues and organs are formed in different periods embryonic and fetal growth. At the same time, the tissues of the body at the moment of maximum intensity of the processes of differentiation become highly sensitive to the damaging effects of the external environment (ionizing radiation, infections, chemical agents). Periods that are characterized hypersensitivity to the impact of damaging factors are called "critical periods of embryogenesis". The probability of formation of deviations in development during critical periods is the highest. * According to WHO, the first critical period of development falls on the first 2 weeks of development - the period of blastogenesis. The response during this period is realized according to the “all or nothing” principle, that is, the embryo either dies, or, due to its increased stability and ability to recover, continues to develop normally. Morphological disorders that occur at this time are called "blastopathies". These include anembryony, which is formed as a result of early death and resorption of the embryoblast, aplasia yolk sac and others. Some researchers refer to blastopathies ectopic pregnancy and violations of the depth of implantation of the developing embryo. Most of the embryos damaged during the period of blastogenesis, as well as those formed from defective germ cells carrying mutations, are eliminated during this period by spontaneous abortions. According to the scientific literature, the frequency of termination of pregnancy at this time is about 40% of all pregnancies that have taken place. Most often, a woman does not even have time to find out about her onset and regards the episode as a delay in the menstrual cycle.

* The second critical period of intrauterine development lasts from the 20th to the 70th for after fertilization - this is the time of maximum vulnerability of the embryo. The entire embryonic period - from the moment of implantation to 12 weeks - is a very important period in human development. This is the time when the laying and formation of all vital organs takes place, the placental circle of blood circulation is formed, the embryo acquires a “human appearance”.

The fetal (fetal) period lasts from 12 weeks until birth. At this time, the maturation of the body occurs - a subtle differentiation of organs and tissues, accompanied by rapid growth fetus. Under the influence of unfavorable factors on developing organism during the embryonic period, the so-called "embryopathies" are formed, which are manifested by malformations. The same hazards that affect the fetus during the fetal period provoke the development of fetopathy, for which morphological defects are not typical. The frequency of embryopathies is quite high - spontaneous abortions in embryonic period at least 10% of registered pregnancies end.

In the first 2-3 months of intrauterine life, intensive cell division and the formation of tissues and organs occur. Thanks to the division, growth and migration of cells, each part of the body acquires a certain shape - the process of morphogenesis is carried out. Basically, the processes of morphogenesis are completed on the 8th week of development. Based on knowledge about the timing of the formation of organs, it is possible to draw conclusions about the development of congenital malformations in connection with the impact on the embryo of specific hazards. For example, the literature has accumulated a lot of data on the teratogenic effect of anticonvulsants, in particular, valproate. This drug can induce a complex congenital anomalies, including the combination of a spinal hernia with a ventricular septal defect of the heart. Such defects can be observed with valproate syndrome, however, for this it is necessary that the woman takes the drug until the 8th week of pregnancy, since by this time the closure of the interventricular septum and the formation of the spinal canal are completed.

Developmental disorders in the fetal period are called fetopathy (from the Latin "fetus" - fruit). Malformations during this period can occur only in organs that have not completed their formation (brain tissue, teeth, genitals, lungs). This period is characterized by the formation of so-called "secondary" malformations - that is, distortions in the development of normally formed organs due to inflammatory processes(for example, toxoplasmosis, viral infections) or violations of maturation, leading to the formation of dysplasia or hypoplasia of organs and tissues. The ability to respond with inflammatory processes to infectious damage in the fetus is formed after the 5th month of development. Metabolic disorders and chronic intoxication in the mother also contribute to the pathology of the fetal period, as an example, diabetic and alcoholic fetopathy can be cited. Of the violations of intrauterine development, the greatest clinical and social significance are birth defects development (VPR).

Modern science believes that at least 50% of all congenital malformations have a complex multifactorial nature, that is, they are formed under the influence of hereditary and environmental factors, while 5% of congenital malformations are induced by teratogenic effects. Teratogenic effects include any harmful effect, under the influence of which congenital malformations can form.

Several hundred teratogenic factors are known, but only a few are of practical importance in humans:

* Endocrine diseases of the mother ( diabetes);
* Physical effects (temperature or ionizing);
* Chemicals, which include certain medications (retinoids, valproic acid, thalidomide, etc.) and alcohol;
* Biological factors(infections - toxoplasmosis, rubella, etc.)

Some of these factors are capable of inducing certain teratological syndromes, well known to doctors all over the world. These syndromes may present as embryopathies or fetopathy, depending on the specific factor and the gestational age it affects.

The implementation of the teratogenic effect depends on many components, some of which are determined by the biology of the embryo. Here are the most significant components that determine the degree of damaging effect of a teratogen:

* The nature of the teratogen;
* Dose of teratogen;
* Duration of exposure;
* Age of the embryo or fetus;
* Genetic predisposition of the emerging organism;
* Genetic features of the mother's body, namely: the functioning of the system of detoxification of xenobiotics, neutralization free radicals and etc.

In development human body the most vulnerable are the 1st and 2nd critical period of ontogenesis - this is the end of the 1st beginning of the 2nd week after fertilization and 3-6 weeks of pregnancy. The impact of hazards during the 2nd period leads to the formation most VLOOKUP.

In addition to the critical ones, it is necessary to take into account the termination periods of the teratogen action - that is, the deadline for pregnancy during which an unfavorable factor can induce developmental anomalies. This period is determined by the timing of the completion of the formation of the organ and differs for various organs and tissues, for example, a gross malformation of the brain - anencephaly, can form under the influence of teratogenic influences up to the 8th week of pregnancy, while defects in the interventricular septum of the heart - up to the 10th week.

The significance of the genetic component of the developing organism can be demonstrated using the example of thalidomide syndrome and alcoholic fetopathy. Thalidomide syndrome was formed only in 20% of children whose mothers during pregnancy at the same terms took the same doses of thalidomide.

The influence of teratogenic factors is most often realized in the form of the development of multiple malformations and developmental anomalies, the formation of which depends on the dose of the damaging agent, the duration of its exposure and the gestational age at which the adverse effect occurred.

During pregnancy, there are periods that are critical for the development of the fetus. Also the highest is the threat of termination of the pregnancy itself, in other words, miscarriage. At this time, you should be extremely attentive to yourself, to the state of your health, in order to help the future baby feel comfortable in his first universe - his mother's tummy. Telling you in detail when you need to be careful and for what reasons is the main goal of our article.

« Critical periods" - what does it mean?

Pregnancy is one of the forms of coexistence of two organisms, two worlds, merging into a single whole: a woman and a child developing in her womb.

The successful course of pregnancy is ensured by the adaptation of the mother and the unborn child to each other. The thing is that the processes of this adaptation are very complex and at certain moments they function extremely intensely.

Critical periods of pregnancy, or critical periods in the development of the embryo and fetus, are those periods when their sensitivity increases, and adaptive capabilities decrease and the embryo becomes especially vulnerable.

These periods are characterized by active cellular and tissue processes and a significant increase in metabolism.

The effect of adverse environmental factors:
A) lack of oxygen (hypoxia),
B) hypothermia,
B) overheating
D) medicines
D) toxins
E) chemical products,
G) causative agents of viral and bacterial infections etc.,

depending on the stage of development of the embryo, it can be extremely dangerous and even fatal for him.

So let's highlight each trimester has its own critical periods in parallel with characteristic reasons termination of pregnancy.

I trimester (from the first to the 15th week of pregnancy).

The first critical period falls on the 2-3rd week of pregnancy, when a woman may not yet assume that development begins in her body. new life . At this time, implantation of the fetal egg occurs, i.e. its introduction into the uterine mucosa. The implantation process may be disturbed:

  • with anomalies in the structure of the uterus (infantilism, bicornuate or saddle uterus, the presence of a septum in the uterine cavity);
  • with endometrial injuries, i.e. the inner layer of the uterus as a result artificial abortions and inflammatory diseases(chronic endometritis);
  • in the presence of uterine fibroids;
  • with a scar on the uterus after caesarean section and other operations.

Another reason for abortion at the most early dates- chromosomal and genetic abnormalities embryo development. There is a kind of natural selection of future offspring.

Besides, implantation can be prevented by any failures in the activity of the maternal organism, stress, anxiety, severe exercise stress . This and how to try to prevent the threat were discussed in the article “Threat of miscarriage - what to do?” .

And yet I would like to note once again that it is in the early stages that it is most vulnerable. Jobs like lifting heavy bags, moving furniture, or washing bulky items by hand are not for you right now. Even if the problem is the lack of helpers, some things can be done after childbirth. Not too fresh curtains on the windows will obviously endure a few more months before the change. The whole point is that you now realize that you yourself must endure them for the sake of yourself and the future of the crumbs.

I promise that after his birth you will be so grateful to yourself that you did not once again take risks for the sake of maintaining perfect cleanliness and other favorite, but dangerous things!

The second critical period is 8-12 weeks of pregnancy.

During this period, the placenta begins to develop, and the main reason for interruption during these periods is hormonal disorders.

The main hormonal disorders leading to miscarriages:

  • dysfunction of the ovaries,
  • increased production of male sex hormones in the body of a woman,
  • dysfunction thyroid gland.

Often, these hormonal disorders can occur simultaneously in one woman. In case of miscarriage, we are usually talking about erased forms endocrine disorders with no clear symptoms. Outside of pregnancy, these disorders, as a rule, do not manifest themselves in any way, but during pregnancy they lead to a violation of the mechanisms that ensure its preservation.

Ovarian dysfunction may be congenital or the result of abortion, inflammatory processes, or dysfunction of other endocrine glands. - pituitary gland, adrenal glands, thyroid gland. Most often, there is a lack of progesterone - the ovarian hormone necessary to maintain pregnancy in its early stages.

A decrease in progesterone levels leads to the threat of termination of pregnancy. In some cases, both the level of progesterone and other ovarian hormones, especially estrogen, may be initially reduced. The latter, in particular, affect the growth and development of the uterus. With a lack of estrogen, there is an underdevelopment of the uterus and its mucous membrane - the endometrium. After fertilization, the fertilized egg is introduced into the endometrium. If it is not developed enough, then the process of implantation of the embryo into the uterine wall may be disturbed, which leads to miscarriage.

An increase in the production of male sex hormones in a woman's body may be the result of an increased formation of male sex hormones (androgens) both in the ovaries and in the adrenal glands. . In any case, an increase in androgen levels leads to a decrease in estrogen levels and often causes a miscarriage or leads to a non-developing (“frozen”) pregnancy in the early stages.

Pregnancy

Thyroid dysfunction is often accompanied by ovarian dysfunction.

II trimester (from 15 to 27 weeks of pregnancy).

The critical period is 18-22 weeks of pregnancy.

  1. Now the main reason for the interruption is infectious diseases sexually transmitted.

The causative agents of infections:

  • chlamydia,
  • toxoplasma,
  • ureaplasma
  • herpes viruses, etc.,

insidious in terms of the possibility of placental dysfunction, infection membranes, premature outflow of water.

Attention! I will stop here specifically to say: please do not panic if you have one of the listed diseases, also called “latent infections”. obstetric practice shows that a huge number of children are born absolutely healthy if the mother has similar problems, and in reality there is every chance of a successful pregnancy outcome. If the disease could not be treated in advance (which mainly occurs with unplanned pregnancy), can be treated now. There are drugs (including antibiotics) that are allowed during pregnancy and do not harm the fetus.

    At this time, the uterus is actively growing. And there is a danger of anomalies in the location of the placenta, for example, low attachment.

    Isthmic - cervical insufficiency.

The cervix during pregnancy serves as a kind of "constipation" that keeps the pregnancy in the uterine cavity.

Isthmic-cervical insufficiency is a pathology of the cervix, in which it is unable to perform this function. Under the influence of gravity, the fetal egg gradually descends, the cervix opens and ... the pregnancy is terminated.

To eliminate isthmic-cervical insufficiency, it is necessary to suture the cervix before the critical period. You should not be afraid at all, usually this manipulation is carried out after the surrender necessary analyzes, with anesthesia.

the health of your child is not an easy task, and even more so far from pleasant.

But the important thing is that With timely treatment, many diseases and pathologies can be treated. available means and during pregnancy. If there is a lot of housework, then during critical periods try to distribute your forces, postpone or “drop” the most dangerous activities. With excessive stress at work, a clear knowledge of modern legislation that regulates the rights of pregnant women will help.

Knowledge in our age is a serious, powerful weapon that allows you to avoid much more difficult problems if you use it in time. And may you be all right!

Elena VLADIMIROVA

What future mom should take care of yourself, is perceived as a common truth. But few people know that during pregnancy there are periods when the risk of all kinds of health troubles increases significantly. Keeping in " critical moments"Increased caution, a woman will be able to "insure" in time and avoid unnecessary problems.

Pregnancy lasts 9 calendar days or 10 obstetric months(her average duration is 280 days from the first day last menstrual period before giving birth). During this time, a complex process of transformation of a fertilized egg into a mature fetus, capable of independent existence outside the mother's womb, takes place. For 9 months, there is a rapid division of cells, the formation of organs and tissues of the fetus, the maturation of functional systems, the establishment of a connection between them, so that the newborn will be able to adapt to external environment, to live an independent life, separate from the mother's body.

It is difficult to overestimate the role of any period of intrauterine life of the fetus. But during pregnancy, there are several critical periods when the risk of it is highest. spontaneous interruption(miscarriage or premature birth), the occurrence of complications during pregnancy, anomalies in the development of the embryo and fetus. It is these terms that will be discussed.

Distinguish next periods fetal development during pregnancy:

    pre-implantation (from the moment of fertilization of the egg with sperm until the introduction of the fertilized egg into the mucosa of the uterine wall);

    implantation (attachment of a fertilized egg to the wall of the uterus);

    organogenesis and placentation (the period of formation of all organs and tissues of the fetus, as well as the placenta);

    fetal - a period of growth and development of formed organs and tissues.

Pre-implantation period

Normally, 12-14 days before the expected menstruation, ovulation occurs, that is, it has reached large sizes The egg leaves the ovary and enters the fallopian tube, where fertilization most often occurs. From this point on, pregnancy begins. A fertilized egg continues its journey through the fallopian tube for 4 days towards the uterine cavity, which is facilitated by:

    wall smooth muscle contraction fallopian tube. These contractions normally occur in a unilateral direction - towards the uterine cavity from the end of the tube facing the abdominal cavity;

    movement of the cilia of the mucous membrane, which covers the fallopian tube from the inside. The fluid in the tube begins to move, and with the flow of this fluid, the fertilized egg enters the uterus;

    relaxation of the sphincter (circular muscle) in the junction of the fallopian tube with the uterus. This sphincter is designed to prevent a fertilized egg from entering the uterine cavity prematurely, before the uterus is ready to receive a fertilized egg.

The movement of the egg through the fallopian tube occurs under the influence of the female sex hormones estrogen and progesterone. Progesterone is a pregnancy hormone that is produced in the ovary in the early stages of pregnancy (a corpus luteum forms in place of a burst follicle, which produces in in large numbers This hormone contributes to the onset and maintenance of pregnancy). If progesterone is not produced enough, the egg from the fallopian tube will enter the uterine cavity late. With increased peristalsis of the fallopian tube, the fertilized egg will enter the uterine cavity before it can penetrate the mucous membrane, as a result of which the egg may die. Since pregnancy will not take place, delays next menstruation will not be, then the pregnancy remains undiagnosed, unrecognized. The period of advancement of a fertilized egg through the fallopian tube is considered the first critical period of pregnancy (from 12-14 to 10-8 days before the next menstruation). As a result of a violation of the complex mechanisms of regulation of the work of the fallopian tube, the egg after fertilization can also be introduced into the wall of the tube (ectopic pregnancy).

Implantation period

This period also passes even before the expected menstruation, most often when the woman is still unaware of her pregnancy. Once in the uterine cavity, the embryo already consists of 16-32 cells, but it does not immediately penetrate into the uterine mucosa, and is in a free state for another two days. These two days from the moment the fertilized egg enters the uterine cavity to its attachment to the uterine wall constitute the implantation period. The place of implementation depends on a number of circumstances, but most often it is the anterior or back wall uterus.

The nutrition of the fetal egg during this period occurs due to the local dissolution of the mucous membrane of the uterine wall with the help of enzymes secreted fertilized egg. After 2 days, the fetal egg is introduced into the uterine mucosa, which contains a large amount of enzymes, glycogen, fats, trace elements, protective antibodies and other biologically active substances necessary for further growth of the embryo.

The second critical period of pregnancy is implantation, that is, the attachment of the fetal egg to the wall of the uterus. If implantation fails, then the pregnancy ends under the guise of menstruation (in fact, this is an undiagnosed miscarriage at a very short time). Since there is no delay in menstruation. the woman does not even assume that she is pregnant.

The process of implantation is greatly influenced by hormonal factors: the concentration of hormones such as progesterone, estrogens, prolactin (a pituitary hormone - a gland located in the brain). glucocorticoids (adrenal hormones), etc.

Of great importance is the preparedness of the uterine mucosa for implantation, its readiness to accept a fetal egg. After abortions, curettage, prolonged wear intrauterine device, infections, inflammatory processes, the receptor (perceiving) apparatus of the endometrium can be disrupted, that is, hormone-sensitive cells located in the uterine mucosa do not respond correctly to hormones, due to which the uterine mucosa is not sufficiently prepared for the upcoming pregnancy.

If the fetal egg is not active enough, does not release the required amount of enzymes that destroy the uterine mucosa in a timely manner, then it can penetrate the uterine wall in the lower segment or in the cervix, resulting in pregnancy or an abnormal placenta (the placenta blocks the exit from the uterus partially or completely) .

The presence of adhesions (synechia) in the uterine cavity after inflammatory processes, curettage, as well as uterine fibroids, can also interfere with normal implantation.

Each embryonic germ and the organ that develops from it has its own critical periods of sensitivity, when the action various factors selectively disrupts organogenesis. So, for the brain, the 23-28th day, the 30-42nd day, the 45th day, the fifth month of intrauterine life are critical; for the lens of the eye - 23-45 days, for the limbs - 28-56 days, for the cardiovascular system - 23-51 days of intrauterine development (in this case, the days are counted from conception)

Period of organogenesis and placentation

What should be cause for concern?

If the effect of unfavorable factors in critical deadlines led to the threat of abortion, women complain of pain in the lower abdomen, in the lower back - pulling or cramping. Pain may be accompanied by bloody discharge from the genital tract. Such symptoms should not be left without due attention, because. following them, massive bleeding may occur due to incomplete spontaneous miscarriage in which the pregnancy cannot be saved.

Very important at the first symptoms threatened miscarriage contact a gynecologist immediately necessary research, including examination on a chair, ultrasound, hormonal blood tests for female sex hormones, male sex hormones, thyroid hormones.

This period lasts from the moment of introduction of the fetal egg into the uterine mucosa until 10-12 weeks of pregnancy, when all organs and tissues of the fetus, as well as the placenta, are fully formed. placenta - children's place - connecting link between the fetus and the mother's body, with the help of which the processes of nutrition, metabolism and respiration of the fetus occur in the womb. This is a very important period of intrauterine life, because. in it time runs laying of all organs and tissues of the fetus. Already on the 7th day after the fertilization of the egg, the mother's body receives a signal of pregnancy due to the hormone - chorionic gonadotropin (CG), which is secreted by the fetal egg. CG, in turn, supports the development corpus luteum in the ovary. The corpus luteum secretes progesterone and estrogens in sufficient quantities to maintain pregnancy. On the initial stage pregnancy, before the formation of the placenta, the corpus luteum takes on the function of hormonal support for pregnancy, and if for one reason or another the corpus luteum does not work properly, then there may be a threat of miscarriage, miscarriage or non-developing pregnancy.

The entire period of organogenesis and placentation is also a critical period of intrauterine life of the fetus, because the fetus is highly sensitive to the damaging effects of the environment, especially in the first 3-6 weeks of organogenesis. This critical period in the development of pregnancy is especially important, because. under the influence of adverse environmental factors, the embryo may die or develop abnormalities.

During these periods, the influence of environmental factors on the embryo is especially dangerous, including:

    physical (ionizing radiation, mechanical influences); this can be the action of ionizing radiation, for example, in the conditions of a man-made disaster at nuclear facilities, mechanical effects in the form of vibration, and so on. in the relevant industries or at the time of sports training;

    chemical: phenols, nitric oxide, pesticides, heavy metals, etc. - these substances can also enter the body of a pregnant woman if she works in the relevant industries or during repairs in a room where a woman stays for a long time. To chemicals include nicotine, alcohol, some medications. For example, used for the treatment of cancer, etc.;

    biological (for example, herpes virus, cytomegalovirus, rubella virus, etc.).

It must be emphasized that during critical periods harmful effects lead to the most grave consequences- death of the embryo or the formation of gross malformations.

According to French researchers, if a pregnant woman encounters cytomegalovirus for the first time in her life, the pathogen disease-causing, which in adults can proceed as a banal acute respiratory disease during pregnancy (as seen from a blood test for immunoglobulins to CMV), especially in the early stages, fetal malformations may occur in 1/3 of cases. If, before pregnancy, she was already infected, the body turns on the protective mechanisms to fight the virus in time, and this probability decreases to 1%. The same can be said about the herpes simplex virus.

Of particular danger is the rubella virus when infected with it in the early stages of pregnancy. In this case, a woman is recommended interruption pregnancy, because there is a high risk of having a child with malformations such as microphthalmia - a malformation of the eyes, microcephaly - a serious malformation of the brain, deafness, congenital heart defects, etc.

From chemical compounds lead, mercury, benzene, nicotine, carbon oxides and other substances that can cause malformations are especially adversely affecting the state of the embryo.

Some drugs are especially contraindicated during pregnancy (eg anticancer antibiotics); if they were taken, early termination of pregnancy is recommended. When taking some medicines consultation with a geneticist is necessary, careful monitoring during pregnancy of the state of the embryo and fetus (ultrasound, blood test for chorionic gonadotropin, alpha-fetoprotein, estriol, which make it possible to suspect the presence of fetal malformations - the analysis is carried out at 16-20 weeks of pregnancy).

women working for chemical production, during pregnancy, it is necessary to transfer to other, less dangerous workshops. As for the effect of radiation, if it affects a woman before the implantation of the embryo (during the pre-implantation period), in 2/3 of the cases the embryo dies. During the period of organogenesis and placentation, malformations often occur or intrauterine death of the embryo or fetus occurs.

At 7-8 weeks of pregnancy, the reverse development of the corpus luteum in the ovary usually begins: figuratively speaking, the ovaries transfer the function of hormonal support for pregnancy to the chorion (future placenta), and if the chorion is not sufficiently developed, not active, then there is a threat of termination of pregnancy.

7-8 weeks is also a critical period for the development of pregnancy. Very common miscarriage, missed pregnancy, or threatened miscarriage ( bloody issues from the genital tract, pain in the lower abdomen and lower back) appear precisely at this time. If this happens, the woman needs hospitalization. The hospital uses various medications to help keep the pregnancy, if possible.

So, as we have seen, the first trimester of pregnancy almost entirely consists of critical periods, so at this time it is especially important:

    if possible, eliminate the negative impact of harmful production;

    change complex exercise with active training in the period before pregnancy, postpone classes extreme views sports for the postpartum period;

    conduct enough outdoor time;

    enough time (8-10 hours) to sleep;

    not to accept Active participation in the repair of premises;

    give up bad habits especially such as alcohol, drugs, smoking.

fertile period

From 12 weeks of pregnancy, the fetal period of intrauterine life begins, which lasts up to 40 weeks. At this time, the fetus is already fully formed, but physically immature.

Pregnancy periods of 13, 20-24 and 28 weeks are critical for patients with hyperandrogenism - high content male sex hormones - due to the beginning of the production of fetal hormones. During these periods, it is necessary to check the level of hormones and adjust the dose of drugs that are prescribed to reduce the amount of male sex hormones (DEXAMETHA3ONE, METIP-RED, etc.). At the same time, the doctor monitors the condition of the cervix, since an increase in the amount of male sex hormones can lead to its premature opening.

At 13 weeks of pregnancy, the male fetus begins to produce its own testosterone - the male sex hormone, at 20-24 weeks the production of cortisol and male sex hormones by the adrenal cortex of the fetus begins, as a result of which a woman with hyperandrogenism may have another rise in male sex hormones, which will lead to termination of pregnancy.

At 28 weeks, the fetal pituitary gland begins to synthesize a hormone that stimulates the adrenal glands. - - adrenocorticotropic hormone, resulting in increased production of male sex hormones, which can also lead to abortion. If necessary, the doctor will adjust the dose of medications at this time.

So, the action of unfavorable factors during critical periods of pregnancy can lead to the most adverse effects. Therefore, during the entire period of expectation of a child, and especially during critical periods, a woman should avoid the action of adverse factors and consult a doctor in case of any “malfunctions”. I would like to advise expectant mothers to take care of themselves, especially since pregnancy lasts only 9 months, and the health and life of your baby depends on its course.

Kriticheskie_periody_pregnancy.txt · Last changes: 2014/11/28 00:16 (external change)