Invasive prenatal diagnosis of chromosomal diseases. Prenatal diagnosis

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Currently, medicine has made great strides forward and makes it possible to assess the state of a child's health even at the stage of his intrauterine development. Such an assessment is of great importance, since the percentage of intrauterine fetal malformations and hereditary diseases does not decrease. Prenatal diagnosis of the fetus allows you to timely identify almost all deviations from the norm and take the necessary measures.

Prenatal diagnosis: what is it?

Prenatal diagnostic methods

All methods of prenatal diagnostics are divided into 2 groups. The first is minimally invasive or non-invasive prenatal diagnosis(prenatal screening), including:

• ultrasound procedure;
• research on the pedigree of the parents;
• genetic testing of spouses;
• Doppler ultrasound (assessment of blood flow in the mother-placenta-fetus system) according to indications;
• cardiotocography (performed from 32 weeks, according to indications from 28 weeks);
• blood for the content of serum markers ("fetal deformities").

The second group includes invasive methods, which involve surgical penetration into the uterine cavity:

• chorionic biopsy;
• placentocentesis;
• cordocentesis;
• amniocentesis;
• biopsy of fetal tissue.

Non-invasive prenatal diagnosis

Prenatal screening (elimination or sorting) is mandatory among all pregnant women and includes 2 main studies that reveal gross malformations and markers of fetal pathology.

Ultrasound procedure

Ultrasound examination is an absolutely safe method and should be performed during pregnancy at least 3 times and at certain times: at 10-14 weeks, at 22-24 weeks and at 32-34 weeks. Deviation from the recommended terms significantly reduces the percentage of pathology detection. So, at the first ultrasound, certain signs indicating a gross pathology did not appear until the 10th week, and after 14 weeks they had already disappeared. But even during the second ultrasound, it is not always possible to identify pathology and malformations (for example, small defects in the septa of the heart). Therefore, ultrasound is necessarily (in any case) supplemented by a blood test for fetal markers.

Ultrasound technique:

• Transabdominal examination
  It is performed using a transabdominal transducer that emits ultrasonic waves. The sensor is guided along the surface of the anterior abdominal wall, and the waves transmitted by it are reflected from the tissues of the unborn baby and processed by a computer. After that, a sonogram is formed on the monitor - an image that is described by a doctor. It is best to perform a transabdominal study in the second or third trimesters.
• Transvaginal examination
  Preferably done early in gestation. A vaginal probe placed in a condom is inserted into the vagina.

What allows you to identify ultrasound:

• localization of the embryo (uterine or ectopic pregnancy);
• number of fruits;
• gestational age in weeks;
• delayed fetal development;
• gender of the child;
• localization of the placenta (presentation, low placenta);
• the state of the placenta (heart attack, calcifications, degree of maturity);
• the amount of amniotic fluid (high or low water);
• the condition of the umbilical cord, the number of vessels in it, the umbilical cord node;
• the tone of the myometrium (hypertonicity with the threat of interruption or premature birth);
• fetal heartbeat and its nature (bradycardia, tachycardia);
• disturbed blood flow in the placental vessels;
• fetal anomalies (primarily neural tube, heart and kidney defects, liver and intestinal pathology, condition of the limbs and facial region of the skull);
• determination of early specific symptoms of Down syndrome (up to 12 weeks) - the width of the neck-collar space;
• position (longitudinal, transverse, oblique) and presentation (head, pelvic, facial) of the fetus.

In addition, ultrasound can diagnose cystic drift and anembryonia (absence of the embryo).

Biochemical screening

For biochemical screening, the venous blood of a pregnant woman is examined, taken within 15-20 weeks (optimally at 16-18). The first stage of screening - "double test" is carried out at 9-13 weeks, during these periods placental proteins PPAP-P and hCG are determined, in Russia it is rarely carried out. The second stage of biochemical screening is carried out in the second trimester of pregnancy and the content of alpha-fetoprotein (AFP), human chorionic gonadotropin (hCG) and free estriol is determined. In the Russian Federation, only the first 2 markers are being investigated.

What allows you to identify biochemical screening:

• Down syndrome or trisomy;
• anomalies in the development of the brain and spinal cord (absence of the brain - anencephaly, hernia of the brain and spinal cord);
• chromosomal abnormalities.

The advantages of biochemical screening include:

• high efficiency (detection of Down syndrome and neural tube defects reaches 70%);
• early diagnosis of fetal pathology (15 - 22 weeks), when the pregnancy can still be terminated;
• no risk to the fetus.

Among the shortcomings, it is worth noting the influence of various factors (multiple pregnancy, complications of gestation, diseases of the female genital organs, and others) on the reliability of the results. In view of this, the study of biochemical markers can show a false negative or false positive result.

In suspicious cases of deviations from the norm of biochemical markers, a higher level ultrasound is prescribed (in the perinatal center or in the regional / republican hospital) and invasive antenatal diagnostics.

Indications for invasive prenatal diagnosis

Considering the introduction into the uterine cavity during invasive methods, they are performed according to strict indications:

• the age of the woman (all mothers are over 35 years old, as the risk of chromosomal abnormalities of the fetus increases with age);
• closely related marriage;
• burdened history: early miscarriages, childbirth with a chromosomal abnormality;
• chromosomal pathology in one of the future parents;
• the need to determine paternity;
• abnormalities in the blood of serum markers;
• exposure of parents to mutagenic factors (radiation, polluted ecology, chemicals, medication, etc.);
• a history of the birth of a child with congenital malformations, mental disabilities or hereditary metabolic diseases (phenylketonuria);
• deviations from normal indicators of biochemical markers;
• ultrasound signs of fetal abnormalities.

Invasive Prenatal Diagnostic Techniques

• Transcervical method
  Suction of a small amount of chorionic tissue with a syringe through a cervical catheter (installed in the cervical canal).
• Transabdominal way
  A puncture of the uterus is performed through the anterior abdominal wall with a syringe with a long needle and the chorionic tissue is taken.

Chorion biopsy is performed under ultrasound guidance. It is usually performed under local anesthesia. The analysis results are ready in 3 - 4 days. The advantages of the method include its speed of obtaining results, which makes it possible to terminate a pregnancy at a safe time, identification of gene and chromosomal diseases, confirmation of paternity and establishment of the sex of the embryo.

Placentocentesis
The method is similar to a chorionic biopsy, the placenta cells are also taken, but at a later date (second trimester of pregnancy). It is also possible to obtain placental cells when entering the uterus through the cervical canal or by puncturing the anterior abdominal wall. Unlike chorionic biopsy, the culture of cells obtained by placentocentesis may not be indicative, which requires a repeat of the procedure.

Amniocentesis significantly increases the risk of possible complications of pregnancy due to long periods and is carried out only in a hospital setting with subsequent (at least 3 days) hospitalization.

Cordocentesis
The method consists in taking fetal blood from the umbilical cord. It is carried out at 18-24 weeks and allows you to identify not only chromosomal and genetic abnormalities, but the immunological and hormonal status of the fetus, determine the biochemical parameters of the blood, and so on. The analysis results are prepared for 4 - 5 days. Cordocentesis in terms of diagnostic efficiency is close to 100%.

Fetal tissue biopsy

It is carried out in the second trimester, under the mandatory supervision of an ultrasound scan. The study is shown to determine severe hereditary skin diseases in an unborn child - hyperkeratosis and ichthyosis. With these pathologies, the process of keratinization of the skin is disrupted, which leads to a thickening of the surface layer, and the skin looks like fish scales.

The material is taken in the same way as when receiving chorionic or placental tissue. A special long needle, inserted into the uterine cavity, is equipped with forceps, which grasp and separate a small piece of skin. After the material is sent to the study, which includes three types:

• Cytogenetic research
  Allows you to determine the number of chromosomes, the presence of additional or lack of chromosomes. For example, in Down syndrome, an additional 21 chromosome is detected, in Klinefelter's syndrome, in a pair of sex chromosomes in a male fetus, extra X or Y chromosomes, in Turner syndrome, a girl has a lack of an X chromosome.
• Molecular genetic research
  This method allows you to identify intrachromosomal defects, that is, gene mutations that result in the development of some diseases: hemophilia, phenylketonuria, Duchenne muscular dystrophy and cystic fibrosis.
• Biochemical research
  Allows you to assess the maturity of the lungs and determine its degree, diagnose fetal hypoxia (metabolic acidosis), identify Rh-conflict and its severity.

Disadvantages of invasive diagnostics

Despite all the advantages and high information content of invasive prenatal diagnostic methods, they also have a number of negative aspects:

• the threat of termination of pregnancy (for prevention, antispasmodics are prescribed before and after the procedure, as well as hospitalization, the duration of which depends on the method used);
• abortion;
• the risk of intrauterine infection of the fetus;
• the risk of increasing the severity of Rh-conflict;
• the risk of prenatal effusion during amniocentesis;
• the risk of bleeding in a woman;
• the risk of placental abruption.

Contraindications to invasive diagnostics

Invasive prenatal diagnosis is not indicated for the following woman's conditions:

• the threat of termination of pregnancy;
• bleeding from the genital tract;
• placental abruption;
• severe adhesions of the small pelvis;
• isthmic-cervical insufficiency;
• abnormalities in the development of the uterus;
• pustular lesions of the skin of the abdomen;
• infectious diseases of the mother;
• inflammation of the cervix and vagina;
• fibroid nodes of large sizes.

Also, a contraindication is the woman's categorical refusal to undergo invasive prenatal diagnostics.

Antenatal prenatal diagnosis of intrauterine development of the fetus is carried out in order to clarify and prevent possible deviations and is invasive and non-invasive.

Double and triple tests, when the health of the fetus is determined, as well as the most widespread non-invasive methods. For invasive diagnostics, indications are needed, since this method is considered dangerous. For medical purposes, the study is free of charge. If doctors have no suspicions of developing serious illnesses, but the expectant mother wants to be extra safe, she can voluntarily undergo this procedure on a paid basis.

There are these types of invasive prenatal examination:

• chorionic biopsy, which allows to determine genetic abnormalities up to 14 weeks with an accuracy of 99%;
• placentogenesis, which is carried out if the pregnant woman missed the timing of the biopsy;
• amniocentesis, or a study of the fetal bladder, containing particles of the baby's epithelium and his vellus hair, is carried out for up to 19 weeks and has an accuracy of 99.4%;
• cordocentesis, which allows you to determine possible pathologies by examining the blood of the baby himself with an accuracy of almost 100%.

Prenatal diagnosis of hereditary diseases

Prenatal examination of the fetus is carried out in the following cases:

1. detection of structural rearrangements of chromosomes (translocations) in one of the parents;
2. if the parents have a dominant hereditary disease;
3. if there are children in the family with a recessive hereditary disease, which indicates the heterozygosity of the parents;
4. when the mother is over 35 years old, which progressively increases the likelihood of giving birth to offspring with hereditary pathology;
5. with habitual miscarriages, causing suspicion of incompatibility between the mother and the fetus for erythrocyte antigens;
6. if there are children with congenital malformations in the family.

Since many methods of prenatal examination of the fetus are not completely harmless, and in addition, they are laborious and expensive, the indications for such an examination must be justified.

Chorionic biopsy

This is an invasive method of prenatal (antenatal) diagnosis. The essence of the method is as follows: under the control of ultrasound scanning, a thin tube (catheter) is inserted into the cervical canal of a pregnant woman. The doctor gently pushes the tube towards the ovum. The movement of the tube is monitored on the screen of the ultrasound machine. After the end of the catheter touches the chorion (this is the name of the special villi at the end of the umbilical cord, which connect it to the wall of the uterus), a very small amount of chorionic tissue is sucked into it with a syringe. It is this tissue (and not the tissue of the embryo itself) that is investigated in the laboratory by different methods.

There is another way to collect the chorion: in this case, a tissue sample is sucked into a syringe through a long needle inserted into the uterine cavity through the woman's abdominal wall. Naturally, also under the control of an ultrasound apparatus.

Chorionic biopsy makes it possible to determine the presence of Down syndrome and others in the fetus. The results of prenatal diagnostics are obtained within 3-4 days after taking the material. In the presence of a molecular genetic laboratory, it is possible to diagnose genetic diseases. Along the way, you can determine the sex of the fetus. The procedure takes a little time and is performed on an outpatient basis (i.e. without hospitalization of the woman).

Chorionic biopsy is performed at 10 to 11 weeks of gestation. It was during this period that the sufficient effectiveness and safety of the method was noted. In general, it must be said that complications are possible after this procedure of prenatal diagnosis.

• The risk of miscarriage (from 2 to 7% according to materials from different clinics)
• Risk of fetal infection (low)
• Woman's risk of bleeding (low)

Therefore, a chorionic biopsy is prescribed only if the risk of severe illness in the fetus is comparable to the risk of miscarriage after prenatal diagnosis. And of course, one should not resort to this study only for the sake of determining the sex of the fetus. In addition, accidental damage to the fetal bladder, an adverse effect during Rh-conflict between the mother and the fetus, prolonged exposure to ultrasound on the fetus, some abnormalities in the development of the fetus are possible. Sometimes, due to a number of technical reasons, it is not possible to analyze tissue samples. Summarizing, we can say that, in general, the risk of the above complications is low (no more than 2%). But this risk still exists, and you need to know about it.

The main advantage of chorionic biopsy is that the diagnosis of a severe disabling disease in the fetus can be made before the 12th week of pregnancy. At this time, the termination of pregnancy occurs with fewer complications for the woman, moreover, the stress load on family members decreases.

The direction for prenatal diagnosis by chorionic biopsy is most often given by a geneticist. Considering that before the procedure, it is necessary to undergo some examination (blood tests, smears, etc.), it is better to contact a medical genetic consultation as early as possible.

Placentogenesis

Another invasive prenatal diagnosis. The technique of their implementation is universal: puncture with a needle in the anterior abdominal wall of a woman and, under the control of an ultrasound apparatus, taking a piece of the placenta (with placentocentesis) or fetal umbilical cord blood (with cordocentesis).

Placentocentesis is usually performed in the second trimester of pregnancy, as is amniocentesis. Cordocentesis is often performed after 20 weeks of gestation. Both procedures have proven to be fairly safe for women and fetuses. Studies are performed under general anesthesia, on an outpatient basis or with short-term hospitalization.

Complications after prenatal diagnosis by methods are very rare. This is an essential advantage of these methods. The disadvantage is the long gestation period during which these studies are carried out. In the case of confirmation of the diagnosis of gross pathology, termination of pregnancy during this period requires lengthy hospitalization and is fraught with complications.

The indications for these studies of prenatal diagnosis are usually established by a geneticist in the course of medical genetic counseling.

Amniocentesis

It is also an invasive method for prenatal diagnosis. When carrying out amniocentesis under the control of an ultrasound machine (so as not to touch the fetus), a needle with a syringe is inserted into the uterine cavity (by puncturing the woman's abdominal wall). Amniotic fluid is drawn into the syringe through the needle.

In the laboratory, you can examine both the liquid itself (its chemical composition) and the fetal cells, which usually float in it. In the amniotic fluid there are desquamated cells of the fetal skin, epithelial cells from the urinary tract, etc. Therefore, the possibilities of amniocentesis are somewhat greater than that of a chorionic biopsy. In addition to prenatal diagnosis of chromosomal and gene diseases, it is also possible:

• determination of the degree of maturity of the lungs of the fetus
• determination of oxygen starvation of the fetus
• determination of the severity of the Rh-conflict between mother and fetus
• more effective diagnosis of hereditary metabolic diseases
• diagnostics of malformations (for example, defects in the closure of the neural tube)

However, there are also disadvantages:

This method of prenatal diagnosis is rather "capricious". Since there are very few fetal cells in the collected sample, it is necessary to give them the opportunity to multiply in vitro. This requires special nutrient media, temperature, reagents, and sophisticated equipment. Well, time, of course. In particular, sufficient cell growth may require 2 to 6 weeks of culture under special conditions. Therefore, the results of the study are not obtained soon, on average - by 20 - 22 weeks. If the diagnosis is confirmed, then the termination of pregnancy at this time is accompanied by a greater number of complications than, for example, at the 12th week. Stronger and moral trauma to family members.

The risk of losing a fetus after an amniocentesis is slightly less than that with a chorionic biopsy. This risk is only 0.5-1% higher than in pregnant women who did not undergo amniocentesis at all. An undesirable moment is prolonged exposure to ultrasound on the fetus. There is a slight increase in the risk of having a small baby and a very low (less than 1%) risk of respiratory disorders in a newborn.

Amniocentesis is usually performed between 15 and 16 weeks of gestation. The indications for its implementation are usually established by a geneticist in the course of medical genetic counseling.

Cordocentesis

The method refers to invasive prenatal diagnostics, which are, to a certain extent, surgical intervention. It consists in the introduction of a special needle into the uterine cavity in order to collect villi from the placenta, amniotic fluid or umbilical cord blood for further various analyzes. The need for invasive prenatal or, so-called, prenatal diagnosis is due to the ability to prevent the birth of children with various congenital or hereditary diseases.

The diagnostic capabilities of cordocentesis are somewhat greater than placentocentesis. Both methods make it possible to diagnose Down syndrome and other diseases associated with changes in the number and quality of chromosomes, and in the presence of a molecular genetic laboratory, many gene diseases.

Reliability of prenatal diagnostic results

The results of prenatal screening are distinguished by a high level of reliability and reliability. They can both refute fears of the presence of pathology, and prepare parents for the birth of a sick child.

Diagnostic procedures should be carried out in accordance with the main ethical principles:

1. Availability. All women who have a medical condition for this should undergo research. Lack of finance should not be an obstacle to the procedure.
2. Voluntariness. Doctors are obliged to explain to a pregnant woman and her husband the need for examination and the degree of risk of having a sick child. However, all appointments are advisory in nature, the final decision on the need to go through them is made by the spouses.
3. Doctors are required to provide the family with complete information about the condition of the fetus. Parents should also have a complete understanding of the nature of the disease of their unborn child, the characteristics of its development, methods of treatment and further prognosis.
4. Prenatal diagnostic procedures are carried out primarily for women who have medical indicators for this. Many impressionable women with increased levels of anxiety, who are not at risk, can also take these studies, but with full knowledge of their possible consequences.
5. The decision to terminate a pregnancy can be made exclusively by the woman herself and her family members.
6. If the family decides not to terminate the pregnancy, the doctor must familiarize the parents with the peculiarities of caring for the unborn child and mentally prepare the spouses for their future life with the baby.

It is important to remember that the decision on the need for diagnostic procedures is made jointly by an obstetrician-gynecologist, geneticist, neonatologist, pediatric surgeon, taking into account the wishes of the parents themselves.

These methods are more dangerous in terms of possible complications and more laborious to carry out, so the doctor prescribes them only for severe indications.

Invasive prenatal diagnosis 1 is divided into several types. Its task is to obtain a sample of tissue belonging to the fetus.

Who is being prescribed invasive diagnostics?

The risk of developing chromosomal and genetic diseases is increased in the following cases:

• mother's age 35 and older;
• the birth of a child with a chromosomal pathology in the family;
• identification of carriers of a familial chromosomal abnormality;
• monogenic diseases that were previously identified in the family and in close relatives;
• if, before pregnancy or at its early stage, the woman took a number of pharmacological drugs (antineoplastic and others);
• transferred viral infections (hepatitis, rubella, toxoplasmosis and others);
• irradiation of one of the spouses before conception;
• the presence of at least two spontaneous abortions in early pregnancy in the past.

These women, as well as all pregnant women, undergo non-invasive prenatal diagnostics. These are screening biochemical tests: double - at 11-13 weeks (biochemical blood test + ultrasound) and triple, as well as quadruple (with inhibin A) tests at 16-18 weeks. If the results of screening studies are alarming and the woman is at risk, the doctor determines the need for invasive procedures.

If a woman is not included in the risk group, but the results of tests and ultrasound were questionable, then she is also prescribed one of the methods of invasive diagnostics.

The decision to conduct a study is made by the family based on the information provided by the doctor. The doctor recommends a study only if the risk of serious illness in the fetus outweighs the risk of complications from invasive diagnostics. In this case, the "prices" of risks, which are different in different cases, are also taken into account. For example, a 7% risk for a woman with three children and the same risk for a woman who has no children (this pregnancy is the first after 10 years of infertility or previous pregnancies ended in miscarriages) will be assessed differently.

Contraindications to amniocentesis, chorionic villus sampling

Contraindications for conducting invasive studies are relative, that is, even if there are contraindications, it may be possible and necessary to conduct a study. So, among the contraindications is the threat of termination of pregnancy, but it is known that such a threat often arises in the presence of certain malformations of the fetus, and the study is necessary to determine the further tactics of pregnancy, and to preserve the pregnancy, the study is carried out against the background of appropriate therapy.

Contraindications may also be uterine malformations, high fever, active infectious diseases, nodes of fibroids - a benign tumor of muscle tissue located on the way of needle insertion, as well as the location of the placenta on the way of needle insertion.

How is amniocentesis and chorionic villus sampling performed?

Invasive research is usually done on an outpatient basis. In this case, it is necessary to have the results of laboratory tests (blood and urine tests, tests for syphilis, AIDS, hepatitis B and C, vaginal smear analysis, and others - according to indications).

An experienced specialist should carry out invasive manipulations. The studies are carried out under local anesthesia under the control of an ultrasound image. A puncture is performed (puncture) of the anterior abdominal wall or access is carried out through the B channel of the cervix: the choice depends on the place of attachment of the placenta in the uterus. Further, without touching the fetus, material is taken for research - particles of chorionic or placental villi, amniotic fluid or blood from the umbilical vein. During invasive studies, the fetus is not touched, unless the purpose of the study is a biopsy of the fetal tissue! Further, the pregnant woman for some time (4-5 hours) remains under the supervision of specialists. To prevent possible complications, a woman may be prescribed special medications. If during the observation certain complications are noted: there is a threat of termination of pregnancy, placental abruption, etc. - then the woman is hospitalized in a hospital and treated for complications.

Types of invasive diagnostics

There are the following types of invasive prenatal diagnosis:

• chorionic biopsy (chorionic villus sampling);
• placenthesis;
• amniocentesis;
• cordocentesis;
• biopsy of fetal tissue.

Chorionic villus sampling

It allows you to carry out studies of the chromosomal set of the fetus (for example, diagnostics of Down syndrome, Edwards, Patau) and gene mutations. The first method of conducting the study involves vaginal access: under the control of ultrasound, a catheter (a thin tube) is inserted through the cervix to the ovum. After contact with the chorion, a certain amount of chorionic tissue is absorbed with the help of it. The second method of sampling chorionic tissue - abdominal - with a syringe through the anterior abdominal wall. Such a study is also carried out under the supervision of an ultrasound scan. Chorionic villus sampling is done between 11 and 12 weeks of gestation.

The result of the analysis is known 3-4 days after taking the material. Since the study is carried out up to 12 weeks of pregnancy, if necessary, termination of pregnancy is also carried out up to 12 weeks, which is safest for the woman's body.

When conducting a chorionic biopsy, there is a risk of false-positive or false-negative results, which is explained by the phenomenon of "placental mosaicism" - the non-identity of the genome of the embryonic and chorionic cells.

There is also a risk of miscarriage, a risk of bleeding in a woman, a risk of infection of the fetus, as well as a risk of an unfavorable course of pregnancy in Rh-conflict. With Rh-conflict in the body of the Rh-negative mother, antibodies are produced that destroy the erythrocytes of the fetus. Chorionic biopsy can stimulate the production of antibodies.

It should be noted that, in general, the risk of all these complications is low: it is no more than 2%.

Placentocentesis

Placentocentesis(placental biopsy) is the taking of a sample of particles of the placenta containing fetal cells, and therefore all of its chromosomal genetic material, for examination. Placentocentesis is similar to chorionic biopsy because the placenta is what the chorion develops over time, but it is carried out at a later date - 12-22 weeks of pregnancy. The analysis is being prepared for several days. The main task of placentocentesis is to identify chromosomal and gene diseases in the fetus.

Under the supervision of an ultrasound examination, the doctor punctures the woman's anterior abdominal wall with a needle and takes a piece of the placenta for further examination. Since the study is carried out in the second trimester of pregnancy, if a pathology is detected, termination of pregnancy is more traumatic than early periods.

Placentocentesis complications can be placental abruption, the threat of termination of pregnancy, but their probability is minimal.

Amniocentesis

Amniocentesis is a method of obtaining amniotic fluid. This method makes it possible to determine a larger number of indicators. In addition to genetic and chromosomal diseases, it is possible to determine biochemical parameters (metabolic indicators), which can be used to judge possible metabolic disorders, the presence of certain diseases. For example, with the help of amniocentesis, the degree of maturity of the fetal lungs (retention of lecithin and sphingomyelin), the presence of hypoxia (oxygen starvation), Rh-conflict are determined - a condition in which antibodies to Rh-positive erythrocytes of the fetus are produced in the body of a Rh-negative mother, while erythrocytes the fetus is destroyed and the decay products of erythrocytes enter the amniotic fluid.

The study is possible from 15-16 weeks of pregnancy. Under the control of ultrasound, a syringe is inserted into the uterine cavity through the anterior abdominal wall, into which 20-30 ml of material is collected. In addition to the amniotic fluid itself, a small number of fetal cells (thickened epithelium) also enter the syringe, which are also examined.

The result of the analysis after amniocentesis is ready in 2-3 weeks (special nutrient media are required to perform, since the cells obtained are few and they need to multiply, as well as certain development techniques and a sufficient amount of time).

Possible complications include termination of pregnancy, leakage of amniotic fluid, infectious complications, spotting from the genital tract, and an aggravation of the course of the Rh-conflict. The likelihood of complications with this study is less than with a chorionic biopsy.

Cordocentesis- This is a puncture of the vessels of the umbilical cord. The material is taken by puncturing the anterior abdominal wall of the pregnant woman (under ultrasound control) and obtaining umbilical cord blood. The study is carried out after the 20th week of pregnancy. Cordocentesis allows you to perform almost all tests that can be done from a regular blood test (hormonal examination, biochemical parameters, infections, immunological conditions, etc.), and, like all other methods, helps to identify gene and chromosomal diseases. This method is used not only as a diagnostic procedure, but also as a therapeutic one - for the administration of drugs, intrauterine blood transfusion to the fetus - for example, in severe Rh-conflict.

With the help of amniocentesis and cordocentesis, infections can also be diagnosed (if infection is suspected). Termination of pregnancy can also become a complication of the procedure.

Fetal tissue biopsy as a diagnostic procedure carried out in the second trimester of pregnancy under ultrasound control. To diagnose severe hereditary skin diseases (hyperkeratosis, ichthyosis - diseases in which the process of keratinization of the skin is disturbed, the surface layer of the skin thickens, the skin becomes like fish scales), a biopsy of the fetal skin is done. The method of obtaining the material is similar to that described above, but at the end of a special needle, which is inserted into the uterine cavity, there are tweezers that allow you to get a small area of ​​the fetal skin. Further, a study is carried out, which makes it possible to clarify the presence of hereditary skin diseases. A fetal muscle biopsy is done to diagnose muscle disease.

How is the obtained material used? The tissue obtained as a result of a particular procedure is used for research. These are the main types:

Cytogenetic- using this method, the presence of additional or missing chromosomes is determined (detection of Down syndrome - an extra 21st chromosome, Klinefelter - an extra X chromosome, Turner syndrome - a lack of an X chromosome in a female fetus).

Molecular genetic- using this method, the presence of defects within the chromosomes is determined, that is, the presence of gene mutations that cause certain diseases: hemophilia, phenylketonuria, Duchenne muscular dystrophy, cystic fibrosis.

Biochemical(determining the degree of maturity of the fetal lungs, fetal hypoxia) and others (determining the presence and severity of Rh-conflict).

Subject to compliance with all the rules and regulations for invasive diagnostics, the main risk of the listed procedures is the threat of miscarriage. In quantitative terms, it is equal to 2-3%. But these indicators do not exceed the risk of the same problem in other pregnant women. Meanwhile, the result obtained is extremely important for predicting the health of an unborn child, because these diagnostic methods are the most accurate.

1 Prenatal diagnosis (pre - "before", natalis - "related to childbirth") allows you to establish the condition of the fetus before delivery.

2 Chorion is the precursor of the placenta, it is attached to the wall of the uterus.

Prenatal diagnosis is a complex of examinations. The main goal is to identify various pathologies in an infant at the stages of intrauterine development.

The most common methods of prenatal diagnostics: ultrasound, the content of various markers in the blood of a pregnant woman, chorionic biopsy, taking umbilical cord blood through the skin, amniocentesis.

What is prenatal diagnosis for?

Applying various methods of prenatal diagnostics, it is realistic to detect in the development of the fetus such disorders as Edwards syndrome, Down syndrome, disorders in the formation of the heart and other abnormalities. It is the results of prenatal diagnostics that can decide the future fate of the child. After receiving the diagnostic data, together with the doctor, the mother decides whether the baby will be born or the pregnancy will be terminated. Favorable prognosis may allow for fetal rehabilitation. Prenatal diagnosis also includes the establishment of paternity by the method of genetic examination, which is carried out in the early stages of pregnancy, as well as determination of the sex of the fetus. All these services in the capital are provided by the Center for Prenatal Diagnostics on Prospekt Mira, headed by Professor M.V. Medvedev. Here you can undergo a comprehensive prenatal examination, including ultrasound. The Center uses modern 3D and 4D technologies.

Prenatal diagnostic methods

Modern prenatal diagnostics uses a variety of methods and technologies. Their degree, as well as the level of their capabilities, is varied. In general, prenatal diagnosis is divided into two large groups: invasive prenatal diagnosis and non-invasive.

Non-invasive, or as they are also called, minimally invasive, methods do not involve surgical interventions and injury to the fetus and mother. Such procedures are recommended for all pregnant women, they are not at all dangerous. Routine ultrasound examinations must be completed. Invasive methods involve invasion (intervention) into the body of the pregnant woman, into the uterine cavity. The methods are not completely safe, therefore, the doctor prescribes them in extreme cases, when there is a question of maintaining the health of the unborn child.

Non-invasive methods include ultrasound or prenatal screening, which allows you to monitor the dynamics of the development of the fetus. Prenatal diagnosis of the fetus by the serum factors of the mother's blood is also considered non-invasive.

Ultrasound is the most common procedure, it has no harmful effects on the woman and the fetus itself. Should all mothers-to-be have this study? It is a moot point, maybe it is not required in every case. An ultrasound scan is prescribed by a doctor for many reasons. In the first trimester, you can determine the number of pregnancies, whether the fetus itself is alive, what is the exact date. In the fourth month, ultrasound can already show the rough location of the placenta, the amount of amniotic fluid. After 20 weeks, it is possible to determine the sex of the unborn child. Allows an ultrasound scan to identify various anomalies if the analysis showed a high alpha-fetoprotein in a pregnant woman, as well as if there are any malformations in the family history. It is worth noting that not a single ultrasound result can guarantee one hundred percent of the birth of a healthy fetus.

How is ultrasound performed?

Prenatal prenatal diagnosis in the form of ultrasound is recommended for all pregnant women for the following periods:

• 11-13 weeks of pregnancy;
• 25-35 weeks of pregnancy.

Provides diagnostics of the state of the mother's body, as well as the development of the fetus. The doctor places the transducer or sensor on the surface of the pregnant woman's abdomen, and sound waves invade. These waves are captured by the sensor, and he transfers them to the monitor screen. In early pregnancy, the transvaginal method is sometimes used. In this case, the sensor is inserted into the vagina. What deviations can be detected by ultrasound screening?
... Congenital defects of the liver, kidneys, heart, intestines and others.
... Up to 12 weeks, signs of the development of Down syndrome.
The development of the pregnancy itself:
... Ectopic or uterine.
... The number of fetuses in the uterus.
... Gestational age.
... Head or breech presentation of the fetus.
... Development lag in terms of timing.
... The nature of the heartbeat.
... The gender of the child.
... Location and condition of the placenta.
... Blood flow in the vessels.
... Uterine tone.

So, ultrasound examination makes it possible to identify any abnormalities. For example, hypertonicity of the uterus can lead to a threat of miscarriage. Having discovered this anomaly, you can take timely measures to preserve the pregnancy.

Blood screening

Blood serum taken from a woman is tested for the content of various substances in it:
... AFP (alpha-fetoprotein).
... NE (unconjugated estriol).
... HCG (chorionic gonadotropin).
This method of prenatal screening has a fairly high degree of accuracy. But there are times when the test shows either a false positive or a false negative result. Then the doctor prescribes additional methods of prenatal screening, for example, ultrasound or any method of invasive diagnosis.

The Prenatal Diagnostic Center on Prospekt Mira in Moscow conducts an ultrasound scan in just 1.5 hours, and also provides prenatal consultation. In addition to the first trimester screening, it is possible to undergo a second trimester biochemical screening along with counseling and ultrasound examinations.

Prenatal diagnosis of hereditary diseases uses the method of determining the level of alpha-fetoprotein in the blood. This screening test allows you to identify the likelihood of having a baby with such pathologies as anencephaly, spina bifida and others. Also, a high level of alpha-fetoprotein may indicate the development of several fetuses, the wrong timing, the possibility of miscarriage, and even a frozen pregnancy. The analysis gives the most accurate results if it is done at the 16-18th week of pregnancy. Results before week 14 or after week 21 are often erroneous. Sometimes a second blood donation is prescribed. With a high rate, the doctor prescribes an ultrasound scan, this allows more reliable confirmation of the fetal disease. If the ultrasound does not determine the cause of the high content of alpha-fetoprotein, then amniocentesis is prescribed. This study more accurately identifies altered AFP. If the level of alpha-fetoprotein in the patient's blood is elevated, complications may occur during pregnancy, for example, developmental delay, possibly fetal death, or placental abruption. Low alpha-fetoprotein in combination with high hCG and low estriol indicates the possibility of Down syndrome. The doctor takes into account all indicators: the age of the woman, the content of hormones. If required, additional prenatal research methods are prescribed.

HCG

Human or (hCG) during early pregnancy allows you to assess the most important indicators. The advantage of this analysis is the early timing of the determination, when even an ultrasound scan is not informative. After fertilization of the egg, hCG begins to be produced already on the 6-8th day.
HCG as a glycoprotein is composed of alpha and beta subunits. Alpha is identical with pituitary hormones (FSH, TSH, LH); and beta is unique. That is why the beta-subunit test (beta-hCG) is used to obtain an accurate result. In express diagnostics, test strips are used, where a less specific hCG test is used (for urine). In the blood, beta-hCG accurately diagnoses pregnancy as early as 2 weeks from fertilization. The concentration for the diagnosis of hCG in the urine matures 1-2 days later than in the blood. In the urine, the level of hCG is 2 times less.

Factors affecting hCG

When determining hCG during early pregnancy, you should take into account some factors that affect the result of the analysis.
Increased hCG during pregnancy:
... Inconsistency between the estimated and real time.
... Multiple pregnancy (the increase in the result is proportional to the number of fetuses).
... Early toxicosis.
... Gestosis.
... Serious malformations.
... Reception of gestagens.
... Diabetes.
A decrease in the level of hCG is a mismatch of the term, an extremely slow increase in the concentration of hCG by more than 50% of the norm:
... Inconsistency between the estimated and real terms (more often due to an irregular cycle).
... The threat of miscarriage (the level is reduced by more than 50%).
... Frozen pregnancy.
... Overburdening.
... Ectopic pregnancy.
... Chronic placental insufficiency.
... Fetal death in 2-3 trimester.

Invasive methods

If the doctor decides that invasive prenatal diagnosis should be used to identify hereditary diseases, developmental disorders, one of the following procedures can be used:
... Cordocentesis.
... Chorionic biopsy (study of the composition of the cells from which the placenta is formed).
... Amniocentesis (study of amniotic fluid).
... Placentocentesis (negative consequences are revealed after previous infections).

The advantage of invasive methods is speed and one hundred percent guarantee of the result. Used in early pregnancy. So, if there is any suspicion of abnormalities in the development of the fetus, prenatal diagnosis of hereditary diseases allows us to draw accurate conclusions. Parents and the doctor can make a decision in time: keep the fetus or terminate the pregnancy. If the parents, despite the pathology, still decide to leave the child, doctors have time to properly manage and correct the pregnancy and even treat the fetus in the womb. If the decision to terminate the pregnancy is made, then in the early stages, when deviations are detected, physically and mentally this procedure is much easier to tolerate.

Chorionic biopsy

It involves the analysis of a microscopic particle of the villous chorion - the cells of the future placenta. This particle is identical to the genes of the fetus, which allows you to characterize the chromosomal composition, to determine the genetic health of the baby. The analysis is carried out if there is a suspicion of diseases associated with chromosomal errors during conception (Edwards syndrome, Down's syndrome, Patau, etc.) or if there is a risk of developing incurable diseases of cystic fibrosis, sickle cell anemia, and Hentigton's chorea. The result of a chorionic biopsy reveals 3800 diseases of the unborn child. But such a defect as a defect in the development of the neural tube cannot be detected by this method. This pathology is found only during amniocentesis or cordocentesis procedures.
At the time of the analysis, the thickness of the chorion should be at least 1 cm, which corresponds to 7-8 weeks of pregnancy. Recently, the procedure is carried out at 10-12 weeks, it is safer for the fetus. But no later than the 13th week.

Carrying out the procedure

The method of puncture (transcervical or transabdominal) is chosen by surgeons. It depends on where the chorion is located relative to the walls of the uterus. In any case, the biopsy is performed under ultrasound control.

The woman is lying on her back. The selected puncture site is necessarily anesthetized with local exposure. The puncture of the abdominal wall, the wall of the myometrium is made in such a way that the needle goes parallel to the chorionic sheath. The ultrasound monitors the movement of the needle. The chorionic villus tissue is taken with a syringe, the needle is removed. With the transcervical method, the woman is placed on a chair as in a normal examination. No pronounced painful sensations are felt. The cervix and vaginal walls are fixed with special forceps. Access is provided by a catheter, when it reaches the chorionic tissue, a syringe is attached and material is taken for analysis.

Amniocentesis

Methods of prenatal diagnostics include the most common method for determining pathologies of fetal development - amniocentesis. It is recommended to carry it out at 15-17 weeks. During the procedure, the condition of the fetus is monitored by ultrasound. The doctor, through the abdominal wall, inserts a needle into the amniotic fluid, aspirates a certain amount for analysis, and the needle is removed. Results are being prepared for 1-3 weeks. Amniocentesis is of little danger to the development of pregnancy. In 1-2% of women, fluid leakage can be observed, it stops without treatment. Spontaneous abortion can occur in only 0.5% of cases. The needle does not damage the fetus; the procedure can be carried out even with multiple pregnancies.

Genetic methods

The pillbox test is the latest safe genetic method for fetal examination, it can detect the syndrome of Patau, Edwards, Down, Shereshevsky-Turner, Klinefelter. The test is carried out on the basis of data obtained from the mother's blood. The principle is that with the natural death of a certain number of placental cells, 5% of the fetal DNA enters the mother's blood. This makes it possible to diagnose major trisomies (DOT test).

How is the procedure carried out? Taken from a pregnant woman, fetal DNA is isolated. The result is issued within ten days. The test is carried out at any stage of pregnancy, starting from 10 weeks. The reliability of information is 99.7%.