What is an invasive diagnostic method. Invasive methods of prenatal diagnosis. Why do patients choose the minimally invasive method

07.05.2019

Fence amniotic fluid for biochemical, hormonal, immunological, cytological and genetic studies, which make it possible to judge the condition of the fetus. Indications for amniocentesis are: isoserological incompatibility of the blood of the mother and the fetus, chronic hypoxia fetus (prolonged pregnancy, OPG-gestosis, extragenital diseases of the mother, etc.), establishing the degree of maturity of the fetus, antenatal sex diagnostics, cardiological examination for fetal malformations, microbiological examination.

Depending on the puncture site, a distinction is made between transvaginal and transabdominal amniocentesis. Transvaginal amniocentesis is recommended for gestational age up to 16-20 weeks, transabdominal - after 20 weeks. The operation is always performed under ultrasound guidance, choosing the most convenient puncture site depending on the location of the placenta and small parts of the fetus.

For transabdominal amniocentesis after treatment of the anterior abdominal wall an antiseptic solution is used to anesthetize the skin, subcutaneous tissue and subgaleal space with 0.5% novocaine solution. The study requires at least 40 ml of amniotic fluid. The puncture site on the anterior abdominal wall is treated with an antiseptic and an aseptic adhesive is applied. Transvaginal amniocentesis is performed through the anterior vaginal fornix, cervical canal, or posterior vaginal fornix. The choice of the place of insertion of the puncture needle depends on the location of the placenta. After preliminary sanitation of the vagina, the cervix is fixed with bullet forceps, shifted up or down, depending on the chosen method, and the vaginal wall is punctured at an angle to the uterine wall. When the needle enters the uterine cavity, amniotic fluid is released from its opening.

The biochemical composition of amniotic fluid is relatively constant. There are slight fluctuations in the concentration of mineral and organic substances, depending on the duration of pregnancy and the condition of the fetus. The pH value of amniotic fluid correlates with that of fetal blood obtained from the skin of the fetal head. At full-term pregnancy, the pH of the amniotic fluid is 6.98-7.23. The most informative in relation to the diagnosis of fetal hypoxia are pH values (less than 7.02), pCO 2 (over 7.33 kPA), pO2 (less than 10.66 kPA), potassium concentration (over 5.5 mmol / l), urea (7 , 5 mmol / L) and chlorides (above PO mmol / L). One of important indicators metabolism in amniotic fluid is considered creatinine, the concentration of which increases with the progression of pregnancy and at the end of it is 0.18-0.28 mmol / l. Creatinine reflects the degree of maturity of the fetal kidneys, an increase in its level in the amniotic fluid is observed with fetal malnutrition and late toxicosis pregnant women. An increase in the protein content in the amniotic fluid may indicate hemolytic disease, intrauterine fetal death, anencephaly and other fetal anomalies. The glucose level in the amniotic fluid of 15 mg / 100 ml and above "is a sign of fetal maturity, below 5 mg / 100 ml - its immaturity. With prolonged pregnancy, the glucose concentration decreases by 40% due to a decrease in the glycogen content in the placenta due to dystrophic changes.

To diagnose hemolytic disease of the fetus, the optical density of bilirubin (OPB) in the amniotic fluid is determined. The OPB value is set using a spectrophotometer at a wavelength of 450 nm. When the OPB is below 0.1, the spectrophotometric curve is assessed as physiological.

Cytological examination of amniotic fluid

In order to diagnose the degree of maturity of the fetus, cytological examination amniotic fluid. The main source of cellular composition amniotic fluid are the skin and epithelium of the urinary tract of the fetus. It includes the epithelium of the amnion, the umbilical cord and the oral cavity of the fetus. To obtain and study the sediment, amniotic fluid is centrifuged at 3000 rpm for 5 minutes, smears are fixed with a mixture of ether and alcohol, then stained using the Garras-Shore, Papanicolaou method or 0.1% Nile blue sulfate solution, which stains non-nuclear lipid-containing cells ( product sebaceous glands fetal skin) in Orange color(the so-called orange cells). The percentage of orange cells in a smear corresponds to the maturity of the fetus: up to 38 weeks of gestation, their number does not exceed 10%, over 38 weeks - reaches 50%. To assess fetal lung maturity, the concentration of phospholipids in the amniotic fluid is measured, especially the lecithin / sphingomyelin (L / C) ratio. Lecithin, saturated with phosphatidylcholine, is the main active principle of the surfactant. The values of the L / C ratio are interpreted as follows:

L / S = 2: 1 or more - mature lungs; only in 2% of cases, newborns are at risk of developing respiratory distress syndrome;
L / S = 1.5-1.9: 1 - the probability of developing respiratory distress syndrome is 50%;
L / C = less than 1.5: 1 - in 73% of cases, the development of respiratory distress syndrome is possible.

In everyday practice, a qualitative assessment of the ratio of lecithin and sphingomyelin (foam test) is used. For this purpose, add 3 ml to a test tube with 1 ml of amniotic fluid. ethyl alcohol and shake the tube for 3 minutes. The resulting ring of foam indicates the maturity of the fruit ( positive test), no foam ( negative test) indicates the immaturity of the lung tissue.

Study of amniotic fluid for the purpose of diagnosis congenital malformations development is carried out, as a rule, at a gestational age of 14-16 weeks. Fetal cells contained in the amniotic fluid and used to genetic research grown on tissue culture. The indications for amniocentesis in this case are:

the woman's age is over 35 years old (given the high risk of trisomy formation on 21 pairs of chromosomes);
Availability. chromosomal diseases in children born earlier;
suspicion of diseases linked to the X chromosome in the mother.

Complications of amniocentesis: premature effusion amniotic fluid (more often with transcervical access), injury to the vessels of the fetus, injury Bladder and the intestines of the mother, chorionamnionitis; less often - premature birth, placental abruption, fetal injury and cord injury. However, due to the widespread introduction of ultrasound guidance, complications of amniocentesis are extremely rare.

Chorionic villus sampling

Operation, the purpose of which is to obtain chorionic villus cells for karyotyping the fetus and determining chromosomal and gene abnormalities (including the determination of hereditary metabolic disorders I). Samples are taken transcervically or transabdominally from 8 to 12 weeks of gestation under supervision ultrasound scanning... Complications of chorionic villus sampling can be intrauterine infection, bleeding, spontaneous miscarriages, hematomas. To more late complications include premature birth, low weight newborns (

Cordocentesis

Cordocentesis (obtaining fetal blood samples by puncture of the umbilical vein) is performed for fetal karyotyping and immunological studies. Relative contraindications for cordocentesis are oligohydramnios, polyhydramnios, and poor fetal positioning. Potential complications (1-2%): chorionamnionitis, rupture of amniotic fluid, Rh immunization, fetal bleeding, hematoma of umbilical cord vessels, intrauterine retention growth of the fetus.

Fetal surgery

With the improvement of methods of ultrasound and invasive prenatal diagnostics, an opportunity has opened up for the development of a new direction in perinatology - fetal surgery. Some pathological conditions the fetus can be corrected before birth, which prevents the birth of children in grave condition... First intrauterine surgery- Replacement fetal blood transfusion - performed for severe hemolytic disease of the fetus by cordocentesis. However, the high frequency of intrauterine fetal death does not allow the widespread use of this method.

Another area of fetal surgery is associated with puncture and emptying of pathological fluid accumulations in the fetal cavities (hydrothorax, ascites, hydropericardium) that occur in cases of immune and non-immune dropsy of the fetus.

There have also been attempts intrauterine treatment a fetus with hydrocephalus, which was reduced to the implantation of a ventriculoamniotic shunt to reduce intracranial pressure... Despite encouraging results experimental research, the value of the clinical application of the method has not been finally established: perinatal mortality among the treated fetuses was 18%; 66% of the survivors had physical and mental development moderate to severe.

Surgical aids for reverse arterial perfusion in twins (specific pathology in multiple pregnancy, characterized by vascular communications between fetuses, which can be the cause of death of this or that twin). Reverse arterial perfusion occurs only in twins with accrete placentas. With congestive heart failure (the appearance of pericardial effusion), a puncture of the hydropericardium is performed; with polyhydramnios - therapeutic amniocentesis. In addition, it is possible to carry out ligation of communicating vessels in the umbilical cord or laser coagulation, performed under endoscopic control.

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 increased in the following cases:

mother's age 35 and older;
the birth of a child in the family with chromosomal pathology;
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);
carried over viral infections(hepatitis, rubella, toxoplasmosis and others);
irradiation of one of the spouses before conception;
presence of at least two spontaneous abortion 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 analysis blood + 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 are also taken into account, which are different in different cases... 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, heat, active infectious diseases, fibroid nodes - benign tumor muscle tissue located on the way of the needle insertion, as well as the location of the placenta on the way of the needle insertion.

How is amniocentesis and chorionic villus sampling performed?

Invasive research is usually done in outpatient... In this case, it is necessary to have results laboratory research(blood and urine tests, tests for syphilis, AIDS, hepatitis B and C, vaginal smear analysis and others - if indicated).

Invasive manipulations should be experienced specialist... The studies are carried out under local anesthesia under the guidance of an ultrasound image. A puncture is performed (puncture) of the anterior abdominal wall or access is carried out through canal B 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. The fetus is not touched during invasive studies, 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

Distinguish the following types 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 chromosome 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 through the cervix to fetal egg a catheter (a thin tube) is inserted. 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.

With 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 cells of the embryo and chorion.

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 into over time, however, it is carried out in more late dates- 12-22 weeks of pregnancy. The analysis is being prepared for several days. the main task placentocentesis - identification of 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 dates.

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 more indicators. In addition to genetic and chromosomal diseases, it is possible to determine biochemical parameters (metabolic indicators), which can be used to judge possible violations metabolism, 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 - a condition in which antibodies to the Rh-positive erythrocytes of the fetus are produced in the body of a Rh-negative mother, while the erythrocytes of the fetus are 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 for execution, since the cells obtained are few and they need to multiply, as well as certain development methods and a sufficient amount of time).

Possible complications include termination of pregnancy, leakage of amniotic fluid, infectious complications, bloody issues from the genital tract, increasing the severity 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 routine analysis blood (hormonal examination, biochemical parameters, infections, immunological conditions, etc.), and also, 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 introduction medicines, 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. For the diagnosis of 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 similar to fish scales) do a biopsy of the fetal skin. 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.

Invasive methods diagnostics (IMD) is a combined group of studies that allow you to obtain for analysis biological material of fetal origin (amniotic fluid, chorionic or placental villi, skin and blood of the fetus). This is an irreplaceable way of diagnosing many hereditary diseases, metabolic diseases, immunodeficiency states, which often do not have pronounced signs, determined by other methods.

The choice of the method is carried out jointly by a geneticist and an obstetrician-gynecologist, taking into account the gestational age and specific pathology. Always consider the possibility of termination of pregnancy and the occurrence of other complications when choosing invasive procedures. With each pregnancy, there is a so-called "baseline risk" of fetal loss, which is the sum of the woman's diseases and the effects of environmental factors, and averages 2 - 3%. This risk decreases with increasing gestational age.

Additionally When performing even the safest invasive method - amniocentesis, the probability of termination of pregnancy increases by 0.2 - 2.1% and averages 2.5 - 5.2%. The frequency of fetal loss depends on the technical equipment of the clinic, the qualifications of the doctor, the research method and general condition pregnant.

Dates of the

Exists different classifications invasive diagnostic methods.

The timing is distinguished:

IDI performed in the first trimester of pregnancy:

chorionic villi - cells of the villous part of the chorion (the outer shell of the fetus, which later transforms into the placenta) are taken for the study to determine the chromosomal set of the fetus. Samples are taken between 8 and 12 weeks of pregnancy.
- an operation by which amniotic fluid is obtained for research. The timing is the same as for a chorionic villus biopsy, but since the risk of abortion is high, it is more often performed in the second trimester.

IDI performed in the II trimester of pregnancy:

Amniocentesis – Amniotic fluid collection is usually between 17 and 22 weeks of gestation, but sometimes the test is taken up to 34 weeks.
– a method of visual inspection of the lower pole of the ovum using a thin endoscope. It can be carried out from 17 weeks of pregnancy and, if necessary, up to childbirth.
– procedure for taking placenta cells for analysis for the diagnosis of chromosomal diseases. Spend at 18 - 22 weeks.
– obtaining a fetus for a blood test for the diagnosis of hereditary blood diseases, intrauterine infection as well as the treatment of fetal hemolytic disease. Applied from 18 weeks of pregnancy.
– direct examination of the fetus to identify congenital anomalies development. Using an endoscope, it is also possible to take a piece of fetal skin for examination. Usually it is carried out at 18-24 weeks.

important In the third trimester of pregnancy, as a rule, IDI is not used due to the high risk premature birth... But sometimes, in the presence of strict indications, it is possible to carry out amnioscopy, amniocentesis and cordocentesis before childbirth.

Depending on the location of the placenta, the following types of access are distinguished :

Transabdominal - introduction of the instrument through the anterior abdominal wall;
Transcervical - penetrate into the uterine cavity through the cervical canal;
Transvaginal - pierce the anterior or posterior fornix of the vagina.

Indications for IDI:

The woman's age is over 35 years, since the frequency of spontaneous mutations increases with age, even in the absence of other risk factors;
Signs congenital pathology at ;
Deviation of the level of serum proteins in the blood of the mother;
Consanguineous marriage;
One of the spouses has a chromosomal rearrangement, hereditary disease or developmental defect;
The birth of a child with a hereditary disease or developmental disability;
Presence in anamnesis spontaneous miscarriages, stillbirths, primary amenorrhea, primary infertility in spouses;
Unfavorable influence of factors environment in the early stages of pregnancy (radiation exposure, inhalation of vaporous poisons, etc.);
Taking embryotoxic drugs in the early stages of pregnancy;
X-ray examination in the early stages;
Group or Rh incompatibility between mother and fetus.

Contraindications:

The threat of termination of pregnancy;
Inflammatory diseases of the vagina and cervix, or the skin of the abdomen (depending on the puncture site).

Possible complications after IDI:

premature rupture of amniotic fluid,
injury to the fetus,
damage to the umbilical cord,
injury to the mother's bladder and intestines,
chorioamnionitis (inflammation of the membranes).

All invasive methods of fetal diagnosis are carried out only with the consent of the pregnant woman. Before making a decision, it is necessary, as calmly as possible, to weigh the pros and cons and only then refuse to conduct the research. Very often, pregnant women do not understand that such procedures are simply not prescribed, and not revealed on time serious disease the fetus can threaten not only health, but also the life of a woman.

Invasive methods

These methods, already by their name, suggest a more serious nature of the indications for their implementation, since they themselves are more traumatic and difficult to perform and, most importantly, are not always safe for the mother and fetus.

1. Amnioscopy - this method is based on assessing the quantity and quality of amniotic fluid. Its implementation involves the introduction of a special device (endoscope) into the cervical canal, and through a visual assessment of the above data, a conclusion is made. A decrease in the amount of waters and the detection of meconium elements in them are unfavorable diagnostic signs when evaluating further state fetus. The execution technique is not too complicated. However, amnioscopy is only possible if the cervical canal can “skip” the instrument. This survey technically possible at the end of pregnancy, when the cervix is being prepared for childbirth and the partial opening of the cervical canal.

2. Amniocentesis - puncture of the amniotic cavity for the collection of amniotic fluid. Carrying out this research method is possible with the help of transabdominal access under ultrasound control of the performed manipulation. Puncture is performed in the area of the largest "pocket" of amniotic fluid, where there are no parts of the fetus and umbilical cord loops, avoiding possible trauma to the placenta. 10–20 ml of amniotic fluid is aspirated, depending on the purpose of the diagnosis. As a rule, this research method is used to diagnose congenital and hereditary diseases of the fetus, for a more accurate diagnosis of fetal lung maturity.

3. Cordocentesis - puncture of the vessels of the umbilical cord of the fetus in order to obtain its blood. This method is performed by the transabdominal route under ultrasound guidance. The manipulation is carried out in the second and third trimesters of pregnancy. This method is used for both diagnostic purposes different kinds diseases of the fetus, and for medicinal purposes.

4. Chorionic biopsy (chorionbiopsy) - obtaining chorionic villi and their further detailed study. The implementation of the method is diverse. Currently, the most commonly used aspiration transcervical or transabdominal puncture chorionic biopsy in the first trimester of pregnancy. The sampling (aspiration) of the material (chorion) for research is carried out under the control of ultrasound scanning using a special catheter or puncture needle inserted into the chorion. The main indication for this diagnostic method research is prenatal diagnosis of congenital and hereditary diseases of the fetus.

Aspiration of urine the fetus is advisable in obstructive conditions urinary system... It is performed by puncture of the urinary bladder or fetal renal pelvis under ultrasound guidance. The resulting urine is subjected to an extended biochemical study to assess functional state renal parenchyma and clarification of the need for antenatal surgical correction.

Fetal skin biopsy - a diagnostic method based on obtaining fetal skin by aspiration or forceps under ultrasound control or fetoscopic control for the prenatal diagnosis of hyperkeratosis, ichthyosis, albinism and other diseases (mainly skin and connective tissue).

Tumor tissue biopsy performed by aspiration sampling of tissue samples of a solid structure or the contents of cystic formations in order to diagnose and choose the tactics of managing this pregnancy.

Liver tissue biopsy- obtaining samples of fetal liver tissue by the same aspiration method for the diagnosis of diseases associated with a deficiency of specific liver enzymes.

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type of service: Diagnostic, service category: Histological and cytological diagnostic methods (biopsy, cytology, microscopy, etc.)

Clinics of St. Petersburg, where this service is provided for adults (7)

Clinics of St. Petersburg, where this service is provided for children (2)

Specialists providing this service (2)

Invasive prenatal diagnosis is a group of methods for obtaining samples of cells and tissues of the embryo, fetus and provisional organs (chorion, placenta) for further cytogenetic, molecular genetic, biochemical and histological studies.

Classification of methods of invasive prenatal diagnosis

The methods of invasive prenatal diagnosis include studies:

Chorion biopsy (chorionic biopsy)

Placentobiopsy (placentocentesis, placenta biopsy)

Amniocentesis

Cordocentesis

Fetal tissue biopsy

Fetoscopy

Chorion- This is the outer germinal membrane that completely surrounds the embryo. On the side facing the wall of the uterus, the chorion has numerous villi that grow into the endometrium and subsequently form the placenta. Chorion biopsy- obtaining chorionic cells, carried out at 10-14 weeks of pregnancy.

Placenta ( baby place) - an organ that develops in the uterine cavity during pregnancy, which communicates between the mother's body and the fetus. Placentobiopsy- obtaining placenta cells, carried out at 14-20 weeks of gestation.

Amnion- This is the inner embryonic membrane that surrounds the fetus. The amnion cavity is gradually filled with a large amount of effusion from the vessels, the so-called. amniotic (or amniotic) fluid that protects the embryo from mechanical damage and drying out, forming an amniotic bladder. Amniocentesis- puncture amniotic fluid with a fence small amount amniotic fluid, carried out at 15-18 weeks of gestation.

Cordocentesis- the method of obtaining the umbilical cord (cord) blood of the fetus, carried out from the 20th week of pregnancy.

Fetal tissue biopsy- the most traumatic of the listed methods, in which, under the control of ultrasound, a direct sampling of fetal tissues is carried out. The method is used to clarify the diagnosis in severe intrauterine diseases, for example, fetal skin biopsy if epidermolysis is suspected, muscle biopsy if Duchenne muscular dystrophy is suspected. Since the method is used very rarely, it is not further described in the article.

Fetoscopy- an endoscopic research method that allows you to visually examine the fetus through the inserted amniotic cavity flexible fiber optic probe. The diagnostic procedure can be supplemented with intrauterine surgical correction of some fetal malformations. Currently, the vast majority of malformations that can be seen with the help of fetoscopy are diagnosed using ultrasound, therefore the method is used very rarely and only in specialized high-tech prenatal centers, therefore, it is not further described in the article either.

The received material is further sent to laboratory diagnostics, the main types of which are classified as follows:

Cytogenetic analysis (karyotyping)

Molecular genetic analysis

Biochemical research

Histological examination

Cytogenetic analysis allows you to determine the presence of additional or missing chromosomes in the chromosome set of fetal cells. Molecular genetic analysis allows you to identify the presence of defects within chromosomes, that is, the presence of gene mutations that cause certain diseases. Biochemical research allow you to clarify the severity pathological changes with some intrauterine diseases (determining the degree of maturity of the fetal lungs, the degree of fetal hypoxia, determining the presence and severity of Rh-conflict, etc.). Histological examination Is a study of fetal tissue obtained by biopsy of fetal tissue.

Technique for invasive prenatal diagnosis

All the methods of prenatal diagnostics described in the article are carried out under the control of an ultrasound transducer. The technique of their implementation is the same, only two different approaches for puncture are distinguished: through a puncture on the anterior abdominal wall ( abdominal access) or through the vagina and cervix ( transcervical or vaginal access). The choice of access depends on the peculiarities of the location of the chorion, placenta and fetus in the uterus. Chorion and placentobiopsy are performed using both abdominal and transcervical access. Amniocentesis and cordocentesis are performed only by abdominal access (carrying out amniocentesis is possible transcervically, but rarely used).

With transcervical access under ultrasound control, a flexible catheter (a thin tube) is brought to the ovum through the cervix of the uterus. After contact with the chorion or placenta, a certain amount of tissue or amniotic fluid is aspirated (sucked in) into the catheter using a syringe.

With abdominal access under ultrasound guidance, a puncture site is selected on the anterior abdominal wall and a needle is inserted up to the uterine cavity. After making sure the needle is positioned correctly, attach the syringe and aspirate required amount tissue or amniotic fluid. After this, the needle is removed from the uterine cavity. After the end of the procedure, the condition of the fetus is assessed (the presence and frequency of its heartbeat).

Indications for invasive prenatal diagnosis

Invasive prenatal diagnosis is primarily used for early intrauterine diagnostics chromosomal (associated with the absence or presence of additional chromosomes in the chromosome set of fetal cells) and monogenic (associated with the presence of mutations in individual genes) diseases. In addition, it is possible to determine the sex of the fetus, paternity and Rh-conflict in the early stages.

Invasive prenatal examinations it is proposed to pass pregnant women at risk:

The age of the pregnant woman is over 35 years old

Complicated genetic history (a history of the birth of a child with a chromosomal or monogenic disease)

Complicated family history (family carriage of a chromosomal abnormality or gene mutation)

Already enough long time women from risk groups undergo a non-invasive prenatal screening, including the determination in the blood of a pregnant woman of the level of protein-A-plasma associated with pregnancy, human chorionic gonadotropin (hCG), as well as ultrasound examination of the fetus at 12-14 and 18-22 weeks of gestation. V recent times screening studies are recommended for all pregnant women. When detecting positive ultrasound and biochemical screening markers of chromosomal diseases in women who are not at risk, invasive prenatal diagnosis is also recommended.

Contraindications for invasive prenatal diagnosis

Contraindications to invasive prenatal diagnostics are relative, and even if they are present and with positive ultrasound markers, there is a need for research. Among the relative contraindications are the threat of termination of pregnancy, malformations of the uterus, active infectious diseases of a woman, pronounced inconsistency of the cervix, infectious lesions of the skin of the anterior abdominal wall, pronounced adhesions in the small pelvis, etc.

An absolute contraindication is only the active unwillingness of the pregnant woman to undergo invasive diagnostics... The decision to conduct a study is made by the family, the doctor only provides information on the degree of risk of having a child with chromosomal and monogenic diseases.

Assessment of research results

Invasive prenatal diagnosis followed by cytogenetic analysis allows detecting more than 90% of fetuses with the most common chromosomal diseases: Down syndrome (extra chromosome 21) and Edwards syndrome (extra chromosome 18). In addition, molecular genetic analysis allows detecting many monogenic diseases, in particular, diagnostics of the following diseases is available in Russia:

adrenogenital syndrome

albinism type OCA 1

Friedreich's ataxia

achondroplasia

Wilson-Konovalov disease

von Willebrand disease

Lesh-Nihan disease

Norrie's disease

Unferricht-Lunborg disease

hunter's disease

congenital contracture arachnodactyly

congenital muscular dystrophy, Fukuyama type

b- thalassemia,