Invasive methods of prenatal diagnosis. Invasive methods

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

Prenatal diagnosis: what is it?

Prenatal diagnostics Prenatal or prenatal diagnostics is a set of fetal studies that allows you to identify or refute intrauterine developmental anomalies, chromosomal and gene diseases of the unborn child. Prenatal diagnostics is the youngest, but successfully developing branch of reproductive medicine. After receiving the results of the study, medical and genetic counseling of the spouses is carried out and the questions are resolved: does it make sense to prolong the pregnancy, is it possible to treat a child with an identified pathology after birth or in utero, and how to prevent deviations from normal development fetus in the next pregnancy.

Prenatal diagnostic methods

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

ultrasonography;
research of the parents' pedigree;
conducting genetic research of spouses;
Ultrasound with Dopplerometry (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 (“for fetal deformities”).

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

chorionic villus biopsy;
placentocentesis;
cordocentesis;
amniocentesis;
fetal tissue biopsy.

Non-invasive prenatal diagnostics

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

Ultrasonography

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

Ultrasound technique:

Transabdominal examination
It is carried out using a transabdominal sensor that emits ultrasonic waves. The sensor is placed 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 the doctor. Transabdominal examination is best performed in the second – third trimesters.
Transvaginal examination
It is preferable to carry out in early gestation. A vaginal sensor placed in a condom is inserted into the vagina.

What does ultrasound reveal:

location 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 (previa, low placentation);
condition of the placenta (infarction, calcifications, degree of maturity);
amount of amniotic fluid (multiple or oligohydramnios);
the condition of the umbilical cord, the number of vessels in it, the umbilical cord node;
myometrial tone (hypertonicity in case of threatened miscarriage or premature birth);
fetal heartbeat and its character (bradycardia, tachycardia);
impaired blood flow in the placental vessels;
abnormalities of fetal development (primarily defects of the neural tube, heart and kidneys, pathology of the liver and intestines, condition of the limbs and facial part of the skull);
definition of early specific symptoms Down syndrome (up to 12 weeks) – width of the cervical-collar space;
position (longitudinal, transverse, oblique) and presentation (cephalic, pelvic, facial) of the fetus.

In addition, ultrasound allows you to diagnose hydatidiform mole and anembryony (absence of an embryo).

Biochemical screening

To conduct biochemical screening, the venous blood of a pregnant woman is examined, taken at 15–20 weeks (optimally at 16–18). The first stage of screening is “ double test“carried out at 9–13 weeks, during these periods placental proteins PPAP-R and hCG are determined; it is rarely performed in Russia. 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 Russian Federation Only the first 2 markers are examined.

What biochemical screening reveals:

Down syndrome or trisomy;
abnormalities in the development of the brain and spinal cord (absence of the brain - anencephaly, herniation 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 pregnancy can still be terminated;
no risk to the fetus.

Among the disadvantages, it is worth noting the influence of various factors ( multiple pregnancy, complications of gestation, diseases of the female reproductive organs and others) on the reliability of the results. Therefore, the study of biochemical markers may show a false negative or false positive result.

In suspicious cases of abnormal biochemical markers, a higher level ultrasound (in the perinatal center or in a regional/republican hospital) and invasive prenatal diagnostics are prescribed.

Invasive prenatal diagnostics Prenatal invasive diagnostics provides a 100% guarantee of results (detection of hereditary diseases, malformations and chromosomal aberrations), and is also different quick receipt research results. Also on the plus side invasive diagnostics This includes identifying pathology in early stages of pregnancy (up to 14 weeks), and parents are given a choice: either have an abortion or prolong the pregnancy. If the embryo is preserved, doctors have enough time to correct developmental defects and treat fetal diseases in utero.

Indications for invasive prenatal diagnostics

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

woman’s age (all mothers are over 35 years old, as the risk increases with age chromosomal abnormalities fetus);
consanguineous marriage;
complicated medical history: early miscarriages, birth of a child with a chromosomal abnormality;
chromosomal pathology in one of the future parents;
the need to determine paternity;
abnormalities in blood serum markers;
exposure of parents to mutagenic factors (radiation, polluted environment, chemical substances, taking medications, etc.);
history of the birth of a child with congenital malformations, deviation in mental development or hereditary metabolic diseases (phenylketonuria);
deviations from normal indicators biochemical markers;
ultrasound signs of fetal abnormalities.

Methods of invasive prenatal diagnostics

Chorionic villus biopsy
The method involves sampling and subsequent examination of chorion cells. The chorion is the embryonic membrane, which in the future will transform into the placenta. Chorionic biopsy is performed at 10–11 weeks of gestation in two ways:

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

Chorionic biopsy is performed under control ultrasound examination. Typically performed under local anesthesia. The analysis results are ready in 3–4 days. The advantages of the method include its speed in obtaining results, which makes it possible to terminate a pregnancy at a safe time, identification of gene and chromosomal diseases, confirmation of paternity and determination of the sex of the embryo.

Placentocentesis
The method is similar to chorionic villus biopsy; placental cells are also collected, but at a more advanced stage. later(second trimester of pregnancy). It is also possible to obtain placenta cells by entering the uterus through the cervical canal or by puncturing the anterior abdominal wall. Unlike chorionic villus biopsy, culturing cells obtained by placentocentesis may not be indicative, which requires repeating the procedure.

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

Amniocentesis
The method is to collect amniotic fluid by puncture of the anterior abdominal wall, uterus and amnion. The amniotic fluid is examined for the content of hormones, enzymes and amino acids on which fetal growth depends. Together with amniotic fluid, it examines desquamated epithelial cells of the fetal skin and urinary tract. The study is carried out at 16–18 weeks. The method is highly informative and its effectiveness reaches 99%. Disadvantages include the duration of the analysis (from 2 weeks to 1.5 months). Allows you to diagnose gene and chromosomal aberrations, determine the maturity of the fetal lungs, the severity of Rh conflict, some abnormalities of fetal development and the degree of intrauterine hypoxia.

Cordocentesis
The method involves taking fetal blood from the umbilical cord. It is carried out at 18 - 24 weeks and allows you to identify not only chromosomal and gene abnormalities, but the immunological and hormonal status of the fetus, determine biochemical blood parameters, etc. The analysis results are prepared within 4–5 days. Cordocentesis' diagnostic efficiency is close to 100%.

Fetal tissue biopsy

It is carried out in the second trimester, under mandatory ultrasound control. The study is indicated for determining severe hereditary skin diseases the unborn child has hyperkeratosis and ichthyosis. In these pathologies, the process of keratinization is disrupted skin, which leads to a thickening of the surface layer, and the skin looks like fish scales.

The material is collected in the same way as when obtaining chorionic or placental tissue. A special long needle inserted into the uterine cavity is equipped with tweezers, which capture and separate a small piece of skin. Afterwards, the material is sent for research, which includes three types:

Cytogenetic study
Allows you to determine the number of chromosomes, the presence of additional or lack of chromosomes. For example, with Down syndrome, an additional 21 chromosome is detected, with Klinefelter syndrome, there are extra X or Y chromosomes in a pair of sex chromosomes in a male fetus, and with Turner syndrome, there is a lack of an X chromosome in a girl.
Molecular genetic research
This method allows you to identify intrachromosomal defects, that is, gene mutations that result in the development of certain 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:

threat of miscarriage (for prevention, antispasmodics are prescribed before and after the procedure, as well as hospitalization, the duration of which depends on the method used);
abortion;
risk intrauterine infection fetus;
the risk of increasing the severity of Rh conflict;
risk of antenatal rupture of water during amniocentesis;
risk of bleeding in women;
risk of placental abruption.

Contraindications to invasive diagnostics

Invasive prenatal diagnosis is not indicated for the following conditions of a woman:

threat of miscarriage;
bleeding from the genital tract;
placental abruption;
severe adhesive disease of the pelvis;
isthmic-cervical insufficiency;
abnormalities of the uterus;
pustular lesion of the skin of the abdomen;
maternal infectious diseases;
inflammation of the cervix and vagina;
large fibroid nodes.

Also a contraindication is a woman’s categorical refusal to undergo invasive prenatal diagnostics.

Invasive diagnostic methods (IDM) are a combined group of studies that make it possible to obtain biological material of fruit origin for analysis ( amniotic fluid, chorionic villi or placenta, skin areas and fetal blood). This is an indispensable method for diagnosing many hereditary diseases, metabolic diseases, and immunodeficiency conditions, which often do not have pronounced symptoms, determined by other methods.

The choice of method is carried out jointly by a geneticist and an obstetrician-gynecologist, taking into account the duration of pregnancy and the specific pathology. When choosing invasive procedures, the possibility of termination of pregnancy and the occurrence of other complications should always be taken into account. With every pregnancy, there is a so-called “basic risk” of fetal loss, which is the sum of a woman’s diseases and exposure to environmental factors, and averages 2–3%. As pregnancy progresses, this risk decreases.

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

There are different classifications of invasive diagnostic methods.

According to the timing of the event, they are distinguished:

IMD performed in the first trimester of pregnancy:

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

IMD performed in the second trimester of pregnancy:

Amniocentesis – Amniotic fluid is usually taken at 17–22 weeks of pregnancy, but sometimes the test is carried out up to 34 weeks.
– a method of visual inspection of the lower pole of the ovum using a thin endoscope. Can be performed from 17 weeks of pregnancy and, if necessary, until birth.
– a procedure for taking placenta cells for analysis to diagnose chromosomal diseases. Conducted at 18–22 weeks.
– obtaining fetal blood for analysis to diagnose hereditary blood diseases, intrauterine infection, as well as treatment of hemolytic disease of the fetus. Used from 18 weeks of pregnancy.
– direct examination of the fetus to identify congenital malformations. Using an endoscope, it is also possible to take a piece of fetal skin for examination. Usually carried out at 18 – 24 weeks.

important IN III trimester During pregnancy, as a rule, IMD is not used due to the high risk of premature birth. But sometimes, if there are strict indications, it is possible to perform amnioscopy, amniocentesis and cordocentesis before birth.

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

Transabdominal – insertion of the instrument through the anterior abdominal wall;
Transcervical – enter the uterine cavity through the cervical canal;
Transvaginal – pierce the anterior or posterior vaginal fornix.

Indications for IMD:

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;
The presence of signs of congenital pathology in;
Deviation of the level of serum proteins in the mother’s blood;
Consanguineous marriage;
The presence of a chromosomal rearrangement, hereditary disease or developmental defect in one of the spouses;
The birth of a child with a hereditary disease or developmental defect;
A history of spontaneous miscarriages, stillbirths, primary amenorrhea, primary infertility in spouses;
Adverse effects of environmental factors in early dates pregnancy (radioactive exposure, inhalation of vaporous poisons, etc.);
Taking embryotoxic drugs in early pregnancy;
X-ray examination in the early stages;
Group or Rh incompatibility of mother and fetus.

Contraindications:

Threat of miscarriage;
Inflammatory diseases of the vagina and cervix, or abdominal skin (depending on the puncture site).

Possible complications after IMD:

premature effusion amniotic fluid,
fetal injury,
umbilical cord damage,
wound Bladder and the mother's intestines,
chorioamnionitis (inflammation of the membranes).

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

Prenatal prenatal diagnosis of intrauterine development of the fetus is carried out with the aim of identifying and preventing possible deviations and can be invasive or non-invasive.

Double and triple tests, when the health of the fetus is determined, as well as the most widely used non-invasive methods. Indications are needed for invasive diagnosis, since this method is considered dangerous. For medical purposes, the study is carried out free of charge. If doctors do not suspect development serious illnesses, however future mom wants to be extra safe, she can voluntarily undergo this procedure on a paid basis.

There are the following types of invasive prenatal research:

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

Prenatal diagnosis of hereditary diseases

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

detection of structural chromosome rearrangements (translocations) in one of the parents;
if the parents have a dominant hereditary disease;
if there are children in the family with a recessive hereditary disease, which indicates heterozygosity of the parents;
when the mother is over 35 years old, which progressively increases the likelihood of her having offspring with a hereditary pathology;
with recurrent miscarriages that raise suspicion of incompatibility between mother and fetus based on erythrocyte antigens;
if there are children in the family with congenital malformations.

Since many methods of prenatal examination of the fetus are not absolutely harmless, and in addition, they are labor-intensive and expensive, the indications for such examination must be justified.

Chorionic villus 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 advances the tube towards the fertilized egg. The movement of the handset is tracked on the screen ultrasound machine. After the end of the catheter comes into contact with the chorion (the so-called special villi at the end of the umbilical cord that connect it to the wall of the uterus), very a small amount of chorionic tissue. It is this tissue (and not the tissue of the embryo itself) that is studied in the laboratory using different methods.

There is another way to collect 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 machine.

Chorionic villus 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. If a molecular genetic laboratory is available, it is possible to diagnose genetic diseases. At the same time, the sex of the fetus can be determined. The procedure takes little time and is performed on an outpatient basis (i.e., without hospitalization of the woman).

A chorionic villus biopsy is performed at 10–11 weeks of pregnancy. It was during this period that the method was sufficiently effective and safe. In general, it must be said that complications are possible after this prenatal diagnostic procedure.

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

Therefore, chorionic villus sampling is prescribed only when the risk of severe disease in the fetus is comparable to the risk of miscarriage after prenatal diagnosis. And of course, you should not resort to this study just to determine the sex of the fetus. In addition, accidental damage to the amniotic sac, adverse effects in case of Rh conflict between mother and fetus, prolonged exposure to ultrasound on the fetus, and some deviations in fetal development are possible. Sometimes, for a number of technical reasons, it is not possible to analyze tissue samples. To summarize, 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 be aware of it.

The main advantage of chorionic villus biopsy is that the diagnosis of a severe disabling disease in the fetus can be established before the 12th week of pregnancy. At this stage, termination of pregnancy occurs with fewer complications for the woman, and the stress load on family members is also reduced.

A referral for prenatal diagnosis using chorionic villus 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 seek medical genetic consultation as early as possible.

Placentogenesis

Another invasive prenatal diagnosis. The technique for carrying them out is universal: puncturing the woman’s anterior abdominal wall with a needle and, under the control of an ultrasound machine, taking a piece of the placenta (with placentocentesis) or umbilical cord blood of the fetus (with cordocentesis).

Placentocentesis is usually performed in the second trimester of pregnancy, as is amniocentesis. Cordocentesis is most often performed after the 20th week of pregnancy. Both procedures have proven to be quite safe for women and fetuses. The studies are performed under anesthesia, on an outpatient basis or with short-term hospitalization.

Complications after prenatal diagnostic methods are very rare. This is a significant advantage of these methods. The disadvantage is the long period of pregnancy at which these studies are carried out. If the diagnosis of gross pathology is confirmed, termination of pregnancy during this period requires long-term hospitalization and is fraught with complications.

Indications for these prenatal diagnostic studies are usually established by a geneticist during medical genetic counseling.

Amniocentesis

It is also an invasive method of prenatal prenatal diagnosis. When performing amniocentesis under the control of an ultrasound machine (so as not to harm 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 a syringe through a needle.

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

determining the degree of maturity of the fetal lungs
definition oxygen starvation fetus
determination of the severity of Rh conflict between mother and fetus
more effective diagnosis of hereditary metabolic diseases
diagnosis of developmental defects (for example, defects in neural tube closure)

However, there are also some disadvantages:

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

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

Amniocentesis is usually performed at 15–16 weeks of pregnancy. Indications for its implementation are usually established by a geneticist during medical genetic counseling.

Cordocentesis

The method refers to invasive prenatal diagnostics, which represent, to a certain extent, surgical intervention. It involves inserting a special needle into the uterine cavity to collect placental villi, amniotic fluid or umbilical cord blood for further various tests. The need for invasive prenatal or so-called prenatal diagnostics is due to the possibility of preventing the birth of children with various congenital or hereditary diseases.

The diagnostic capabilities of cordocentesis are somewhat greater than those of 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

Prenatal screening results vary high level reliability and validity. They can both refute fears of the presence of pathology and prepare parents for the birth of a sick child.

Diagnostic procedures must be carried out taking into account the main ethical principles:

Availability. All women who have the means to do so should undergo research medical indications. Lack of finance should not be an obstacle to the procedure.
Voluntariness. Doctors are obliged to explain to the pregnant woman and her husband the need to undergo the study and the degree of risk of giving birth to a sick child. However, all appointments are advisory in nature, and the final decision on the need for them is made by the spouses.
Doctors are obliged to provide the family with complete information about the condition of the fetus. Parents should also have a complete understanding of the nature of their unborn child’s disease, the characteristics of its development, treatment methods and further prognosis.
Prenatal diagnostic procedures are carried out primarily to women who have medical indicators for this. Many impressionable women increased level anxiety disorders who are not at risk can also undergo these studies, but with full information about their possible consequences.
The decision to terminate a pregnancy can be made solely by the woman herself and her family members.
If the family decides not to terminate the pregnancy, the doctor must familiarize the parents with the features 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 to diagnostic procedures is decided jointly by an obstetrician-gynecologist, geneticist, neonatologist, and pediatric surgeon, taking into account the wishes of the parents themselves.

Invasive procedure

Invasive procedure(from New Latin invasivus; from invado - “I go inside”) - medical procedure associated with penetration through the natural external barriers of the body (skin, mucous membranes).

An example of the simplest invasive procedure is any injection, the most complex is surgery. This is the main way in which a surgeon, as opposed to a therapist, provides care to a patient.

Invasive procedures can also be used for diagnosis. Examples of invasive tests are invasive cardiac electrophysiological testing and invasive genetic testing of the embryo.

Notes

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Amniocentesis— collection of amniotic fluid for biochemical, hormonal, immunological, cytological and genetic studies, allowing one to judge the condition of the fetus. Indications for amniocentesis are: isoserological incompatibility of the blood of mother and fetus, chronic fetal hypoxia (post-term pregnancy, OPG-gestosis, extragenital diseases of the mother, etc.), establishing the degree of fetal maturity, antenatal gender diagnosis, cardiac examination for fetal malformations, microbiological study.

Depending on the puncture site, transvaginal and transabdominal amniocentesis are distinguished. Transvaginal amniocentesis is recommended for pregnancy 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 fetus

During transabdominal amniocentesis, after treating the anterior abdominal wall with an antiseptic solution, anesthesia of the skin, subcutaneous tissue and subgaleal space is performed with a 0.5% novocaine solution. For the study, at least 40 ml of amniotic fluid is required. The puncture site on the anterior abdominal wall is treated with an antiseptic and an aseptic sticker is applied. Transvaginal amniocentesis is performed through the anterior vaginal fornix, cervical canal, or posterior vaginal fornix. The choice of insertion site for the puncture needle depends on the location of the placenta. After preliminary sanitation of the vagina, the cervix is fixed with bullet forceps, moved up or down, depending on the method chosen, and the vaginal wall is punctured at an angle to the uterine wall. When a needle penetrates 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. In a full-term pregnancy, the pH of the amniotic fluid is 6.98-7.23.

The most informative values for diagnosing fetal hypoxia are pH (less than 7.02), pCO2 (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 110 mmol/l). One of important indicators Metabolism in amniotic fluid is considered to be creatinine, the concentration of which increases as pregnancy progresses 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 toxicoses pregnant women.

An increase in protein content in amniotic fluid may indicate hemolytic disease, intrauterine fetal death, anencephaly and other fetal developmental abnormalities. A glucose level in amniotic fluid of 15 mg/100 ml and above is a sign of fetal maturity, below 5 mg/100 ml is its immaturity. During postterm pregnancy, glucose concentration decreases by 40% due to a decrease in glycogen content in the placenta due to degenerative changes.

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

In order to diagnose the degree of fetal maturity, a cytological examination of amniotic fluid is performed. The main source of cellular composition of amniotic fluid is skin and epithelium urinary tract fetus It includes the epithelium of the amnion, umbilical cord and oral cavity of the fetus. To obtain and study the sediment, the amniotic fluid is centrifuged at 3000 rpm for 5 minutes, the smears are fixed with a mixture of ether and alcohol, then stained using the Garras-Shor method, Papanicolaou or 0.1% solution of Nile blue sulfate, which stains anucleate lipid-containing cells ( product sebaceous glands fetal skin) in Orange color(so-called orange cells).

The percentage of orange cells in the smear corresponds to the maturity of the fetus: up to 38 weeks of pregnancy, their number does not exceed 10%, over 38 weeks - reaches 50%. To assess fetal lung maturity, amniotic fluid phospholipid concentrations, particularly the lecithin/sphingomyelin (JI/C) ratio, are measured. Lecithin, a saturated phosphatidylcholine, is the main active principle of surfactant. The values of the L/S ratio are interpreted as follows:

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

In everyday practice they use qualitative assessment ratio of lecithin and sphingomyelin (foam test). For this purpose, add 3 ml of ethyl alcohol to a test tube with 1 ml of amniotic fluid and shake the test tube for 3 minutes. The resulting foam ring indicates the ripeness of the fruit ( positive test), lack of foam ( negative test) indicates immaturity of the lung tissue.

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

1) woman’s age over 35 years (taking into account high risk formation of trisomy on 21 pairs of chromosomes);

2) the presence of chromosomal diseases in children born earlier;

3) suspicion of diseases linked to the X chromosome in the mother.

Complications of amniocentesis: premature rupture of amniotic fluid (usually with transcervical access), injury to fetal vessels, injury to the mother’s bladder and intestines, chorionic amnionitis; less often - premature birth, placental abruption, fetal injury and umbilical cord damage. However, thanks to the widespread introduction of ultrasound guidance, complications of amniocentesis are extremely rare.

Chorionic villus biopsy- an operation whose purpose is to obtain cells villous chorion for fetal karyotyping and determination of chromosomal and gene abnormalities (including determination of hereditary metabolic disorders). Samples are taken transcervically or transabdominally between 8 and 12 weeks of pregnancy under ultrasound scanning guidance. Complications of chorionic villus sampling may include intrauterine infection, bleeding, spontaneous miscarriages, hematomas. Later complications include premature birth, low birth weight (< 2500 г), пороки развития плода. Перинатальная смертность достигает 0,2-0,9%.

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

Selected lectures on obstetrics and gynecology

Ed. A.N. Strizhakova, A.I. Davydova, L.D. Belotserkovtseva