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Invasive methods of prenatal diagnosis. Invasive and non-invasive diagnostic methods during pregnancy

Invasive methods of prenatal diagnostics are methods of obtaining samples of cells and tissues of the embryo, fetus and provisional organs (placenta, membrane) with subsequent study of the materials obtained. Currently, the following invasive methods are used in world practice: chorion - and placentobiopsy, obtaining amniotic fluid (amniocentesis), fetal tissue biopsy, fetal blood sampling (cordocentesis). Invasive methods must be safe for the pregnant woman and the fetus and be applicable early in pregnancy.

Amniocentesis (puncture of the fetal bladder) in order to obtain amniotic fluid and exfoliated cells of the amnion and fetus in it has been used for prenatal diagnosis since the early 70s. The procedure is performed at 15-18 weeks of pregnancy. A puncture of the fetal bladder is performed through the anterior abdominal wall (less often a transvaginal approach is used) under ultrasound control. Currently, with the help of amniocentesis, they diagnose all chromosomal abnormalities, over 60 hereditary metabolic diseases, incompatibility of the mother and the fetus for erythrocyte antigens.

Chorion - and placentobiopsy have been used since the late 1980s. These methods are used to obtain a small amount of chorionic villi or pieces of the placenta between the 8th and 16th week of pregnancy. There are no abnormalities of the placenta, fetal growth, the appearance of congenital malformations and an increase in prenatal mortality after chorionic biopsy. Unlike amniocentesis, the possibility of conducting a study in the first third of pregnancy allows it to be interrupted (if indicated) at an earlier date. However, the risk of complications with chorionic biopsy is greater than with amniocentesis.

Cordocentesis - taking blood from the umbilical cord is performed from the 20th week of pregnancy. The procedure is carried out under ultrasound control. Blood samples are an object for cytogenetic (lymphocytes are cultivated), molecular genetic and biochemical methods for diagnosing hereditary diseases.

Fetal tissue biopsy as a diagnostic procedure is carried out in the second trimester of pregnancy under ultrasound control. For the diagnosis of severe skin lesions (ichthyosis, epidermolysis), a biopsy of the fetal skin is performed, followed by a pathomorphological examination.

Fetoscopy (insertion of a probe and examination of the fetus) with modern flexible optical technology does not present any great difficulties. However, the method of visual examination of the fetus to detect congenital malformations is used only for special indications. It is performed between the 18th and 19th weeks of pregnancy. Fetoscopy requires the introduction of an endoscope into the amniotic cavity, which can cause complications of pregnancy. Miscarriages occur in 7-8% of cases.

Preplacental diagnostics

Since the mid-80s, research has been carried out in the direction of preimplantation diagnostics. At the same time, it is proposed to use the embryo at the early stages of development as an object for diagnosing hereditary diseases. Such diagnostics refers to the methods of primary prevention of hereditary diseases. Thanks to it, it is possible to avoid repeated abortions in families with a high risk of hereditary pathology. Obtaining preimplantation embryos is possible in two ways: non-surgical uterine lavage and in vitro fertilization.

The second method - in vitro fertilization and zygote crushing is well known and has long been used in obstetric practice in cases of overcoming infertility caused by obstruction of the fallopian tubes.

Diagnostics at the level of one cell is currently possible for some diseases. It is carried out using microanalytical methods. There are reports of successful diagnosis at the preimplantation stage of diseases such as Marfan's syndrome, myotic dystrophy, cystic fibrosis, thalassemia, Huntington's chorea, Duchenne muscular dystrophy and a number of other diseases. It is hoped that in the near future the methodological possibilities of preimplantation diagnostics will expand both in the field of obtaining diagnostic material and analytical methods.

CONCLUSION

In the course of our work, we faced the following tasks:

1. Analyze the literature on the assessment of the condition of the fetus.

2. Describe the methods of prenatal diagnosis.

3. To characterize various modern methods of assessing the condition of the fetus.

In conclusion, we came to the following conclusions.

The most significant trends in the development of prenatal medicine are less invasiveness, more informational content, the earliest possible examination period and the minimum risk to the fetus.

Timely diagnosis of fetal malformations and chromosomal abnormalities allows a decision to be made on the advisability of prolonging pregnancy until the fetus reaches viability.

Thanks to the success of reproductive biology and the introduction of new technologies into clinical practice, there has been significant progress in the accumulation and use of knowledge about the laws of development of the embryo and fetus.

Ultrasound procedure is the most reliable and accurate method of antenatal diagnosis of fetal health.

The method allows performing dynamic fetometry, assessing the general and respiratory movements of the fetus, fetal cardiac activity, thickness and area of \u200b\u200bthe placenta, the volume of amniotic fluid, and measuring the rate of fetal-uterine circulation.

In clinical practice, the most widespread are external sensors, the use of which has practically no contraindications and is devoid of any complications or side effects.

In modern fetal cardiac monitors, an indicator is provided that demonstrates the quality of recording fetal heartbeats. The use of external cardiotocography allows continuous monitoring of the fetal cardiac activity for a long time.

Thus, cardiotocography, especially in the presence of computer analysis, provides valuable information about the condition of the fetus.

Currently, one of the fairly common methods for assessing fetal cardiac activity are electrocardiography (ECG) and phonocardiography (PCG). Distinguish between direct and indirect fetal ECG. An indirect ECG is performed when electrodes are placed on the anterior abdominal wall of a pregnant woman. This method is used mainly in the antenatal period.

When choosing a rational screening program for pregnant women, it should be remembered that the accuracy of prenatal diagnosis increases with the use of several diagnostic tests and a careful assessment of several risk factors.

To assess the nature of the course of pregnancy and the state of the fetus, in a number of cases, invasive diagnostic methods are used, a number of which are performed with echographic control.

A significant part of prenatal invasive studies is the cytogenetic diagnosis of chromosomal diseases. In these cases, the indications for its implementation are: the age of the mother is 35 years and older; the birth of a child with a chromosomal pathology in the family; carriage of a family chromosomal abnormality; suspicion of the presence of congenital malformations in the fetus; the presence of echographic signs of chromosomal pathology; deviation of serum maternal markers levels.

The choice of the method of invasive diagnostics is determined by the corresponding indications, the duration of pregnancy, the condition of the pregnant woman, and her consent is also taken into account.

In the first trimester of pregnancy, transcervical or transabdominal aspiration of chorionic villi is most often performed. In the second trimester, amniocentesis, transabdominal aspiration of the placental villi and transabdominal cordocentesis (puncture of the umbilical cord vessels) are performed.

Invasive interventions are carried out in the presence of the results of a gynecological examination of a pregnant woman and laboratory data (blood and urine tests, tests for syphilis, HIV, hepatitis B and C, analysis of a smear of vaginal discharge, etc. - according to indications).

4.8.1. Study of amniotic fluid

Determination of such characteristics of amniotic fluid as quantity, color, transparency, cytological and biochemical composition, hormone content, in some cases is of great diagnostic value for assessing the nature of the course of pregnancy and the state of the fetus.

It is possible to determine the volume of amniotic fluid using both clinical research methods (measuring the circumference of the abdomen and the height of the uterine fundus, palpation), and using ultrasound diagnostics. When using these methods, the most accurate results, indicating an abnormal amount of amniotic fluid, can be obtained with pronounced low water or polyhydramnios.

In borderline situations, manifested by relative or moderate low water or polyhydramnios, the assessment of the volume of amniotic fluid is largely subjective. Even with ultrasound with the calculation of the amniotic fluid index, the diagnostic value of the method is low.

If an abnormal amount of amniotic fluid is suspected, an important diagnostic criterion is dynamic monitoring of the rate of change in its amount.

With the help of amnioscopy, a transcervical examination of the lower pole of the fetal bladder is carried out, which makes it possible to determine the color of amniotic fluid, their consistency, to identify an admixture of meconium or blood, the presence of flakes of cheese-like lubricant. The indications for this diagnostic procedure are the suspicion of chronic fetal hypoxia, prolonged pregnancy, isoserological incompatibility of the blood of the mother and the fetus. Contraindications include inflammatory diseases of the vagina and cervix, placenta previa.

It is possible to obtain amniotic fluid for biochemical, hormonal, immunological, cytological or genetic research using amniocentesis.

Figure: 4.42. Amniocentesis. Transabdominal access.

1 - cervix; 2 - the vagina; 3 - amniotic fluid; 4 - uterus; 5 - placenta.

The indications for this diagnostic procedure are most often the need for cytogenetic diagnosis of chromosomal diseases. In more rare cases, amniocentesis is performed with fetal hypoxia, isoserological incompatibility of the blood of the mother and the fetus, to assess the degree of maturity of the fetus (by the ratio of the concentration of lecithin and sphingomyelin or by the number of nuclear-free lipid-containing "orange" cells), the need for microbiological examination of amniotic fluid. Contraindications - the threat of termination of pregnancy and infection of the genital tract. The procedure is performed under ultrasound guidance, choosing an access depending on the location of the placenta and fetus. In this case, both transabdominal (Fig. 4.42) and transcervical amniocentesis are performed.

Among the complications of this manipulation are premature rupture of amniotic fluid, premature birth, fetal injury, placental abruption, cord injury, injury to the bladder and intestines of the mother, chorioamnionitis.

4.8.2. Fetal blood test

The results of the study of fetal blood obtained from the umbilical cord or from the vessels of the skin of the head provide reliable and important information about its condition.

Blood from the vessels of the umbilical cord is obtained by transabdominal cordocentesis, which consists in puncture of the vessels of the umbilical cord under echographic control.

The indications for this diagnostic procedure are the need to diagnose chromosomal diseases in the fetus by karyotyping, suspicion of intrauterine infection, fetal hypoxia, isoserological incompatibility of the blood of the mother and the fetus. Cordocentesis is performed after 18 weeks of pregnancy. Contraindications are the same as for amniocentesis.

Among the most common complications are premature rupture of amniotic fluid, premature termination of pregnancy, bleeding from a punctured vessel.

During childbirth, for the study of fetal capillary blood, it is obtained from the vessels of the scalp using an amnioscope. In the obtained blood sample, the pH value (concentration of free hydrogen ions) is estimated. At a pH value of more than 7.25, it is considered that the fetus does not suffer from hypoxia and its condition is classified as normal. If the pH value is in the range from 7.20 to 7.24, then it is considered that the fetus is experiencing moderate hypoxia and measures must be taken to increase the degree of its oxygenation. A pH value below 7.20 indicates severe fetal hypoxia, accompanied by metabolic acidosis, which requires urgent delivery.

4.8.3. Oxygen saturation of the fetus during labor

One of the modern objective and safe methods for assessing the functional state of the fetus during childbirth is pulse oximetry, which is a non-invasive method for continuous determination of fetal oxygen saturation (SpO2), which reflects the saturation of arterial blood hemoglobin with oxygen.

The saturation value is expressed as a percentage of the level of oxyhemoglobin to the sum of the concentrations of oxyhemoglobin and deoxygenated hemoglobin (excluding carboxyhemoglobin and methemoglobin):

In modern devices, the method for determining the value of saturation is based on two principles. First, oxyhemoglobin and deoxygenated hemoglobin have different ability to absorb and reflect light depending on its wavelength. In the sensors used, LEDs emit red and infrared light alternately, which have different wavelengths.

Secondly, the volume of arterial blood in the tissues and, accordingly, the ability to absorb light by the blood changes due to its pulsation caused by heartbeats. During systole, due to an increase in blood volume in the tissue, the absorption of light increases, and in diastole, accordingly, decreases. In this case, the amount of reflected light also changes in inverse proportion.

In devices used for research, the pulse oximeter sensor should be in direct contact with the fetal skin. The photodetector of the sensor, located in the same plane with the light-emitting elements, measures the reflected light, the amount of which is inversely related to the amount of absorbed light.

By analyzing the characteristics of the red and infrared light reflected from the blood flow located under the sensor, the pulse oximeter estimates the saturation value during the study.

Modern pulse oximeters are calibrated according to the standards of saturation values \u200b\u200bmeasured in fetal blood samples during childbirth, which reliably reflect fetal hypoxia.

Pulse oximetry is used in childbirth with head presentation of the fetus, the absence of the fetal bladder and the opening of the cervix by at least 3 cm. Contraindications to the use of the technique are bleeding from the genital tract, placenta previa, multiple pregnancies, the presence of infections, a scar on the uterus.

Before the start of the study, the pulse oximeter sensor, inserted into the uterine cavity, is placed on the cheek of the fetus or in the temporal part, free of hair, which eliminates the distortion of the reflected light signal.

The curved shape of the working surface of the sensor and the pressure from the walls of the uterus allow it to be tightly fixed on the fetal head at the application site. At the same time, the sensor does not injure the tissues of the birth canal of the mother and fetal tissue. The SpO2 registration time is 60 minutes or more. In some cases, the sensor can be poorly held between the fetal head and the inner surface of the uterine wall if the fetal head is not inserted correctly.

In the normal course of labor, the saturation value varies on average from 45 to 65% and gradually decreases by 5-10% from their beginning to completion.

In this case, certain changes in the value of saturation occur depending on the phases of uterine contraction. The highest SpO2 values \u200b\u200bare recorded during the pause between uterine contractions. At the beginning of the contraction, there is a slight decrease in the value of saturation, followed by an increase at the peak of the contraction (comparable to the SpO2 value between contractions) and a significant decrease at the end of the contraction.

The nature of changes in the value of saturation during contractions is due to a number of factors: changes in hemodynamics in the uterine arteries and in the arteries of the umbilical cord, changes in the value of intrauterine pressure, changes in the heart rate of the fetus.

With fetal hypoxia, saturation indices decrease on average by 15-20% compared to the norm. The degree of decrease in fetal saturation during labor is in direct proportion to the severity of hypoxia.

When the condition of the fetus is impaired, there is also a pattern of changes in the SpO2 value depending on the phases of uterine contraction. The decrease in the SpO2 value, noted at the beginning of the contraction, becomes most pronounced at the peak of uterine contraction, followed by an increase as the uterus relaxes. The more pronounced hypoxia, the lower the SpO2 value at the peak of the contraction. Such changes are an unfavorable prognostic sign associated with a high risk of developing complications of hypoxic genesis in the fetus.

The fetal pulse oximetry method has a number of advantages over other methods for assessing the state of the fetus during labor, as it responds more quickly to changes in the oxygen content in the fetal blood. However, pulse oximetry is most expedient to use if, according to CTG, there are signs indicating severe fetal abnormalities. Saturation less than 30% is critical for the fetus.

A rapid decrease in the value of saturation to a level of less than 30%, especially in combination with unfavorable signs of CTG (bradycardia, decreased variability of the basal rhythm, deep late decelerations), is an indication for emergency abdominal delivery. However, if possible, then it is advisable to assess the pH of the blood from the vessels of the skin of the fetal head. If at the same time the pH value is more than 7.25, then you can continue the management of labor through the natural birth canal. At a pH of 7.24-7.20 and below, emergency abdominal delivery is necessary.

If, against the background of unfavorable signs of CTG, the saturation value is more than 30%, then in fact there is an adequate supply of oxygen to the fetus and it does not experience hypoxia.

There is a clear relationship between the degree of saturation of hemoglobin with oxygen in the fetal arterial blood during childbirth and the condition of the newborn. Low FSpO2 values \u200b\u200b(less than 30%) also correlate with low blood pH levels of newborns (pH increase in base deficiency (BE) and a decrease in the number of buffer bases (BB), which collectively indicate hypoxia in newborns, accompanied by metabolic acidosis. the composition of blood in newborns indicates the degree of hypoxia in the intranatal period, which is confirmed by a low Apgar score at birth and clinical manifestations of complications of hypoxic genesis.

Consequently, the results of fetal pulse oximetry make it possible not only to timely resolve the issue of labor management and choose the optimal delivery method, but also to predict perinatal outcomes.

The pulse oximetry method is easy to use and can be used in obstetric institutions of any level. The use of fetal pulse oximetry does not increase the risk of intrauterine infection of the fetus and does not increase the frequency of postpartum pyoinflammatory complications in postpartum women.

4.8.4. Chorionic villus sampling

With the help of this diagnostic procedure, chorionic villus cells are obtained for karyotyping the fetus if it is necessary for the cytogenetic diagnosis of chromosomal diseases, as well as for determining the sex of the fetus. Manipulation is carried out both transcervically and transabdominally in early pregnancy (10-14 weeks) or transabdominally at 20-24 weeks under echographic control. Chorionic tissue is collected by aspiration. Contraindications are the threat of termination of pregnancy and infection of the genital tract.

Complications include bleeding, the formation of subchorial hematomas, termination of pregnancy, and intrauterine infection.

4.8.5. Fetoscopy

To clarify the presence of an anomaly in the development of the fetus by direct examination, fetoscopy is used. With this method, parts of the fetus are examined through an endoscope transabdominally inserted into the amniotic cavity and, if necessary, samples of amniotic fluid, blood or fetal tissue are taken. Contraindications - the threat of termination of pregnancy and intrauterine infection.

Among the complications of fetoscopy, there is an untimely rupture of amniotic fluid, premature termination of pregnancy, less often bleeding and intrauterine infection.

Invasive diagnostic methods (IMD) are a combined group of studies that make it possible to obtain biological material of fetal origin for analysis (amniotic fluid, chorionic or placental villi, fetal skin and blood). 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 a woman's diseases and 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 abortion 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 the general condition of the pregnant woman.

Dates

There are different classifications of invasive diagnostic methods.

By timing, they are distinguished:

  • IDI performed in the first trimester of pregnancy:
  1. chorionic villi - cells of the villous part of the chorion (the outer shell of the fetus, which later transforms into the placenta) are taken to determine the chromosomal set of the fetus. Samples are taken between 8 and 12 weeks of pregnancy.
  2. - an operation with 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:
  1. Amniocentesis – Amniotic fluid collection is usually between 17 and 22 weeks of gestation, but sometimes the test is taken up to 34 weeks.
  2. – 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 gestation and, if necessary, up to delivery.
  3. – procedure for taking placenta cells for analysis for the diagnosis of chromosomal diseases. Spend at 18 - 22 weeks.
  4. – obtaining fetal blood for the diagnosis of hereditary blood diseases, intrauterine infection, as well as the treatment of hemolytic disease of the fetus. Applied from 18 weeks of pregnancy.
  5. – direct examination of the fetus to detect congenital malformations. Using an endoscope, it is also possible to take a piece of the fetal skin for examination. Usually it is carried out at 18-24 weeks.

importantIn the third trimester of pregnancy, as a rule, IMD is not used due to the high risk of premature birth. But sometimes, in the presence of strict indications, it is possible to perform amnioscopy, amniocentesis and cordocentesis before delivery.

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 age of a woman 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 with;
  • Deviation in the level of serum proteins in the mother's blood;
  • 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;
  • A history of spontaneous miscarriages, stillbirths, primary amenorrhea, primary infertility in spouses;
  • Unfavorable effects of environmental factors in the early stages of pregnancy (radiation exposure, inhalation of vaporous poisons, etc.);
  • Taking embryotoxic drugs in early 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,
  • fetal injury,
  • 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 to weigh the pros and cons as calmly as possible and only then refuse to conduct the research. Very often, pregnant women do not understand that such procedures are not simply prescribed, and that a serious fetal disease that is not detected in time can threaten not only the health, but also the life of a woman.

Non-invasive methods

Prenatal diagnostic methods

Preimplantation diagnostic methods

Special clinical, instrumental and clinical laboratory methods

Special clinical-instrumental and clinical-laboratory methods include methods of preimplantation and prenatal diagnosis of hereditary and congenital diseases. Among these methods are distinguished: non-invasive (without penetration into the body) and invasive (with penetration into the body).

Preimplantation diagnostics is a study of a DNA molecule in embryonic cells at an early stage of zygote development -

diy blastocyst (6-8 cells obtained during fertilization in vitro- non-invasive method) or using uterine lavage in the period 90-130 hours after fertilization (invasive method).

The essence of these methods is that with the help of microsurgical intervention, one or two cells are separated from the embryo for subsequent genetic analysis.

The rest of the germ cells are frozen until the end of the analysis. If hereditary pathology is excluded in the analyzed cells, then the remaining cells are thawed and conditions are created for them that are optimal for normal development, after which they are implanted into the uterus during the corresponding period of the menstrual cycle.

The advantage of these methods is the ability to terminate a pregnancy if a hereditary pathology is detected in the embryo.

The disadvantage of these methods is the low percentage of successful implantations (only 10-20%), as well as possible complications during pregnancy after successful implantation of the embryo.

Using this method, for example, diagnostics of Marfan syndrome based on reverse transcription PCR is feasible, which makes it possible to identify mutations in the fibrillin gene.

Non-invasive PD methods are as follows:

Ultrasound is the most effective method. It is performed at various stages of pregnancy, including at 18-22 weeks - the first ultrasound, 25-29 weeks - the second ultrasound, 32-36 weeks - the third ultrasound. Ultrasound reveals: congenital heart defects, neural tube defects, polycystic kidney disease, skeletal dysplasias, cleft upper lip, soft and / or hard palate, cellular hygroma, meningocele, microcephaly, polydactyly, facial and external genital defects. Ultrasound can be performed early in pregnancy (12-14 weeks) in order to detect neural tube defects.

Electro (echo) fetal cardiography. It is used in the third trimester of pregnancy to diagnose congenital heart defects.

Fetoscopy and fetoamniography. They are used in the II trimester of pregnancy for biopsy of placenta cells and fetal skin cells (epidermolysis bullosa).


Invasive PD methods are based on two approaches, with the help of which embryo and fetal cells are taken (under ultrasound control).

First approach- transcervical (through the vagina and cervix).

Second approach -transabdominal (through the anterior abdominal wall).

In the early stages of pregnancy (8-12 weeks), cells isolated from the material of chorionic villi (chorionic biopsy) or placenta (placenta biopsy) are used for laboratory analysis. In the later stages of pregnancy, cells obtained from the amniotic (amniotic) fluid of the fetus, or cells isolated from the umbilical cord blood of the fetus (see "cordocentesis") are used for laboratory analysis.

Let's briefly review the main invasive methods.

Amniocentesis. It is carried out for periods of pregnancy up to 12 weeks, as well as for 16-18 weeks. Allows you to analyze the state of the karyotype and DNA molecules in the cell culture of the embryo or fetus; in the amniotic fluid of the fetus, the level of alpha-fetoprotein (AFP) is determined, and the level of 17-hydroxyprogesterone in the fetal serum.

Chorionic biopsy. It is carried out at 8-12 weeks of pregnancy. Native cells and cells in chorionic tissue cultures are analyzed. Everything is investigated as in amniocentesis, except

Cordocentesis. It is carried out at 20-22 weeks of pregnancy by analyzing the fetal cord blood taken from the vessels of the umbilical cord under ultrasound control.

Both amniocentesis and chorionic biopsy are used in the developed world in about 10% of all pregnancies. These methods are associated with the lowest risk to the embryo and fetus. With their help, Down, Patau and Edwards syndromes, triplo-X, Y-chromosome abnormalities, as well as more than 100 MB (Tay-Sachs disease, hypophosphatemia, leucinosis, methylmalonic acidemia, adenosine deaminase deficiency, citrullinemia, etc.) are diagnosed.

The doctor makes the final diagnosis of hereditary and congenital diseases when the clinical and paraclinical stages of examination of the proband are completed.

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

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.

With transabdominal amniocentesis, after treatment of the anterior abdominal wall with an antiseptic solution, anesthesia of the skin, subcutaneous tissue and subgaleal space is performed 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 injection site for the puncture needle depends on the location of the placenta. After preliminary sanitation of the vagina, the cervix is \u200b\u200bfixed with bullet forceps, shifted up or down, depending on the selected 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 (less than 7.02), pCO 2 (over 7.33 kPA), p02 (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 the important indicators of metabolism in amniotic fluid is 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 of 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 degenerative 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, a cytological examination of the amniotic fluid is carried out. The main source of the cellular composition of the amniotic fluid is 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 of the sebaceous glands of the fetal skin) in orange (the so-called orange cells). The percentage of orange cells in a smear corresponds to the maturity of the fetus: before 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 / S) ratio. Lecithin, saturated with phosphatidylcholine, is the main active principle of the surfactant. The L / C ratio values \u200b\u200bare interpreted as follows:

  • L / S \u003d 2: 1 or more - mature lungs; only in 2% of cases, newborns are at risk of developing respiratory distress syndrome;
  • L / C \u003d 1.5-1.9: 1 - the likelihood of developing respiratory distress syndrome is 50%;
  • L / C \u003d 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, 3 ml of ethyl alcohol is added to a test tube with 1 ml of amniotic fluid and the test tube is shaken for 3 minutes. The formed ring of foam indicates maturity of the fetus (positive test), the absence of foam (negative test) indicates immaturity of the lung tissue.

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

  • the woman's age is over 35 years (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 rupture of amniotic fluid (more often with transcervical access), injury of fetal vessels, injury of the urinary bladder and 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). Sampling is performed transcervically or transabdominally in the period from 8 to 12 weeks of pregnancy under the control of ultrasound scanning. Complications of chorionic villus sampling can be intrauterine infection, bleeding, spontaneous miscarriages, hematomas. Later complications include premature birth, low birth weight (

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 the umbilical cord vessels, intrauterine growth retardation.

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 of the fetus can be corrected before birth, which prevents the birth of children in serious condition. The first intrauterine surgery - replacement fetal blood transfusion - was performed for severe hemolytic disease of the fetus by cordocentesis. However, the high frequency of intrauterine fetal death does not allow widespread use of this method.

Another area of \u200b\u200bfetal 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 at intrauterine treatment of a fetus with hydrocephalus, which boiled down to the implantation of a ventriculoamniotic shunt to reduce intracranial pressure. Despite the encouraging results of experimental studies, 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 moderate to severe physical and mental impairments.

Surgical aids for reverse arterial perfusion in twins (a specific pathology in multiple pregnancies, characterized by vascular messages between fetuses, which can cause the death of one or the other twin), are promising. 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 perform ligation of communicating vessels in the umbilical cord or their laser coagulation, performed under endoscopic control.