Chorionic villus biopsy - what is it? Chorionic villus sampling: important or not? Chorionic villus biopsy timing

When a young woman finds out that she will soon become a mother, many changes begin in her life, including the need for constant medical supervision.

Pregnant women, even if everything is in order with their health, should quite often take a variety of laboratory tests and undergo some examinations, but if the attending physician who monitors the course of pregnancy deems it necessary, then additional examinations and tests may be prescribed, including including chorionic villus biopsy.

What kind of BVH test is this and why is it needed?

This test is performed to detect abnormalities during fetal development. The test is carried out at very early stages of pregnancy - in the first trimester, and this is very important, because in the early stages it is possible to terminate the pregnancy if the test result indicates that the unborn child will be born with serious pathologies. A negative result of this test makes it possible to feel calmer throughout your pregnancy.

Attention! Chorionic villi are the smallest outgrowths (almost villi) found in the placenta. At the genetic level, the chorionic villi (the outer membrane of the embryo) absolutely correspond to the developing fetus.

Chorionic villus biopsy makes it possible to determine with a high degree of probability that the unborn child has Down syndrome and other developmental defects and/or diseases, many of which are very dangerous. However, we should not forget that no test provides a 100% result and a complete guarantee of accuracy.

Attention! Chorionic villus sampling is performed between the 10th and 12th week of pregnancy, that is, in the last weeks of the first trimester of pregnancy.

Unfortunately, chorionic villus biopsy cannot detect neural tube defects, so this test does not diagnose such a complex pathology as congenital spinal hernia, which is detected using.

Indications for CVS

Since this test carries some risks and, in addition, it is a rather expensive procedure, chorionic villus biopsy is not prescribed to all pregnant women, but only in cases where the doctor has every reason to suspect something is wrong.

First of all, chorionic villus biopsy is prescribed in cases where, as a result of screening carried out in the first trimester of pregnancy, it is determined that the fetus can be detected.
Screening procedures that become the basis for prescribing a chorionic villus biopsy are an ultrasound examination of the fetal neck to identify the transparency of the cervical fold and the results of a blood test of a pregnant woman.
This test is also prescribed for pregnant women over 35 years of age, since at this age the risk of having a child with Down syndrome increases. The older the pregnant woman, the greater the risk of giving birth to a sick child - if the expectant mother is over 35 years old, then the probability of giving birth to a baby with Down syndrome is 1:350, and if the pregnant woman is over 40 years old, then this probability increases to 1:100.
The test allows you to identify hidden genetic disorders (hereditary family diseases), such as early childhood amaurotic idiocy, sickle cell disease, and abnormalities in the development of chromosomes.
A serious reason for prescribing a chorionic villus biopsy is the need to establish the sex of the fetus at the earliest stages, which occurs in cases where one of the parents is known to be a carrier of sexually transmitted anomalies.
For example, it could be hemophilia or Duchenne muscular dystrophy, which affects almost only men.
The test is required if one baby has already been born with Down syndrome or any other disorder at the chromosomal level.
The basis for chorionic villus biopsy is the result of an ultrasound examination, which reveals any predisposition of the fetus to the development of any defect.

Benefits of the procedure

Even taking into account some risks, the procedure has unconditional positive aspects.

First of all, if the biopsy result is negative, it can be assumed with a high degree of probability that the unborn child does not have pathologies at the gene and chromosomal level.
If the result is positive, that is, when pathologies are confirmed, you can decide to continue the pregnancy, understanding that a sick child will be born, or to terminate the pregnancy at a reasonable time.
If the decision is made to continue the pregnancy, there is time to prepare the family for the arrival of an unhealthy baby with defects.
In addition, there is time to find a suitable clinic for the birth, because the birth of such children has certain characteristics.

Complications and potential danger

The chorionic villus biopsy test is not considered completely safe, since after it is performed, miscarriage (spontaneous abortion) is possible. The probability of such an undesirable reaction is from one to four cases of spontaneous abortion per 400 procedures.

The material that is obtained from the chorion (the outer membrane of the fetus) is being studied. You can obtain such material in two ways. First, your doctor may perform a transcervical chorionic villus sampling, which involves inserting a probe into the placenta through the vagina and cervix. Secondly, a very thin and very long needle can be inserted into the placenta through the abdominal cavity, as during puncture of the amniotic sac.

One of the possible complications is that an infection may enter the uterus. And although the probability of such an outcome is negligible, it should still be taken into account.

Attention! An alternative to chorionic villus sampling can be amniocentesis, which is performed during the second trimester. Amniocentesis makes it possible to diagnose more than a hundred diseases that are transmitted at the genetic or chromosomal level, including Down syndrome and fetal neural tube defect. Amniocentesis is performed between the 15th and 20th weeks of pregnancy because by this time there is enough amniotic fluid to be used for the test.

Chorionic villus sampling (CVS) is a procedure for taking chorionic villi cells for analysis and identifying possible gene and chromosomal abnormalities in them. The chorion is the outer membrane of the fetus, covered with villi, which is closely adjacent to the uterus. Since it is of fruit origin, its cells carry complete information about any anomalies of the unborn child. By then it is completely transformed into the placenta. If for some reason it was impossible to do a CVS in a timely manner, then you can take a small piece of the placenta for examination. Read more about placentocentesis in the corresponding article.

Chorionic villus sampling is performed at 8 to 12 weeks of pregnancy.

Indications for CVS

Indications:

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;
Presence of signs of congenital pathology during ultrasound screening;
Consanguineous marriage;
The presence of a chromosomal rearrangement, hereditary disease or developmental defect in one of the spouses;
Presence of monogenic hereditary diseases in relatives (phenylketonuria, cystic fibrosis, spinal amyotrophy);
The need to determine the sex of the fetus, since some diseases are linked to the X chromosome and appear only in boys (hemophilia A and B, optic nerve atrophy);
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 the early stages of pregnancy (radioactive radiation, inhalation of vaporous poisons, etc.);
Taking embryotoxic drugs in early pregnancy;
X-ray examination in the early stages.

Contraindications to biopsy

Contraindications:

Inflammatory diseases of the vagina and cervix, or abdominal skin (depending on the puncture site).
A relative contraindication is the presence of HIV infection in a pregnant woman, as the likelihood of transmitting it to the fetus increases. If analysis is necessary, increase the dose of antiretoviral drugs.

Methods for taking chorionic villus sampling

Depending on the method of taking material for research, there are:

Transcervical approach– a thin flexible tube is inserted through the vagina and cervical canal into the uterine cavity and a piece of chorionic villi is carefully pinched off.
Transabdominal method– a puncture is made through the skin of the woman’s abdomen with a thin needle and a few chorion cells are collected into it.

Additionally The choice of method depends on the location of the chorionic villi. Regardless of the method of taking the analysis, the study is carried out under mandatory ultrasound control.

Complications after BVC

Early complications of biopsy:

Spontaneous miscarriage, according to two Russian multicenter studies, with transabdominal biopsy is 0.5 - 1.5%, and with transcervical biopsy it can reach 7.5%.
Intrauterine infection;
Bleeding from the puncture site;
Formation of parietal hematomas, which can provoke detachment of the ovum

Late complications:

Low body weight of the newborn (less than 2500g).

Chorionic villus biopsy, like other invasive methods of diagnosing the fetus, is carried out only with the consent of the pregnant woman. It should be borne in mind that with BVC, abnormalities of the neural tube of the fetus are not detected, so it is possible that amniocentesis will also have to be performed at 18–22 weeks of pregnancy (read more in the article “”) 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. Knowing the child’s illness, it is always easier to prepare for his birth and, if necessary, carry out treatment immediately after birth.

A mature placenta has the form of a disk with a diameter of 12-20 cm, a thickness of 2-4 cm, and a weight of 500-600 g. The placenta is divided into: chorionic (fetal) and basal (maternal) surfaces (plates). Between them is the villous chorion (placental parenchyma), placental septa and islands of extravillous trophoblastic cells. The umbilical cord is attached in the center of the chorionic plate or somewhat eccentrically. The membranes normally extend from the edge of the placenta.

Chorionic plate the outside is lined with amnionic epithelium, usually cubic, which can become cylindrical or flat. The cells are located on the BM. Underneath it lies dense connective tissue, in which there are fruit vessels. Between the chorionic plate and the intervillous space there is a subchorionic fibrinoid (Langhans layer).

Basal plate separates the fetus from the uterus. It is formed by a compact layer of the basal decidua into which anchoring villi grow. It has two layers of fibrinoid - Rohr's layer (internal towards the fetus) and Nitabuch's layer (external, located between the basal lamina, decidual cells and endometrial glands). Between the two layers of fibrinoid, anchor villi, foci of extravillous trophoblastic cells, scattered scanty lymphoid cell infiltrates and maternal blood vessels (spiral arteries and veins) are visible.

The term "fibrinoid" is used to describe the acellular, eosinophilic material that is formed by fetal and maternal components and consists of products of cell degeneration, hyaluronic, sialic acids, immunoglobulins, albumins, etc. Fibrinoid is a mechanical supporting scaffold as well as an immunological barrier that protects the fetus and placenta from maternal immunological reactions. Fibrinoid is also found in the intervillous space, in places merging with the villi. The extent of fibrinoid in all of these fields is variable and does not necessarily indicate pathology. This also applies to fibrinoid deposits in the subchorionic space and in the basal lamina.

Placental septa and islets of extravillous trophoblast. During embryogenesis, more trophoblast goes to build villi. Extravillous trophoblast forms the chorionic plate, smooth chorion, septa and islets. The septa extend from the basal lamina and divide the placenta into cotyledons (lobes or lobes). They rarely reach the fruiting plate and consist of extravillous trophoblastic cells (the so-called X cells). Islands of extravillous trophoblast are located randomly along the length between the maternal and fetal plates. They are built from X cells, fibrinoid and several decidual cells. X cells have secretory activity, and therefore cysts with a diameter of 4 cm or more often form in the center of the islets.

Placental parenchyma (villous chorion, cotyledons) represented by stem villi with smaller fruit vessels than in the chorionic plate, intermediate, terminal villi and intervillous space. The mature placenta has 10-40 cotyledons (placentons). In the center of each cotyledon there is a small number of closely packed mesenchymal (embryonic) and immature intermediate villi; at the periphery there are mature intermediate and terminal (end) villi. At the end of pregnancy, the villous tree is represented mainly by stem and terminal villi.

All villi have a general structure plan. The surface of the villus is formed by STP, followed by CTP. Trophoblastic BM (TFBM) delimits STF and CTP from the villous stroma. The STF has an uneven thickness and consists of several zones that pass into each other without sharp boundaries: epithelial plates, syncytium that does not contain nuclei, syncytium with a uniform arrangement of nuclei, and syncytium with an accumulation of nuclei. Epithelial plates form part of syncytiocapillary membranes (SCM) - the place of contact of the capillary wall in the terminal villus with the layer of cytoplasm of the chorionic epithelium. Syncyocapillary membranes are special fields of gas exchange between mother and fetus. Until the 32nd week of pregnancy, their number is small; by the end of pregnancy, 20% of the villi have them. Areas with accumulation of nuclei in the STF are divided into syncytial proliferating nodules and syncytial bridges. Syncytial nodules (SN) are formed by a cluster of nuclei located in 2-3 layers, one above the other. They can bulge or, conversely, press into the stroma of the villi; in the latter case, they are called syncytial buds (SB). Syncytial bridges are understood as syncytial connections between adjacent villi of the same villous or neighboring tree. In the area of the bridges there may be vessels that communicate between the capillaries of neighboring villi. It must be emphasized that all these structures look the same in tangential sections.

The cytotrophoblast is a discontinuous cell layer located beneath the STF. CTP cells, or Langhans cells, persist until the end of pregnancy, but their number is significantly reduced. In the mature placenta, about 1/5 of the surface of the villi has a two-layer trophoblast.

The villous stroma consists of fibroblasts, reticular cells, Kashchenko-Hoffbauer cells (KH cells), collagen, reticular fibers (elastic fibers are not found) and intercellular substance. In the terminal villi, the stroma is represented by dilated sinusoids formed by reticular cells and single collagen fibers.

Stem (supporting) villi(20-25% of all villi) originate from the chorionic plate and continue to approximately 2/3 of the thickness of the placenta. They are divided into branches of the 1st-3rd order depending on the diameter and type of fruit vessels. Stem villi of the 1st Order are localized in the subchorionic space. These are relatively short and wide villi with dense connective tissue stroma, centrally located arteries and veins. They are lined by a single layer of STF, which is often thinned, often with extensive defects covered by fibrinoid. Stem villi of the 2nd order are close in structure to those described above, but have a smaller diameter, and fruit vessels have a thinner wall, approaching the structure of small arteries and veins. These villi branch. 3rd order stem villi contain arterioles and venules, which are difficult to distinguish by structure.

Intermediate villi divided into mature and immature. Immature intermediate villi (0-5% of all villi) are a continuation of the stem villi. Appear around the 8th week of pregnancy and predominate in premature placentas. They are irregular in shape, with loose reticular stroma, capillaries and numerous channels containing KG cells. The chorionic epithelium is predominantly bilayered, with clearly visible CTP cells. BC may form on the surface. This section of the chorion provides branching and linear growth of the chorionic tree. Mature intermediate villi (approximately 25%) arise from immature intermediate villi. They are long, thin, with blood vessels that do not have tunica media and adventitia, with rare stromal canals, and without KG cells. These villi have endocrine and metabolic activity and regulate microcirculation.

Terminal villi(50% or more) - terminal (like grape branches) branches of mature intermediate villi. They have many capillaries, venous sinusoids and are the main site of gas exchange between the fetus and the mother and, together with the peripheral intermediate villi, participate in metabolism, the release of hormones and nutrition of the fetus.

Mesenchymal (embryonic) villi- these are large, multi-lobed villi that form the basis of the placental parenchyma in the first 7-8 weeks of pregnancy. They have a reticular stroma that persists until the 14th week; numerous stromal channels containing KG cells. Stromal channels are normal and not a sign of edema.

Morphological examination of the placenta reveals various changes.

The main criterion for differential diagnosis with intravital changes is the prevalence of morphological changes, since they are predominantly focal in nature. The villi undergo secondary changes due to obliteration of fetal vessels and decreased perfusion of the placenta.

Large (enlarged) placenta (hyperplasia, placental hypertrophy, giant placenta). Due to the variable amount of blood in the placenta, placental weight may not be an accurate marker for determining whether a placenta is large or small. A more accurate indicator is the fetal-placental coefficient (FPR) - the ratio of the weight of the fetus to the weight of the placenta, which in a full-term pregnancy is 7.0 (1: 7). The placenta is considered enlarged if its weight is 100-150 g higher than the average for a given period of pregnancy, i.e. in a full-term pregnancy, a placenta weighing 750 g or more is hyperplastic, with an AUC of less than 1:4.

Macroscopically: the placenta is pale and swollen. Microscopically: the villi are enlarged, both layers of trophoblast are clearly visible, the stroma is redundant, with an abundance of CG cells, and is often edematous. There are nuclear erythrocytes in the fetal vessels. A large placenta occurs with HDN, some intrauterine infections (toxoplasmosis, syphilis, parvovirus B19, CMV, rubella); diabetes mellitus (DM) and gestational diabetes; Congenital malformations of the fetus (especially congestive heart defects and cystic adenomatous pulmonary defects); congenital fetal tumors (neuroblastoma, teratoma, leukemia); congenital non-immune hydrops fetalis; congenital nephrotic syndrome; twin transfusion syndrome; tumors of the placenta, Wiedemann-Beckwith syndrome, etc.

Small placenta (placental hypoplasia). The placenta is called small if its weight is 2 sigma deviations less than normal, i.e. during a full-term pregnancy, the weight of such a placenta is less than 300 g, and the PPC is more than 1: 7. Macroscopically: it is thinner than normal, it may contain multiple old infarcts. Microscopically: characterized by a predominance of small villi, narrowing of the lumen of the villi vessels, focal or diffuse fibrosis and stromal hyalinosis. A small placenta is observed with gestosis, hypertension, chronic heart and kidney failure in the mother, severe hemolytic anemia of the fetus, trisomies 13 and 18, and maternal smoking. Combined with defects of the placenta and fetus. Extreme degree of placental hypoplasia can cause intrauterine death and fetal underdevelopment.

In the middle of the 19th century. attempts have been made to elucidate the origin of various placental structures; in the 60-70s. XIX century this problem was solved by P. A. Leninsky and T. Langgans, who established the fetal origin of the epithelial cover of the chorion. A distinctive feature of the embryogenesis of placental mammals, including humans, is the early appearance and rapid development of the trophoblast. Already at the first stages of zygote fragmentation and further, at the morula stage, two types of cells are separated and distinguished: superficially located, forming the trophoblast, and internal, darker cells, forming the embryoblast itself. The trophoblast of an embryo that has not yet been implanted, which is the rudimentary material of the chorionic epithelium, performs a trophic function to one degree or another. Implantation is the milestone from which the transformation of the embryonic trophoblast into chorionic epithelium begins, which, together with the extraembryonic mesenchyme, forms the villous chorion.

On the 6-7th day of embryo development, the implantation process begins, in which the trophoblast, penetrating into the uterine mucosa, plays a leading role.

With the help of secreted histolytic enzymes, the trophoblast destroys the tissue of the uterine mucosa in a small adjacent area, while not only the epithelium and connective tissue of the uterus, but also the walls of blood vessels disappear, and thus the embryo is surrounded by maternal blood. Moreover, attachment and invasion of the egg occurs only in the area where a large blood vessel passes through the base of the uterine epithelium, i.e., the choice of the implantation site is determined by the creation of the most favorable conditions for the microenvironment and the transfer of chemicals, especially the removal of carbon dioxide. Starting from the 9-10th day of development, trophoblast reproduction becomes so intense that a new generation of mitotically dividing CTB cells displaces the implantation “plasmodium” and forms the syncytial layer itself. Small cavities (lacunae) appear in the trophoblast, into which the mother’s blood flows due to erosion of small vessels and capillaries. The strands and septa of trophoblast separating the lacunae are called primary villi. With their appearance, the blastocyst is called the amniotic sac.

By the end of the 2nd week of pregnancy (12-13th day of development), connective tissue grows into the primary villi from the chorion side, resulting in the formation of secondary villi.

The basis of these villi is connective tissue, and the outer cover is formed by trophoblast. From the 3rd week of embryo development, the placentation period begins, which is characterized by vascularization of the villi and the transformation of secondary villi into tertiary villi containing vessels. The process of vascularization of the villi is accompanied by a decrease in the growth rate and differentiation of the chorionic epithelium. In early angiogenesis, two main processes are distinguished: 1) differentiation of angioblasts from trophoblasts; 2) connection of angioblasts into dense cords and into the vascular network. Subsequently, angioblastic components grow into the primary villi and their branches. From the 14th to the 20th day, intensive proliferation of the trophoblast is observed, as a result of which blood circulation is finally established in the newly formed lacunar cavities, which together make up the intervillous space.

Vascularization of the villi and the transformation of secondary villi into tertiary ones do not occur simultaneously and evenly over the entire surface of the chorion. Tertiary villi become thicker, and two layers of epithelium are clearly visible in them. The connective tissue stroma of the villi is represented by a colorless mass with a uniform network of delicate collagen fibers and two types of cells.

Among the cellular elements of large villi, fibrocytes predominate; in medium and small villi, histiocytes predominate. The number of Kashchenko-Hofbauer cells (placental macrophages) is quite large, but they are small in size and irregular in shape. The trophoblast basement membrane is adjacent to the villous stroma. Blood capillaries, already formed in many villi, usually pass immediately under the epithelium. When the branches of the umbilical cord vessels connect with the local circulatory network, the circulation of embryonic blood is established in the tertiary villi, which coincides with the beginning of the heartbeat of the embryo (21st day of development). The formation of fetal-placental circulation is an important stage in the morphogenesis of the placenta. Opening of the spiral arteries of the uterus due to the growth of the central tuberculosis into the wall of the vessels of the decidua usually occurs at the end of the 6th week of pregnancy and causes the occurrence of uteroplacental circulation.

Thus, in the middle of the first trimester of antenatal development, the trophoblast with its villi and extraembryonic mesenchyme form the chorion, which is a highly specialized, powerfully developed organ. The surface of the chorion, facing the uterine cavity, loses villi, thus forming a smooth chorion. Differentiation of the chorion into smooth and branched occurs during the first trimester and is associated with different conditions of the blood supply.

Chorionic biopsy or chorionic villus biopsy is one of the modern invasive methods of direct prenatal diagnosis. It is intended for collecting tissue samples of embryonic origin with their subsequent molecular genetic, cytogenetic, and biochemical studies. Chorionic biopsy is performed strictly according to indications and only at certain times of gestation by specialists who have the appropriate certificate and experience.

What is chorion and what does its study provide?

The chorion is the villous extra-embryonic outer membrane. It is formed 7-12 days after conception from the fusion of cells of the extraembryonic mesoderm and trophoblast. And from the end of the first trimester of pregnancy, the chorion gradually transforms into the placenta. At the same time, its tertiary well-vascularized villi form branches and form cotyledons (structural and functional placental units). In this case, direct contact between the maternal and fetal blood circulation finally ceases.

The main functions of the chorion include:

Separation of the embryo from the tissues of the uterine wall. In this case, the chorion with its villous part is in contact with the decidua (formed from the endometrium). And its smooth part is the second layer of that part of the fetal sac, which is called the fetal membrane.
Ensuring the exchange of substances and gases between the embryo and maternal blood (excretory and trophic functions). This is possible due to the growth of chorionic villi into the walls of the spiral arteries of the uterine wall.
Protection of the embryo from infectious agents and toxins. This barrier begins to work fully from the 10th week of gestation, when the formation of the placenta begins. In the early stages of pregnancy, chorionic villi are not yet able to adequately filter substances contained in a woman’s blood. Therefore, this period is characterized by a fairly high probability of occurrence of disorders of embryogenesis of a toxic and infectious nature.

Chorion tissues are of embryonic origin. So their genetic material is basically the same as that of an embryo. And taking a small part of the chorion for research does not affect the process of organogenesis of the unborn child and in 97-99% of cases is not critical for prolonging pregnancy. This is what is used when performing chorionic villus biopsy for a variety of hereditary anomalies.

How informative is chorionic villus biopsy?

Currently, chorionic villus biopsy followed by examination of the resulting material makes it possible to identify almost 3,800 different diseases. Moreover, the result obtained has a high degree of reliability.

The diagnostic capabilities of chorionic biopsy include identifying the following groups of diseases:

Various chromosomal abnormalities (Down, Edwards, Turner, Klinefelter, Patau syndromes, etc.).
Monogenic diseases with different types of inheritance.
Enzymatic pathologies - for example, phenylketonuria, Lesch-Nyhan syndrome, citrulinemia, arginine succinic aciduria.
Thalassemia and other hemoglobinopathies.
Numerous lysosomal storage diseases. These include sphingolipidoses (Fabry, Crabbe, Landing, Tay-Sachs, Niemann-Pick diseases, adrenoleukodystrophy, etc.), carbohydrate metabolism disorders (glycogen storage diseases, Pompe disease), glycosaminoglycan metabolism disorders (various mucopolysaccharidoses), and glycoprotein metabolism disorders.

The reliability of identifying these diseases is very high. Diagnostic errors may be associated with technical errors when collecting material, when uterine tissue is also included in the chorionic villus biopsy. But this is rare. False-positive test results for mosaicism are also possible, when this chromosomal pathology occurs only in chorion cells.

Diagnostic errors occur in no more than 4% of cases. Moreover, they are usually associated with overdiagnosis, rather than false negative results. So the method as a whole has high accuracy. But it also has some limitations. For example, a chorionic villus biopsy will be uninformative if the embryo has defects in the formation of the neural tube that are not associated with pathology of the genetic material.

Of course, the diagnostic capabilities of the method depend on the technical equipment of the medical genetic center and the availability of certain reagents in it. Therefore, if a certain uncommon anomaly is suspected, the doctor must first clarify whether the necessary research can be carried out in this laboratory. If necessary, the material is sent to another region in compliance with the necessary transportation conditions.

In what cases is research carried out?

Chorionic villus biopsy is not an ordinary test. It is carried out only if there are certain indications, if non-invasive diagnostic methods do not provide the necessary and reliable information. The decision on such manipulation is usually made by a medical commission and requires the mandatory informed consent of the woman. She has the right to refuse the proposed diagnosis, which is not the basis for any subsequent restrictions on the scope of the prescribed examination and treatment.

Indications for chorionic villus biopsy include:

Previous birth of a woman with a child with disorders caused by any gene or chromosomal abnormalities. The fact of stillbirth or death of a newborn in the first few days is also taken into account.
The presence of people in the family with hereditary diseases, even if they are not first-degree relatives. Confirmed carriage of a recessive pathological gene (including sex-linked) in at least one of the parents.
An unfavorable result of the first mandatory prenatal screening (ultrasound and biochemical examination) with an identified high risk of certain chromosomal diseases in the embryo.

A relative indication is also the age of a woman over 35 years old. After all, this is associated with an increased likelihood of spontaneous critical mutations, especially in the presence of other factors predisposing to this.

Contraindications

A planned chorionic villus sampling may be delayed or canceled in the following cases:

high risk of threatened miscarriage - for example, with multiple myomatosis or the presence of a large fibroid node with significant deformation of the uterine cavity;
already diagnosed threatened abortion (high uterine tone, appearance of bloody discharge from the genital tract);
the woman has fever, a current acute infection or a clinically significant exacerbation of a chronic infectious and inflammatory disease;
features of the attachment of the chorion, which leads to its inaccessibility for biopsy;
dermatitis or infectious lesion of the skin and subcutaneous tissue on the anterior abdominal wall diagnosed in a woman (with a planned transabdominal chorionic villus biopsy);
infectious nature (in the case of transcervical chorionic biopsy);
clinically significant deterioration in the general somatic condition of the pregnant woman.

Time frame for the study

The timing of chorionic villus biopsy is determined by the period when the embryo’s main organs and systems are already formed, its membranes are quite large, but the placenta has not yet fully formed. Therefore, the procedure is most often performed between 10 and 13 weeks of gestation.

In addition, during this period the risk of biopsy-provoked spontaneous abortions is significantly lower than in earlier periods. And the doctor usually already has the result of the first basic prenatal screening, which provides indicative information about the presence of signs of some of the most common chromosomal diseases.

At later stages, the chorion is gradually transformed into the placenta. Taking a sample (part) of this formation is also possible. But this is a different test called placentocentesis or placental biopsy.

A combination of several techniques is also possible. For example, sometimes chorionic villus biopsy is performed using one access (simultaneously). This makes it possible to significantly increase the information content and reliability of prenatal diagnosis, as it also makes it possible to obtain information about abnormal development of the fetus or its infection.

Types of research

Currently, 2 types of chorionic biopsy are practiced:

Transabdominal, when access to the uterine cavity and fetal membranes is achieved by puncturing the anterior abdominal wall.
Transcervical - through the cervical canal, without violating the integrity of the uterine wall.

Transabdominal chorionic villus biopsy can be single-needle or double-needle.

Currently, the transabdominal technique is most often preferred. In this case, the specialist gains access to the chorion located along the front or side walls at any level. But when attaching the embryo along the posterior surface of the uterus, it is advisable to use the transcervical technique.

How is chorionic villus sampling performed?

Before the procedure, the woman is given a preliminary examination. It includes general clinical blood and urine tests, analysis for major infections, and a vaginal smear to determine the degree of purity. The procedure is also mandatory despite the first screening being recently carried out. Often, sonography is performed on the day of the biopsy. In fact, the specialist first assesses the condition of the uterus and the position of the embryo, after which he begins the procedure for collecting biomaterial.

Although chorionic villus sampling is an invasive procedure, it is performed in the vast majority of cases without the use of anesthesia. In the case of the transabdominal technique, application anesthesia can be used, if necessary, to reduce discomfort at the time of skin puncture.

Chorionic villus biopsy is performed under mandatory ultrasound control of the position of the puncture needle. In this case, the free-hand method or a special puncture adapter can be used. 1-2 hours before the examination, the woman is recommended to drink several glasses of water, which will fill the bladder and thereby significantly improve visualization of the uterine cavity.

In general, the procedure (for the transabdominal option) includes:

Antiseptic treatment of the area on the abdomen that is supposed to be used for puncture.
Linear puncture of the tissues of the anterior abdominal wall and uterus with immersion of the tip of the puncture needle into the myometrium.
Changing the position of the needle so that it is directed parallel to the chorionic membrane.
Immersion of the needle into the chorionic tissue, removal of the mandrin and gentle aspiration of the sample. In this case, to collect the material, a syringe with a transport medium is attached to the outer contour of the needle. If a two-needle technique is used, only the inner needle of a smaller diameter is immersed into the chorion. A thicker guide needle acts as a trocar for the initial puncture of the abdominal wall and uterine wall.
Removing the needle, covering the puncture site with an aseptic bandage, ultrasound monitoring of the embryo's heartbeat and the condition of the uterine wall.

During transvaginal chorionic biopsy, material is collected using a flexible thin catheter with a mandrel. In this case, the cervix is fixed by grasping it with bullet forceps. The tip of the catheter is also inserted into the chorion parallel to the uterine wall under ultrasound guidance.

Usually the entire procedure takes no more than 30 minutes. Although, when the chorion is located on the side walls of the uterus or in its corners, technical difficulties with access are possible, which will increase the duration of the biopsy.

For a full diagnosis, it is necessary to obtain at least 5 mg of chorionic tissue. The optimal biopsy volume is 10-15 mg. This will allow you to conduct several types of research if necessary.

Possible risks of the procedure

The invasiveness of this technique is the main risk factor for the development of possible complications and consequences. True, they occur infrequently and are not always associated with technical errors in the biopsy performed or insufficient experience of the doctor. In general, according to medical statistics, no more than 4-5% of patients experience serious complications.

It is also worth paying attention to a couple of nuances. The first concerns expectant mothers.

Patients with negative Rh factor blood are required to buy a capsule with anti-Rh immunoglobulin before the procedure.

It should be administered no later than 48 hours after the procedure. In some cases, this is done immediately in the clinic.

HIV-infected women will have to undergo more intensive antiretroviral therapy due to the risk of contracting this infection to the fetus.

Technique

There are two ways to perform the CVS procedure – transabdominal and transcervical. In the first method, they enter the uterus through a puncture in the abdominal cavity. In the second - through the cervix.

Important! The transcervical method is absolutely contraindicated for women who suffer from the presence of pathogenic microflora in the vagina of III – IV degree of purity.

The choice is made by the doctor according to medical indicators. Both methods involve the use of an ultrasound machine, which allows the doctor to control the movement of the needle, the amount of tissue taken for analysis and possible risks. Without this device, BWH would be impossible.

BVS - transabdominal method

The procedure is similar to simple surgery. The woman lies down on the operating table, then she is given an injection of local anesthetic in the place where the puncture will be made. Using a needle, they carefully penetrate the abdominal wall, the walls of the myometrium, and finally reach the chorion. The needle must be placed parallel to the sheath to avoid damage to it.

Using a syringe with a nutrient medium, the doctor captures the required amount of chorionic villi tissue (at least 5 mg) and removes the syringe.

During an abdominal piercing, a woman may experience slight cramps that will resemble menstrual cramps.

Externally, the manipulation is similar to a simple examination by a gynecologist. The patient is positioned on a gynecological chair, the vaginal walls and cervix are fixed with special forceps, and chorionic tissue is penetrated using a catheter. Then a syringe is attached to the catheter, after which material for analysis is collected in the same way.

When tissue is collected through the cervix, it will resemble a regular smear test.

Chorionic villus biopsy for multiple pregnancies

Chorionic biopsy during multiple pregnancy requires the professionalism of the doctor performing the procedure. If we talk only about the technical side of the issue, it can be noted that in order to accurately determine the karyotype of each fetus, chorionic villi must be taken from each fetal receptacle. This is often necessary to prevent so-called conflict situations during pregnancy, when one embryo interferes with the development of another.

How to behave after the procedure?

After the CVS procedure, the patient should be completely at rest. Usually the woman is sent home with a strong recommendation to rest both physically and mentally.

Working mothers are advised to take a day off. For 1–2 days, it is strictly forbidden to lift anything heavy, as well as to have sex. In addition, the patient should monitor her sensations and vaginal discharge.

Small cramps that become weaker over time are normal. If the intensity of spasms and pain increases, you should immediately consult a doctor.

Also a reason to contact an antenatal clinic is excessive watery or bloody vaginal discharge. These are signs of spontaneous termination of pregnancy, in other words, miscarriage.

results

A full analysis will be ready no earlier than in 10–14 days.

The material obtained during the procedure is tested using different cultures of colonial bacteria. Each of them reacts to mutations in the cells of the villi.

It takes two weeks to conduct a thorough check. Such an analysis gives the right to claim that the result is 99% accurate.

It is possible to find out preliminary results in just a few days. The so-called FISH method is slightly inferior in accuracy to the traditional one.

Moreover, it is carried out only for an additional fee. Moreover, in each laboratory, in any case, the analysis will be carried out in parallel using the traditional method.

To obtain the most accurate result, the material taken from the patient must undergo some aging. Therefore, the traditional method is preferable.

Reliability of the analysis

The accuracy of the analysis results is 99%. The remaining percentage is given to the possibility of error due to probable mosaicism. If the doctor suspects a similar pathology in the patient, she will definitely be referred to undergo another invasive procedure - amniocentesis or cordocentesis. But already at a later stage of pregnancy.

In addition, the human factor or chance should not be completely excluded. For example, it happens that during a procedure the doctor does not take enough tissue to carry out a full analysis.

It is also quite rare, but it happens that chorion tissue cannot be cultured. In such cases, the patient is referred for a repeat chorionic villus biopsy.

In some laboratories, errors are possible that are based on human error. Or such phenomena as contamination of the biopsy material with maternal cells (this is when the analysis reflects only the state of the placenta in the place where the material was taken, and not the condition of the fetus). That is why you should pay attention to the equipment and newness of the equipment in the clinic where you are going to undergo the procedure.

If there is any doubt about the reliability of the BCV analysis, the patient is prescribed amniocentesis. Statistics say that in most cases the results of the studies are identical. The percentage of errors is small.

Risks and consequences

Before carrying out the procedure, the expectant mother must weigh the pros and cons and take into account all the risks. Lack of information gives rise to speculation, and awareness allows you to prepare for possible consequences.

The risk of miscarriage after chorionic villus sampling is 1–2%.

All other risks are directly related to the professionalism of the medical staff. Puncture of natural barriers with a needle certainly entails rupture of capillaries. As a result, a retrochorial hematoma may form. It can again lead to miscarriage.

The risk of intrauterine infection is 0.1–0.5%. Let us remind you that this incident threatens the life of not only the child, but also the mother.

Statistics of early biopsy complications

The percentage of miscarriages after the transabdominal puncture method is 0.5–1.5%, while after the transcervical analysis it is almost 7.5%.
There may be slight bleeding from the puncture site.
Wall hematomas may form, which provoke detachment of the fertilized egg.
There is a risk of intrauterine infection.

Statistics of late complications of BVC

Sometimes premature birth occurs.
The baby may be light in weight.

Is it necessary to carry out analysis?

Chorionic villus sampling is not one of the tests that the doctor will insist on performing. Worry in this case is justified, since there is a risk of miscarriage. But the totality of medical indications for the procedure is so great that it outweighs the fears.

What are the consequences of refusal?

If a woman refuses to undergo the procedure, she will experience permanent stress throughout the entire period of pregnancy, which can cause miscarriage or fetal death.

Chorionic villus biopsy is necessary not only to decide whether to terminate a pregnancy or use some kind of intrauterine treatment, but also to prepare for childbirth. If this procedure is not carried out, justified by medical indicators, then:

there is a risk of having a child with pathologies that the doctor will not know about;
the maternity ward may not have the necessary equipment or intensive care for newborns if complications suddenly arise during childbirth;
Without knowing what to prepare for, parents can suffer severe psychological trauma after the birth of a child with developmental disabilities.

Where can I get tested, cost and reviews

Pricing policy is not something you should pay attention to when choosing a clinic for undergoing a CVS procedure. The expectant mother should study the statistics of the medical institution, especially the point about the percentage of miscarriages after a biopsy. In addition, it is worth assessing the professionalism of the clinic’s medical staff.

The approximate cost of a chorionic villus biopsy varies from 6,000 rubles to 27,000 rubles.

As for the reviews. There are both positive and negative. And subjective factors are largely to blame for this. It all depends on the qualifications of the doctor performing the manipulation. And also from a woman’s pain threshold. Therefore, it will still be more reliable to focus on dry statistics.

Invasive methods of prenatal diagnosis (video)

Any diagnostics can be carried out only after you give your consent to it. Although CVS is an invasive method, the percentage of complications after sampling is very small. Especially if you compare the degree of risk with the possibility of obtaining accurate results about the condition and development of the fetus already in the early stages of pregnancy. So you should not refuse the test if it is prescribed to you for medical reasons. Just be very responsible when choosing the clinic where you will take it.

Chorionic villus biopsy is a special medical test performed between the tenth and twelfth weeks of pregnancy (the exact period of the “interesting position” is determined by ultrasound). With its help, you can find out the most complete information about the state of the embryo at the moment.

Procedure Fetal Condition Analysis
pregnant woman discomfort on the monitor
new life baby pregnancy

Approximately by the 16th week of the “interesting position,” the chorion is completely transformed into the placenta. But even before the 19th week, you can do a chorionic villus biopsy of the tissues that are needed for the study (it happens that for certain reasons the test was not carried out at the ideal time). But the material will be taken from the placenta, and not from the chorion.

During a biopsy, cells located in the outer membrane of the fetus, adjacent directly to the uterus, are selected. This membrane is entirely covered with villi and is called chorion.

One of the significant disadvantages of the procedure is the price of this procedure. But, as they say, this is not the time to save money.

Determination of fetal health status

Why is this procedure necessary:

to find out whether the growing embryo has any abnormalities or whether there is any cause for concern;
Using this procedure, many diseases are diagnosed, including hereditary ones (for example, hemophilia);
analysis of chorionic villus biopsy with a very high, almost 100% probability allows you to identify various defects in the fetus that arise due to chromosomal abnormalities (the most famous and common such defect is Down syndrome);
Based on the test results, the woman has time to weigh the pros and cons and make a final decision: to continue her pregnancy or not (if she learns about possible risks and abnormalities of the embryo).

Indications for use

Indications for the procedure are as follows.

Chorionic villus sampling is highly recommended for pregnant women who have already celebrated their 35th birthday. This is due to the fact that there is a direct relationship between the frequency of congenital defects and the woman’s age. The older the expectant mother, the correspondingly higher the risk.
The woman already had a pregnancy, which resulted in a child with congenital defects.
The expectant mother has ever previously had a spontaneous miscarriage or a stillbirth.
The medical record indicates that the expectant mother has ever complained of a prolonged absence of menstruation (more than 6 months a year).
The results of the first ultrasound, mandatory for all expectant mothers, which is carried out from the 12th to the 14th week of pregnancy, showed that the fetus is predisposed to developmental abnormalities.
The parents were unable to conceive a child on their own for a long time, as a result of which they were diagnosed with primary infertility.
The parents are blood relatives (the risk of pathologies in the fetus is high, a chorionic villus biopsy is required).
One or both parents have a genetic disorder. The test will determine whether these disorders are passed on to the fetus.
It is necessary to determine the sex of the unborn baby (some genetic diseases are typical only for boys, for example, hemophilia of any type).
Unaware of the pregnancy, the woman took an x-ray.
At an early stage of the “interesting situation,” the woman took medications that had a negative effect on the nascent life. In this case, a chorionic villus sampling performed at 10, 11 or 12 weeks usually shows that the risk of birth defects in the fetus is extremely high.
At the time when conception had already occurred, the expectant mother was affected by unfavorable factors. For example, she could have been in an area with a high radioactive background or inhaled harmful substances.

Methods for performing the procedure

How a chorionic villus biopsy is performed during pregnancy, see photos and descriptions below.

There are different reviews about chorionic villus biopsy. The overwhelming majority of women note that this procedure is painless, although not pleasant: both physically and psychologically.

Mostly those who had it done on time, but the results were not confirmed or were not reliable enough, speak negatively about chorionic villus biopsy. This is extremely rare, but it happens, because the achievements of modern medicine are not 100% perfect.

Medical personnel usually report the results of a chorionic villus biopsy with an identified risk of Down syndrome in the fetus as quickly as possible, literally as soon as they become known. Conversely, the absence of news in this case is good news.

Risks and possible dangers

A test to identify possible developmental anomalies in the fetus is, of course, an important procedure, but, unfortunately, it is not absolutely safe for both the fetus and the pregnant woman herself. After a chorionic villus biopsy, complications for the expectant mother and/or the pregnant fetus are possible.

Analysis for the presence of pathologies

Risk for the expectant mother: during the test, an infection may enter the uterine cavity.

Risks to the fetus:

threat of miscarriage caused by detachment of the ovum;
the child may be born with low body weight (up to 2.5 kg);
the baby may be born ahead of schedule.

The above risks are practically reduced to zero if the procedure is carried out by a highly qualified and experienced specialist.

Many women wonder: should they do a chorionic villus biopsy or amniocentesis, in which amniotic fluid is taken for analysis? It is worth noting that the danger to the mother and embryo in both cases will be approximately the same. The reliability of both tests is also no different.

However, amniocentesis is performed at a different time: from the 15th to the 20th week of the “interesting situation” (biopsy from the 10th to 12th week). If a decision is made to terminate the pregnancy, then at 20-22 weeks the risk of possible complications from an abortion for a woman is lower, which is a definite plus for choosing a biopsy.

It is not recommended to perform a transcervical chorionic villus biopsy in the presence of one or more deciduidal polyps; it is also not worth removing polyps - this poses a risk of miscarriage and can also cause premature birth.

Contraindications for the procedure are also:

risk of miscarriage;
inflammatory diseases of the female organs or abdominal skin (depending on the type of biopsy performed);
HIV infection of an expectant mother is not a reason to refuse the test, but since the likelihood of transmission of infection from mother to fetus increases, the woman is prescribed an increased dose of antiretroviral drugs.

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Expectant mothers are usually scared when doctors recommend that they undergo a chorionic villus sampling. This procedure is not a mandatory examination during pregnancy, but sometimes it becomes necessary. Let's look at what a chorionic villus biopsy is, and also get acquainted with the indications and methods for performing it.

What is chorionic villus sampling?

A chorionic villus biopsy is a test that removes a small sample of chorionic villi—protrusions of the placenta that contain the same chromosomal material as the fetus. By studying this tissue sample, you can find out the chromosomal composition of the baby's cell nuclei without affecting the baby himself. Carrying out a chorionic villus biopsy makes it possible to diagnose many congenital malformations: Down syndrome, cystic fibrosis, Turner syndrome, Edwards syndrome, sickle cell anemia, Klinefelter syndrome and more than a hundred rare chromosomal pathologies. In addition, it is used to determine many hereditary diseases, such as hemophilia and amaurotic idiocy.

Chorionic villus biopsy is not a completely safe diagnostic procedure. According to medical statistics, one out of a hundred pregnant women will have a miscarriage after this intervention. In addition, such a test is expensive, so many expectant mothers, with the help of a doctor, choose an alternative test.

Chorionic villus biopsy: indications for performing

There are certain indications for chorionic villus biopsy:

The pregnant woman is over 35 years old. The older the expectant mother, the greater the risk of her child developing Down syndrome and other chromosomal pathologies;
Questionable results of prenatal screening. If, after a woman’s blood test or an ultrasound scan of the fetus, a high probability of having a baby with a genetic or chromosomal abnormality is determined, doctors often prescribe a chorionic villus biopsy;
The need to determine the sex of the unborn child. It usually occurs when one of the parents is a carrier of a disease that causes abnormalities in the development of the fetus (hemophilia, Duchenne muscular dystrophy, etc.);
The family already has a child with a defect at the chromosomal level.

How is a chorionic villus biopsy performed?

Doctors call the ideal period for performing a chorionic villus biopsy 11-13 weeks of pregnancy. During this period, the research results are the most reliable. Before the procedure, the pregnant woman must undergo some examinations. First of all, to confirm the number of fetuses and anomalies in their development, the woman is sent for an ultrasound of the pelvic organs. It is also necessary to determine the blood type and Rh factor. Sometimes, if Rh is negative, it is necessary to administer a special medicine after a biopsy.

In some cases, the timing for chorionic villus biopsy is slightly delayed. So, if necessary, the study is carried out at 10-19 weeks of pregnancy. In any case, only a doctor can determine its feasibility and time of implementation.

So, how is a chorionic villus sampling done? Depending on the location of the placenta, the doctor may perform manipulations through the cervix (transcervical biopsy) or the skin of the abdomen (abdominal chorionic villus sampling).

During abdominal chorion biopsy, the skin of the abdomen is wiped with an alcohol or iodine solution, then local anesthesia is applied and a thin long needle is inserted into the abdominal cavity, which enters the placenta and takes a piece of tissue for analysis.

When performing a transcervical biopsy, the doctor first treats the vagina and cervix with an antiseptic, after which he inserts a probe into the placenta and takes a small sample of its tissue for examination.

Both types of biopsies are performed using ultrasound. This is necessary for precise guidance of the needle or probe.

Upon completion of the manipulations, the tissue sample is sent to the laboratory, where it is placed in a special environment that promotes cell division. After some time, the cells are broken down with a special enzyme and analyzed for genetic and chromosomal abnormalities.

What happens after the procedure?

After a chorionic villus biopsy, a pregnant woman should spend the rest of the day in absolute peace at home, avoiding even minor physical activity. Within 1-2 days she may experience slight cramps in the abdominal area, which is quite normal. In the next 2-3 days after the biopsy, you should not lift heavy objects, have an intimate life, and you should avoid air travel.

It is necessary to urgently call a doctor if, in the first days after a chorionic villus biopsy:

Painful abdominal cramps intensified;
There is profuse bloody or watery vaginal discharge.

The results of the study are usually ready 7-10 days after sending the tissue sample to the laboratory. Preliminary results can be found out in 2-3 days. A negative result will confirm that the fetus does not have developmental defects at the gene and chromosomal level. However, it is important to consider: such a conclusion is not a guarantee that the child will be born completely healthy. 4.8 out of 5 (24 votes)