Chorionic biopsy: when it is carried out, preparation and course of the procedure, the result. Chorionic biopsy: the essence and features of this examination
An invasive procedure, which consists in obtaining chorionic villi for subsequent research in order to diagnose congenital and hereditary diseases of the fetus.
Synonyms: Chorionic villus sampling, chorionic villus aspiration.
Classification
- By access technique:
- transabdominal;
- transcervical
- According to the technique of execution (transabdominal chorinbiopsy):
- single-needle;
- two-needle
Indications
- Pregnant age 35 years and older
- The presence in the family of a child or the identification in previous pregnancies of a fetus with Down syndrome or other chromosomal diseases
- The presence in the family of a child with multiple congenital malformations
- Parental karyotype abnormalities
- The presence of biochemical and / or ultrasound markers of chromosomal diseases or congenital malformations in the fetus.
- Determination of the sex of the fetus in the presence of X-linked gene diseases
Relative contraindications
- Acute inflammatory process or exacerbation of a chronic inflammatory process of any localization
- The presence of clinical and / or ultrasound signs of threatening or incipient abortion
Preparation for research
Before chorionic biopsy, an ultrasound scan is performed to clarify the gestational age, the presence of fetal heartbeat, the localization of the chorion, the length of the cervical canal, and the state of uterine tone. Perform standard processing of the operating field.
Pain relief methods
In most cases, it is performed without anesthesia.
Operation technique
Chorionic biopsy is performed at 10-12 weeks of pregnancy. Moderate bladder filling is required for optimal imaging.
Chorionic villus sampling can be done by transcervical or transabdominal access. The choice of access is determined by the attending physician, taking into account the localization of the chorion.
Transabdominal biopsy preferable. It is produced by the free hand method or using a puncture adapter. The use of the puncture adapter is preferable, since it allows you to select the trajectory of the puncture needle movement using the trace on the monitor screen and control the depth of its immersion.
There are two techniques for trasabdominal chorionic villus sampling: one-needle and two-needle.
The single-needle method consists in sequential puncture of the abdominal wall, uterine wall, and chorionic tissue with a standard 20G needle.
Two-needle method: using a guide needle (16-18G diameter) and a smaller diameter internal biopsy needle (20G).
In the single-needle technique, the needle is guided into the chorionic tissue, positioning it parallel to the chorionic sheath. After the needle crosses the myometrium, it is guided parallel to its inner contour. As with transcervical biopsy, the needle should be immersed in the chorionic tissue while remaining parallel to the chorionic sheath. After making sure with the help of ultrasound in the correct position of the needle, the mandrel is removed from it and a syringe with 5 ml of transport medium is attached. Removing the needle is also accompanied by an aspiration process. In the absence of conditions for transabdominal access, a transcervical biopsy is performed.
Transcervical biopsy it is preferable when the chorion is located on the posterior wall of the uterus. The manipulation is carried out while the patient is in the gynecological chair. Sometimes, to change the position of the uterus, its cervix is fixed with bullet forceps. For transcervical access, a polyethylene catheter is used, inside which a flexible mandrel is placed, obturating its lumen and providing it with the necessary strength. The proximal end of the catheter has an adapter that allows it to be connected to conventional Luer-type syringes. The catheter is sequentially advanced through the cervical canal, the internal pharynx, then directed between the chorionic membrane and the wall of the uterus, into the chorionic tissue. The mandrain is removed from the lumen of the catheter, a 20 ml syringe containing about 5 ml of culture medium is attached to it. Due to the negative pressure created in the syringe, villi are aspirated, gradually removing the catheter from the chorionic tissue.
In the two-needle technique, a needle of a larger diameter (outer) is used as a trocar, which is inserted into the myometrium, and a thinner and longer (inner) needle is immersed directly into the thickness of the chorion. Then the mandrel is removed from it and the syringe is attached. Further, aspiration is carried out in the same way as in the one-needle technique.
Most genetic studies require at least 5 mg of chorionic tissue. If not enough material is received on the first attempt, the procedure can be repeated without additional risk. The risk of termination of pregnancy will significantly increase after the third attempt.
The reason for false-positive and false-negative results of a laboratory study of a biopsy specimen can be: contamination of the material with mother cells, as well as the presence of mosaicism limited to the placenta, which occurs in 1% of studies. When placental mosaicism is detected, an additional cordocentesis is recommended to clarify the diagnosis.
Information for the patient Before the procedure, the patient is informed about the indications, the technique of performing, the possible risk of chorion biopsy, and informed consent is obtained for its implementation.
Complications
Bloody discharge from the genital tract
After transcervical chorionic biopsy, they are found in every third patient. In most cases, spotting stops on its own without affecting the outcome of pregnancy. In 4% of cases, after a biopsy, a retrochorial hematoma may form, which usually resolves before the 16th week of pregnancy. With transabdominal access, bleeding from the genital tract after surgery occurs in isolated cases.
Infectious complications
The risk of developing chorioamnionitis does not differ from the population risk and is about 0.3%.
Violation of the integrity of the membranes
A rare complication (in 0.3% of cases), more common with transcervical chorionic biopsy.
Increase in the level of α-fetoprotein in the serum of a pregnant woman
It is transient in nature, returns to physiological values by the 16-18th week, which makes it possible to carry out biochemical screening of congenital and hereditary diseases of the fetus in pregnant women during these periods.
Development of alloimmune cytopenia in the fetus
After performing chorionic biopsy, prophylactic intramuscular administration of anti-RhO (D) immunoglobulin is recommended for 48-72 hours (depending on the drug used) to Rh-negative non-sensitized pregnant women with a Rh-positive partner:
- if the test result is received later than 48-72 hours after the procedure;
- if the chorionic biopsy results indicate an Rh-positive fetus
Abortion
In specialized centers, the frequency of spontaneous abortions, premature birth after chorionic biopsy is about 2-3%, which corresponds to the general population level.
Features of postoperative management
Conservation therapy, intraoperative antibiotic prophylaxis and / or therapy (if indicated) are performed.
An 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 disorders
Rice. 4.38. Chorionic biopsy (transcervical access).
metabolism), determining the sex of the fetus. Sampling is carried out trans-cervically or transabdominally in the period from 8 to 12 weeks of pregnancy under the control of ultrasound (Fig. 4.38). A sterile polyethylene flexible catheter (26 cm long and 1.5 mm outer diameter) is inserted into the uterine cavity and carefully, under visual control, it is advanced to the placenta localization and further between the uterine wall and the placental tissue. Then, with a syringe with a capacity of up to 20 ml, containing 3-4 ml of nutrient medium and heparin, the chorionic tissue is aspirated, which is further examined. Chorionic tissue sampling is also possible in cases of bichorionic twins.
Complications of chorionic villus biopsy can be intrauterine infection, bleeding, spontaneous miscarriages, and the formation of hematomas. Later complications include premature birth, low birth weight (less than 2500 g), fetal malformations. Perinatal mortality reaches 0.2-0.9%.
Contraindications to a chorionic biopsy may be the presence of an infection of the genital tract and symptoms of a threatening miscarriage.
Fetoscopy
Fetoscopy- direct examination of the fetus - used to identify congenital and hereditary pathology. The method allows you to examine parts of the fetus through a thin endoscope inserted into the amniotic cavity, and through a special channel to take samples of blood and epidermis for analysis. Fetoscopy is performed as the final stage of genetic examination if a congenital fetal anomaly is suspected.
Method of inserting a fetoscope: after appropriate skin treatment under local anesthesia under sterile conditions, a small skin incision is made and the trocar located in the cannula is inserted into the uterine cavity. Then the trocar is removed, a sample of amniotic fluid is obtained for examination, and an endoscope is inserted into the cannula. If necessary, the depth of insertion of the endoscope can be determined using an ultrasound probe. Upon reaching the placenta, the doctor can examine the vessels of the placenta and take blood from the vessels of the umbilical cord; if it is not possible to obtain fetal blood samples, an aspirate from the placenta can be taken. Due to the official nature of the endoscope's field of view, it is usually impossible to examine the entire fetus in one procedure. In this regard, it is recommended to carry out a targeted examination of any part of the fetus. If necessary, after examining the fetus with special forceps, a biopsy of the desired skin area is performed. At the end of the operation, the instruments are removed from the uterus, cardiac monitoring of the fetus is carried out and the monitoring of the pregnant woman for 24 hours.
Complications of fetoscopy include rupture of amniotic fluid, termination of pregnancy. Complications such as bleeding and the development of infection, the formation of small superficial hematomas on the limbs of the fetus are extremely rare. Due to the possibility of abortion, fetoscopy is rarely used.
4.3.13. Hormonal profile research
Biological methods for diagnosing pregnancy. Among the most common biological reactions to pregnancy are the hormonal reaction of Friedman, Ashheim - Tsondek, the hormonal reaction on frogs (the Galli - Mainini reaction).
Friedman's reaction. The woman's urine is injected into the ear vein of the rabbit. If the urine contains hCG, then 12 hours after the introduction of urine, the rabbit ovulates.
Galli - Mainini reaction. Based on the ability of male frogs to secrete sperm into the ejaculatory ducts under the influence of hCG contained in the urine of pregnant women.
Ashheim test - Tsondeka. After injection of urine of a pregnant woman, which contains CG, infantile female mice weighing 6-8 g in their ovaries observe hemorrhages in the follicles and the formation of a corpus luteum.
Currently, biological methods for diagnosing pregnancy have lost their leading role and preference is given to immunological methods.
Immunological methods for diagnosing pregnancy. TO immunological methods include various methods for determining in serum and urine of chorionic gonadotropin (CG) or its p-subunit (p-HG). Preference is given to the radioimmunoassay method for the quantitative determination of r-hCG in blood serum, since it has a high specificity and sensitivity. Immunoassay methods for detecting hCG in urine, as well as other variants of immunological tests (capillary, plate), deserved a positive assessment. Have the right to
the existence of such well-known serological methods for the determination of CG in urine, such as the reaction of inhibition of agglutination of erythrocytes or sedimentation of latex particles.
All laboratory methods for diagnosing pregnancy are highly specific: the correct answers are observed in 92-100% of cases from the 9-12th day after fertilization of the egg. However, these methods make it possible to establish only the fact of the existence of pregnancy without specifying its localization, therefore, they cannot be used for the differential diagnosis of uterine and ectopic pregnancy.
Agglutination, or latex particle fixation test, is a method for determining the level of hCG in urine. CG is excreted in the urine as early as 8 days after fertilization. A few drops of the patient's urine are mixed with AT and HCG, then latex particles coated with HCG are added to this mixture. If hCG is present in urine, it binds to AT; if CG is absent, then AT binds to latex particles. This rapid test is positive in 95% of cases from the 28th day after fertilization.
Radioimmunoassay test. The test material is blood. Determine the quantitative content (3-subunits of hCG in blood plasma.
Radiological method. Examine the blood. Determine the number (3-subunits of CG, competing with labeled CG for binding to receptors of CG cells of the corpus luteum of the cow. This rapid test is quite sensitive, but not as specific as the radioimmunoassay test.
Methods for assessing the state of the placenta and fetus. V During pregnancy, to assess the function of the placenta and the state of the fetus, the following hormones are determined: chorionic gonadotropin (CG), placental lactogen (PL), progesterone, estrogens, prolactin, dehydro-epiandrosterone sulfate (DHEAS), thyroid hormones and cortico-steroids.
The following methods are used to determine the level of hormones:
Single urine test;
Analysis of daily urine (compensating for daily fluctuations in secretion
tion of hormones);
Blood test of a pregnant woman;
Determination of the content of hormones in the amniotic fluid.
Currently, the content of most hormones in biological fluids is determined by radioimmunoassay. The content of hCG in blood and urine can be determined by biological, immunological and radiological methods. Immunological (including radioimmunological) tests have higher specificity and sensitivity than biological methods.
Knowledge of normal hormone levels (see. Physiology of pregnancy) it is necessary to identify the pathology of pregnancy and the degree of risk of complications for the fetus. In this case, it is necessary to take into account the daily fluctuations in the level of hormones. Deficiency of a number of hormones necessary for the normal course of pregnancy can be corrected by their exogenous administration.
PREGNANCY MANAGEMENT
Our Center carries out
In case of normal or pathologically proceeding pregnancy, the Center performs:
1. Ultrasound examination of the fetus - at 10-11 weeks, 20-21 weeks, 30-31 weeks;
2. Diagnostics and prevention of the birth of children with chromosomal diseases (including Down's syndrome) and developmental defects
- ultrasound examination of the fetus in order to identify ultrasound markers of chromosomal diseases - at 10-11 weeks;
- analysis of levels of serum markers - β-hCG and PAPP-A; as well as 17 oxyprogesterone with the calculation of the individual risk of Down syndrome and adrenogenital syndrome in the fetus - at 11-14 weeks
- analysis of the levels of serum markers - β-hCG, AFP, 17-OH, conjugated estriol with the calculation of the risk of Down syndrome and adrenogenital syndrome in the fetus - at 16-18 weeks
- chorionic villus aspiration - at 11-13 weeks
- cordocentesis - at 20-22 weeks.
4. Diagnosis of intrauterine infection of the fetus
- amniocentesis with bacteriological examination of amniotic fluid (for the diagnosis of bacterial infections)
- ELISA and PCR of the blood of a pregnant woman + ultrasound of the fetus + cordocetez or amniocentesis (for the diagnosis of intracellular infections).
6. Invasive fetal treatment
- puncture of the pyelocaliceal system with obstructive uropathy
- puncture of pathological fluid accumulations in various cavities
8. Removal of excess amniotic fluid with polyhydramnios
9. The introduction of artificial amniotic fluid with oligohydramnios
10. Determination of the sex of the fetus
11. Establishing biological paternity
Diagnostics of monogenic diseases and DNA diagnostics
In the presence of monogenic diseases in parents who are transmitted by a recessive or dominant mode of inheritance, their prenatal diagnosis is performed. The blood of parents and fetal material (chorionic villi, placental tissue, umbilical cord blood, amniotic fluid) are examined for the following monogenic diseases:
- adrenogenital syndrome
- cystic fibrosis
- phenylketonuria
- congenital hypothyroidism
- polycystic kidney disease
- ataxia telangiectasia (Louis-Bar syndrome)
- Friedreich's ataxia
- achondroplasia
- Wilson-Konovalov disease
- Norrie's disease
- Unferricht-Ludborg disease
- Stadgart's disease
- hemophilia type A, B
- lipodystrophy
- dilated cardiomyopathy type 1A
- methemoglobinemia
- myotonic dystrophy
- lumbar-limb muscular dystrophy, type 2A
- Emery-Dreyfus muscular dystrophy
- violation of sex determination
- hereditary motor-sensory neuropathy (Charcot-Marie-Tooth disease)
- hereditary neuropathy with susceptibility to compression paralysis
- sensorineural non-syndromic hearing loss
- oculopharyngeal myodystrophy
- recessive osteoporosis
- periodic illness
- progressive muscular dystrophy of Duchenne / Becker
- pseudochondropathic dysplasia
- Alera syndrome
- Brugada syndrome
- Greig's syndrome
- Gilbert's syndrome
- Joubert's syndrome
- Coffin-Lowry syndrome
- Crigler-Nayar syndrome
- Marfan syndrome
- Nijmegen syndrome
- Pallister syndrome
- Smith-Lemli-Opitz syndrome
- testicular feminization syndrome
- long QT interval syndrome
- Holt-Oram syndrome
- spinal amyotrophy types 1,2,3
- spinal and bulbar amyodystrophy of Kennedy
- Henttigton's chorea
- chronic granulomatous disease
- X-linked agammaglobulinemia
- X-linked lymphoproliferative syndrome (Duncan's disease, Purtillo's syndrome)
- X-linked severe combined immunodeficiency
- Erythrokeratoderma
DNA diagnostics is used to identify a predisposition to hereditary diseases:
- thrombosis;
- alcoholism;
- habitual miscarriage;
- fetoplacental insufficiency;
- non-closure of the neural tube;
- nondisjunction of chromosomes in meiosis;
- sensorineural hearing loss;
- spinal amyotrophy;
To identify a predisposition to insulin-dependent diabetes, typing is carried out for genes of class 1 HLA: A, B, C.
Chorionic villus aspiration
Indications
- Pregnant age> 35 years;
- Complicated obstetric and genetic history (history of the birth of a child with congenital malformations, chromosomal or monogenic disease);
- Changes in the levels of serum blood markers (AFP, hCG);
- Familial carriage of a chromosomal abnormality or gene mutation;
- Echographic data (at 10-14 weeks, the thickness of the collar space> 3 mm, markers of chromosomal diseases, abnormal amount of amniotic fluid).
Methodology
The examination is performed on an outpatient basis in the period from 70 to 91 days of pregnancy, which helps to reduce the number of spontaneous miscarriages and ensures that the amount of material is sufficient for a reliable study. The Center uses a single-needle transabdominal biopsy technique. A 19G aspiration cutting biopsy needle is used, 12 cm long, manufactured, characterized by increased echogenicity. With the help of an ultrasound probe, the puncture trajectory is selected so that the needle passes through the chorionic tissue, parallel to the chorionic sheath. At the beginning of the puncture, it is necessary to ensure that the needle does not damage the bowel loop or bladder. After the needle crosses the myometrium, it is directed parallel to its inner contour. It is necessary to immerse the needle into the chorionic tissue to the maximum depth. After making sure that the needle is in the correct position, remove the mandrel from it and attach a 2-5 ml syringe filled with a transport medium. Constantly performing aspiration, 4-5 movements of the needle back and forth are performed in the thickness of the chorion. The needle is removed while maintaining aspiration. The contents of the syringe are transferred into a transparent shipping container. The quantity and quality of the received material is assessed. If it is not enough, then the procedure can be repeated immediately without additional risk.
Chorionic biopsy
The material is sent for cytogenetic research.
Main results
- The frequency of obtaining the required amount of fetal material: 94 - 99.5%
- Retroplacental hematomas
- Bleeding
- Painful sensations
- Chorioamnionites
- Abortion
Cordocentesis
Indications
- Pregnant age> 35 years
- Complicated obstetric and genetic history (history of the birth of a child with congenital malformations, chromosomal or monogenic disease)
- Changes in the levels of serum blood markers (PAPP, hCG)
- Familial carriage of a chromosomal abnormality or gene mutation
- Echographic data (at 10-14 weeks, the thickness of the collar space is> 3 mm, at 20-24 weeks - the presence of congenital malformations, markers of chromosomal diseases, an abnormal amount of amniotic fluid)
Methodology
The examination is performed on an outpatient basis in the period from 20 to 22 weeks of pregnancy, which helps to reduce the number of spontaneous miscarriages and ensures that the amount of material is sufficient for a reliable study. The Center uses a single-needle technique. A standard spinal puncture needle with a diameter of 22G and a length of 9 cm is used. Under the control of ultrasound scanning by the "free hand" method, a puncture of the umbilical vein is performed. There are several types of access to the umbilical cord
The scheme of puncture of the umbilical vein. Various accesses to the umbilical cord
After the needle is inserted into the umbilical cord, the mandrel is removed from it and, by attaching a syringe, 1 ml of blood is aspirated. A small amount of an anticoagulant (heparin) is pre-filled into the syringe. The blood is poured into tubes with an appropriate medium and sent for cytogenetic research.
Main results
- Frequency of obtaining the required amount of fetal material: 96-99%
- The frequency of detection of chromosomal pathology when using invasive diagnostic methods - 5.1% (according to the Russian multicenter study)
- umbilical cord hematoma,
- fetal bradycardia,
- termination of pregnancy,
- premature birth
Puncture of fetal kidney cysts
Indications
- large solitary kidney cysts, leading to compression of the fetal organs
- multicystosis of one kidney, leading to compression of the fetal organs
- normal fetal karyotype
- combination of fetal kidney cysts with other abnormalities or chromosomal abnormalities
- combination of fetal kidney cysts with obstructive uropathy
Under the control of ultrasound scanning, in compliance with all aseptic rules, a 22 G needle is used to puncture a solitary cyst or sequentially the largest cysts of the fetal kidneys. As much content as possible is aspirated.
The needle is removed. Subsequently, ultrasonic monitoring is performed. With an increase in the size of the cysts, repeated punctures are performed.
Main results
Possible complications are not described in the medical literature.
Puncture of the urinary system in obstructive uropathy, it is performed in fetuses that are not sufficiently mature to survive in the extrauterine conditions
Indications
- persistent lower urinary tract obstruction
- progressive bilateral hydronephrosis
- signs of deterioration of the fetus or pathological changes in its structures
- a combination of obstructive uropathy with other anomalies or chromosomal abnormalities
- combination of obstructive uropathy with renal cysts
Under the control of ultrasound scanning in compliance with all the rules of asepsis, a 22 G needle is used to puncture the calyx-pelvic system or the fetal bladder. The maximum possible amount of urine is aspirated. The needle is removed. Subsequently, ultrasonic monitoring is performed. When the urinary system expands to its previous size, repeated punctures are performed.
Main results- reduction of compression of the fetal organs by enlarged kidneys and bladder.
Possible complications not described in the medical literature.
Determining the sex of the fetus
Indications
- Medical (the presence of monogenic diseases in parents, the inheritance of which is related to gender)
- Social (parents wish)
Methodology
- Chorionic villus sampling at 10-12 weeks + cytogenetic study of fetal karyotype
- Cordocentesis at 20-22 weeks + cytogenetic study of the fetal karyotype
Possible complications
- fetal-maternal bleeding,
- umbilical cord hematoma,
- fetal bradycardia,
- termination of pregnancy,
- premature birth
Establishing the biological paternity of the fetus
Indications
- by court ruling
- at the request of the father with the consent of the female
Contraindications- Acute inflammatory diseases
Methodology
Chorionic villus sampling at 10-12 weeks + blood tests of both parents
Cordocentesis at 20-22 weeks + blood tests of both parents
Main results- determination of the relationship of the fetus and the alleged father with an error probability of no more than%
Possible complications
- fetal-maternal bleeding,
- umbilical cord hematoma,
- fetal bradycardia,
- termination of pregnancy,
- premature birth
Throughout the entire period of bearing a child, expectant mothers are tested and undergo various examinations so that doctors have the most accurate data on the course of pregnancy and can respond in time to any, even the smallest deviations. Chorionic villus sampling is also a diagnostic method, only the analysis is taken invasively (with penetration into the amniotic fluid). That is why women are worried about whether BVH is safe and whether it will harm the embryo.
The essence and purpose of diagnostics
Chorionic villus sampling is a sampling of material directly from the placenta for further research in order to determine the karyotype of the fetus.
From your school biology course, you probably remember what chromosomes are. The chromosome set determines not only the structure of a single cell, but also the entire organism as a whole.
Each cell carries the so-called DNA code, which is also responsible for the presence or absence of hereditary genetic diseases. A karyotype is a qualitative and quantitative indicator of a set of chromosomes.
Analysis of the karyotype of the fetus makes it possible to diagnose severe pathologies of the development of the embryo at the earliest stages of pregnancy, when other invasive procedures are strictly contraindicated.
Invasive procedures are medical procedures that involve penetration through natural barriers. During pregnancy, it is possible to conduct a biopsy of the chorionic villi, amniocentesis, cordocentesis.
Chorion and its villi
Chorionic villi are protrusions of the placenta, resembling small pimples in appearance. Each villi contains a DNA code that is identical to the chromosomal set of fetal cells.
During the procedure, the doctor takes material for research on the karyotype. The complexity of manipulation is justified by the high accuracy of the analysis results, which make it possible to determine the presence or absence of more than 3,800 genetic diseases, including Down's syndrome.
Video "What are chorionic villi?"
Differences from amniocentesis
Amniocentesis is a procedure for taking amniotic fluid for the purpose of examining it for pathologies and diseases. Sometimes, on the contrary, in this way drugs are injected into the amniotic fluid. Manipulation is allowed to be carried out no earlier than 16-20 weeks of pregnancy. In addition, the difference from BVH is as follows:
- a biopsy is performed at 10-13 weeks of pregnancy, and the results are ready 7 days after the test;
- with amniocentesis, the results will have to wait two to three weeks. Such terms are associated with the growth and development of cultures of bacteria used in laboratories for diagnostics.
The main difference between CVS and amniocentesis is that with chorionic biopsy, a fragment of placental tissue is taken for analysis, and with amniocentesis, amniotic fluid
However, the risk of miscarriage increases with biopsy. In addition, CVH will not be able to identify diseases of the neural tube of the fetus, spina bifida. These pathologies can be really detected only during the amniocentesis procedure.
There is one more nuance: with CVH, placental mosaicism is possible. It occurs in only 1% of cases. In other words, some cells of the placenta will have a normal chromosomal set, while others will have a clear pathology.
Duration of the
In order to conduct a full-fledged study, the chorionic villus should be at least 1 cm in diameter. It reaches this size already by the 7th or 8th week of pregnancy. However, at this time, the procedure is quite dangerous for the fetus, because there is a high risk of disrupting the development of the baby's limbs.
11-12 weeks of pregnancy are considered optimal for manipulation. Later it is not recommended, because already at 13 weeks the chorion forms a baby's place.
Indications
The procedure for taking material for analysis is time consuming, associated with a certain risk, therefore it is not carried out "at will". Of course, with the help of BVH already in the early stages, you can find out the sex of the baby, but no doctor will prescribe it for this very purpose.
Below is a list of indications for which a chorionic villus biopsy may be prescribed for a future mother. Diagnostics is carried out if:
- a pregnant woman over 35 years old. The fact is that with age, the risk of fetal pathologies increases;
- the results of ultrasound (ultrasound screening) indicate a suspicion of pathology;
- future parents are blood relatives;
- in the anamnesis of one of the parents there are genetic pathologies, for example, chromosomal rearrangements, hereditary diseases, developmental defects. Medical history - the patient's medical history. The more complete the history, the more honest the patient was, the easier it is for the doctor to determine the possible risks and the method of treatment;
- some of the relatives have monogenic diseases. For example, cystic fibrosis, phenylketonuria, spinal amyotrophy;
- there is a risk of disease by gender, and therefore it is necessary to determine the sex of the fetus in advance. For example, atrophy of the optic nerve and hemophilia A and B (hemophilia is a violation of blood clotting, in severe stages of the disease, the patient can die from a small cut on the finger, without special drugs the blood cannot be stopped) are transmitted only through the male line;
- there is a child who was born with a developmental defect or with a hereditary disease;
- there are factors such as primary infertility in parents, miscarriages, stillbirths, primary amenorrhea, etc.;
- in the early stages of pregnancy, the expectant mother is exposed to an unfavorable external environment. This includes radiation exposure, inhalation of vaporous poisons. For example, if a woman works in hazardous work;
- in the early stages, the expectant mother took embryotoxic drugs or underwent an X-ray examination.
Contraindications
Each medical procedure has its own contraindications. So, the study is not carried out when:
- threatened miscarriage. Albeit with good intentions, a chorionic villus sampling is a dangerous invasion involving the removal of part of the placenta;
- inflammatory processes, diseases in the vagina, on the cervix or on the skin of the abdomen. The main danger is to transfer the inflammatory process to the uterus, which is fraught not only with miscarriage, but also threatens the health and life of the mother;
- if the woman has HIV infection. The contraindication is very conditional and is associated only with the risk of transmitting HIV to the fetus.
The indications for conducting far exceed the weight of the contraindications, and the risks are justified. The main condition is to choose a clinic and a qualified doctor.
The patient should understand that chorionic villus sampling is not prescribed for the sake of parental curiosity or at the whim of a doctor.
Training
Preparation for the procedure does not take much time and does not require much effort. Moreover, the expectant mother will pass all the tests necessary for the procedure when she is registered for pregnancy.
In order to undergo a chorion biopsy, you need to have with you:
- identification;
- referral from a doctor of genetics;
- results of blood tests for infections such as syphilis, HIV, hepatitis B and hepatitis C (all tests should be performed no earlier than 3 months before the procedure);
- a general blood test with a leukocyte formula, done not earlier than a month ago;
- general urine analysis;
- microscopy of vaginal smears;
- research and characterization of the mother's blood by the Rh factor.
In addition, sometimes a woman may be asked to bring all the data recorded from the protocol of the last ultrasound examination, etc.
You should also pay attention to a couple of nuances. The first concerns expectant mothers.
Patients with negative blood Rh factor are required to buy a capsule with anti-Rh immunoglobulin before the procedure. It should be entered no later than 48 hours after the manipulation. In some cases, this is done immediately in the clinic.
HIV-infected women will need to receive more intensive antiretroviral therapy because of 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 penetrate into the uterus through an abdominal puncture. 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 criteria. Both methods involve the use of an ultrasound machine, which allows the doctor to monitor the movement of the needle, the amount of tissue taken for analysis, and possible risks. Without this device, BVH would be impracticable.
BVH - transabdominal method
The procedure is similar to a simple operation. The woman lies down on the operating table, then she is given an injection of a local anesthetic in the place where the puncture will be made. With the help of a needle, they gently penetrate the abdominal wall, the walls of the myometrium and, finally, reach the chorion. The needle must be placed parallel to the shell to avoid damaging it.
The doctor, using a syringe with a nutrient medium, captures the required amount of chorionic villus tissue (at least 5 mg) and removes the syringe.
During a puncture of the abdominal cavity, a woman may experience small cramps that resemble menstrual pain.
CVC - transcervical method
Outwardly, the manipulation is similar to a simple examination by a gynecologist. The patient is placed on a gynecological chair, the walls of the vagina and the cervix are fixed with special forceps, with the help of a catheter they penetrate the chorionic tissue. Then a syringe is attached to the catheter, after which material for analysis is taken in the same way.
When collecting tissue through the cervix, this resembles a normal smear test.
Chorionic biopsy for multiple pregnancies
Chorionic biopsy in multiple pregnancies requires the professionalism of the doctor performing the procedure. If we talk only about the technical side of the issue, then it can be noted that in order to accurately determine the karyotype of each fetus, the chorionic villi must be taken from each fetus. 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 in complete rest. Usually a woman is allowed to go home with an insistent 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.
Minor cramping that gets weaker over time is normal. If the intensity of the spasms and pain sensations increase, you should immediately consult a doctor.
Also, the reason for contacting the antenatal clinic is abundant watery or bloody vaginal discharge. These are signs of spontaneous abortion, in other words, miscarriage.
results
The complete 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 gives a reaction to mutations in villous cells.
In order to conduct a thorough check, it takes two weeks. Such an analysis gives the right to assert that the result is 99% accurate.
It is possible to know the preliminary results in 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. At the same time, in each laboratory, in any case, the analysis will be performed using the traditional method.
To obtain the most accurate result, the material taken from the patient must undergo a certain exposure. Therefore, the traditional method is preferable.
Analysis reliability
The accuracy of the analysis results is 99%. The remaining percentage is given to the possibility of error due to the likely mosaicism. If the doctor suspects a similar pathology in the patient, she will definitely be directed to undergo another invasive procedure - amniocentesis or cordocentesis. But already at a later stage of pregnancy.
In addition, human error or chance should not be completely ruled out. For example, it happens that the doctor during the procedure takes not enough tissue in order to carry out a full analysis.
It is also quite rare, but it happens that the chorionic tissue cannot be cultured. In such cases, the patient is referred for a second chorionic villus sampling.
In some laboratories, errors are possible that are based on human factors. Or such phenomena as contamination of the biopsy specimen with maternal cells (this is when the analysis displays only the state of the placenta in the place where the material was taken from, and not the state of the fetus). That is why it is worth paying attention to the equipment and novelty of the equipment in the clinic in which you are going to undergo the procedure.
If there is any doubt about the reliability of the CVS analysis, the patient is prescribed amniocentesis. Statistics say that in most cases the results of the studies carried out are identical. The percentage of errors is small.
Risks and consequences
Before carrying out the procedure, the expectant mother should weigh all the pros and cons, take into account all the risks. Lack of information breeds 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. A needle puncture of natural barriers will inevitably lead to rupture of capillaries. As a result, a retrochorial hematoma may form. Again, it can lead to miscarriage.
The risk of intrauterine infection is 0.1–0.5%. Recall that this incident threatens the life of not only the child, but also the mother.
Statistics of early complications of biopsy
- 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.
- Parietal hematomas may form, which provoke detachment of the ovum.
- There is a risk of intrauterine infection.
Statistics of late complications of CVH
- Premature birth sometimes occurs.
- The baby may be small.
Is it obligatory to conduct an analysis?
Chorionic villus sampling is not one of the tests that the doctor will insist on. The excitement 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 is the risk of refusal?
Refusing to carry out the procedure, a woman throughout the entire period of gestation will experience permanent stress, which can provoke a miscarriage or freezing of the fetus.
Chorionic villus sampling is necessary not only to decide whether to terminate a pregnancy or apply some kind of intrauterine treatment, but also to prepare for childbirth. If you do not carry out this procedure, 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;
- not knowing what to prepare for, parents can get severe psychological trauma after the birth of a baby with developmental disabilities.
Where can I get tested, cost and reviews
Pricing policy is not something that should be paid attention to when choosing a polyclinic for undergoing the 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 appreciating the professionalism of the clinic's medical staff.
The approximate cost of a chorionic villus sampling varies from 6,000 rubles to 27,000 rubles.
As for the reviews. There are both positive and negative. And mostly subjective factors are to blame for this. It all depends on the qualifications of the doctor performing the manipulation. And also from the pain threshold of a woman. Therefore, it will be more reliable to rely 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 we compare the degree of risk with the possibility of obtaining accurate results on the condition and development of the fetus already in the early stages of pregnancy. So you should not refuse the analysis if it is prescribed for you for medical reasons. Only take full responsibility for the choice of the clinic in which you will take it.
Chorion biopsy is an invasive procedure that involves obtaining chorionic villi for subsequent examination in order to diagnose congenital and hereditary diseases of the fetus.
SYNONYMS
Chorionic villus sampling, chorionic villus aspiration.
CLASSIFICATION
By access technique:
· Transabdominal;
· Transcervical.
According to the technique of execution (transabdominal chorinbiopsy):
· Single-needle;
· Two-needle.
INDICATIONS FOR CHORION'S BIOPSY DURING PREGNANCY
· The age of the pregnant woman is 35 years and older.
· The presence in the family of a child or the identification in previous pregnancies of a fetus with Down syndrome or other chromosomal diseases.
· The presence in the family of a child with multiple congenital malformations.
· Parental karyotype abnormalities.
· Presence of biochemical and / or ultrasound markers of chromosomal diseases or congenital malformations in the fetus.
· Determination of the sex of the fetus in the presence of X linked gene diseases.
RELATIVE CONTRAINDICATIONS
· Acute inflammatory process or exacerbation of a chronic inflammatory process of any localization.
· Presence of clinical and / or ultrasound signs of threatening or incipient abortion.
PREPARATION FOR RESEARCH
Before chorionic biopsy, an ultrasound scan is performed to clarify the gestational age, the presence of fetal heartbeat, the localization of the chorion, the length of the cervical canal, and the state of uterine tone. Perform standard processing of the operating field.
ANALYSIS METHODS
In most cases, it is performed without anesthesia.
OPERATING TECHNIQUE
Chorion biopsy is performed at 10–12 weeks of gestation. Moderate bladder filling is required for optimal imaging.
Chorionic villus sampling can be done by transcervical or transabdominal access. The choice of access is determined by the attending physician, taking into account the localization of the chorion.
A transabdominal biopsy is preferred. It is produced by the free hand method or using a puncture adapter. The use of the puncture adapter is preferable, since it allows you to select the trajectory of the puncture needle movement using the trace on the monitor screen and control the depth of its immersion. There are two techniques for trasabdominal chorionic villus sampling: one-needle and two-needle. The single-needle method consists in sequential puncture of the abdominal wall, uterine wall, and chorionic tissue with a standard 20G needle. Two-needle method: using a guide needle (16-18G) and a smaller internal biopsy needle (20G). With the single-needle technique, the needle is directed into the chorionic tissue, placing it parallel to the chorionic membrane. After the needle crosses the myometrium, it is directed parallel to its inner contour. As with transcervical biopsy, the needle should be immersed in the chorionic tissue while remaining parallel to the chorionic sheath. After making sure with the help of ultrasound in the correct position of the needle, the mandrel is removed from it and a syringe with 5 ml of transport medium is attached.
Removing the needle is also accompanied by an aspiration process. In the absence of conditions for transabdominal access, a transcervical biopsy is performed.
Transcervical biopsy is preferred when the chorion is located at the back of the uterus. The manipulation is carried out while the patient is in the gynecological chair. Sometimes, to change the position of the uterus, its cervix is fixed with bullet forceps. For transcervical access, a polyethylene catheter is used, inside which a flexible mandrel is placed, obturating its lumen and providing it with the necessary strength.
The proximal end of the catheter has an adapter that allows it to be connected to conventional Luer-type syringes. The catheter is sequentially advanced through the cervical canal, the internal pharynx, then directed between the chorionic membrane and the wall of the uterus, into the chorionic tissue. The mandrain is removed from the lumen of the catheter, a 20 ml syringe containing about 5 ml of culture medium is attached to it. Due to the negative pressure created in the syringe, the villi are aspirated, gradually removing the catheter from the chorionic tissue.
In the two-needle technique, a needle of a larger diameter (outer) is used as a trocar, which is inserted into the myometrium, and a thinner and longer (inner) needle is immersed directly into the thickness of the chorion. Then the mandrel is removed from it and the syringe is attached. Further, aspiration is carried out in the same way as in the one-needle technique.
Most genetic studies require at least 5 mg of chorionic tissue. If not enough material is received on the first attempt, the procedure can be repeated without additional risk.
The risk of termination of pregnancy will significantly increase after the third attempt.
The reason for false-positive and false-negative results of a laboratory study of a biopsy specimen can be: contamination of the material with mother cells, as well as the presence of mosaicism limited to the placenta, which occurs in 1% of studies. When placental mosaicism is detected, an additional cordocentesis is recommended to clarify the diagnosis.
PATIENT INFORMATION
Before the procedure, the patient is informed about the indications, the technique of performing, the possible risk of chorion biopsy, and informed consent is obtained for its implementation.
COMPLICATIONS
Bloody discharge from the genital tract
After transcervical chorionic biopsy, they are found in every third patient. In most cases, spotting stops on its own without affecting the outcome of pregnancy. In 4% of cases, after a biopsy, a retrochorial hematoma may form, which usually resolves before the 16th week of pregnancy. With transabdominal access, bleeding from the genital tract after surgery occurs in isolated cases.
Infectious complications
The risk of developing chorioamnionitis does not differ from the population risk and is about 0.3%.
Violation of the integrity of the membranes
A rare complication (in 0.3% of cases), more common with transcervical chorionic biopsy.
Increased serum apetoprotein levels in pregnant women
It is transient in nature, returns to physiological values by the 16-18th week, which makes it possible to carry out biochemical screening of congenital and hereditary diseases of the fetus in pregnant women during these periods.
Development of alloimmune cytopenia in the fetus
After performing chorionic biopsy, prophylactic intramuscular administration of anti-Rh 0 (D) immunoglobulin is recommended for 48-72 hours (depending on the drug used) to Rh-negative non-sensitized pregnant women with a re-positive partner:
· If the test result is received later than 48–72 hours after the procedure;
If, according to the results of chorionic biopsy, a re-positive fetus is determined.
Abortion
In specialized centers, the frequency of spontaneous abortions, premature births after chorionic biopsy is about 2-3%, which corresponds to the general population level.
FEATURES OF POSTOPERATIVE PERIOD MANAGEMENT
Conservation therapy, intraoperative antibiotic prophylaxis and / or therapy (if indicated) are performed.