Prenatal diagnosis is a complex of pregnancy development surveys . The main goal is to identify a variety of pathologies in the infant at the stages of fetal development.
The most common methods of prenatal diagnosis: ultrasound, the content of various markers in the blood of a pregnant woman, a chorionic biopsy, taking umbilical cord blood through the skin, amniocentesis.
What is prenatal diagnosis for?
Using various methods of prenatal diagnosis, it is realistically possible to detect such disorders as Edwards syndrome, Down syndrome, disorders in the formation of the heart and other deviations in the development of the fetus. It is the results of prenatal diagnosis that can decide the future fate of the child. After receiving the diagnostic data, together with the doctor, the mother decides whether the baby will be born or the pregnancy will be terminated. Favorable prognosis may allow the rehabilitation of the fetus. The determination of paternity by genetic examination, which is carried out in the early stages of pregnancy, as well as the determination of the sex of the fetus, also refers to prenatal diagnosis. All these services in the capital are provided by the Center for Prenatal Diagnostics on Prospekt Mira, headed by Professor M.V. Medvedev. Here you can undergo a comprehensive prenatal examination, including ultrasound. The Center uses modern 3D, 4D technologies.
Prenatal diagnostic methods
Modern prenatal diagnosis uses a variety of methods and technologies. The degree, as well as the level of opportunities they have is diverse. In general, prenatal diagnosis is divided into two large groups: invasive prenatal diagnosis and non-invasive.
Non-invasive, or as they are also called minimally invasive, methods do not include surgical interventions and trauma to the fetus and mother. Such procedures are recommended for all pregnant women, they are not at all dangerous. Scheduled examinations of an ultrasound scan must be taken. Invasive methods involve invasion (intervention) in the pregnant woman’s body, in the uterine cavity. The methods are not completely safe, so the doctor prescribes them in extreme cases, when the question is about maintaining the health of the unborn child.
Non-invasive prenatal diagnosis
Non-invasive methods include ultrasound or prenatal screening, which allows you to observe in dynamics the development of the fetus. Non-invasive is also considered prenatal diagnosis of the fetus by maternal blood serum factors.
Ultrasound is the most common procedure, it has no harmful effects on a woman and the fetus itself. Do all expectant mothers have to go through this study? The issue is debatable, maybe it is not required in each case. An ultrasound is prescribed by a doctor for many reasons. In the first trimester, you can determine the number of pregnancies, whether the fetus is alive, what is the exact period. In the fourth month, ultrasound can already show gross congenital malformations of the fetus, the location of the placenta, the amount of amniotic fluid. After 20 weeks, it is possible to determine the sex of the unborn child. Ultrasound allows you to identify various abnormalities if the analysis showed a high alpha-fetoprotein in the pregnant woman, as well as if any malformations are observed in the family history. It is worth noting that not a single ultrasound result can guarantee a 100% birth of a healthy fetus.
How is an ultrasound performed
Prenatal prenatal diagnosis in the form of ultrasound is recommended for all pregnant women in the following periods:
- 11-13 week of pregnancy;
- 25-35 week of pregnancy.
Diagnosis of the state of the mother’s body, as well as the development of the fetus is provided. The doctor sets the transducer or transducer on the surface of the pregnant abdomen, there is an invasion of sound waves. These waves are captured by the sensor, and it transfers them to the monitor screen. In the early stages of pregnancy, the transvaginal method is sometimes used. In this case, the sensor is inserted into the vagina. What deviations can be revealed by ultrasound screening?
• Congenital malformations of the liver, kidneys, heart, intestines and others.
• Up to 12 weeks signs of Down syndrome.
The development of pregnancy itself:
• Ectopic or uterine.
• The amount in the uterus of the fetus.
• Gestational age.
• Head or pelvic presentation of the fetus.
• Development lag in terms of time.
• The nature of the heartbeat.
• Gender of the child.
• Location and condition of the placenta.
• Blood flow in the vessels.
• Uterus tone.
So, an ultrasound examination makes it possible to detect any abnormalities. For example, uterine hypertonicity can lead to the risk of miscarriage. Having discovered this anomaly, you can take timely measures to preserve the pregnancy.
Blood screening
The blood serum taken from a woman is examined for the content of various substances in it:
• AFP (alpha-fetoprotein).
• NE (unconjugated estriol).
• CG (chorionic gonadotropin).
This method of prenatal screening has a fairly high degree of accuracy. But there are times when the test shows either a false positive or a false negative result. Then the doctor prescribes additional methods of prenatal screening, such as ultrasound or some method of invasive diagnosis.
The Center for Prenatal Diagnostics on Mira Avenue in Moscow conducts biochemical screening, ultrasound examination in just 1.5 hours, and also provides prenatal consultation. In addition to the first trimester screening, it is possible to undergo a biochemical screening of the second trimester along with counseling and ultrasound.
Alpha-fetoprotein Content
Prenatal diagnosis of hereditary diseases uses a method for determining the level of alpha-fetoprotein in the blood. This screening test allows you to identify the likelihood of a baby with a pathology such as anencephaly, cleft spine and others. Also, a high alpha-fetoprotein may indicate the development of several fetuses, incorrect dates, the possibility of a miscarriage, and even a frozen pregnancy. The analysis gives the most accurate results if done at the 16-18th week of pregnancy. Results before the 14th or after the 21st week are often erroneous. Repeated blood donations are sometimes prescribed. With a high rate, the doctor prescribes an ultrasound scan, this allows you to more reliably obtain confirmation of the fetal disease. If ultrasound does not determine the cause of the high alpha-fetoprotein content, then amniocentesis is prescribed. This study more accurately determines the change in alpha-fetoprotein. If the patient’s blood contains an elevated level of alpha-fetoprotein, complications may arise during pregnancy, for example, developmental delay, fetal death, or placental abruption. Low alpha-fetoprotein combined with high CG and low estriol indicate a possibility of developing Down syndrome. The doctor takes into account all indicators: woman's age, hormone content. If required, additional prenatal research methods are prescribed.
HCG
Human chorionic gonadotropin or (hCG) during early pregnancy allows you to evaluate the most important indicators. A plus of this analysis is early determination, when even ultrasound is not informative. After fertilization, the hCG begins to be produced on the 6-8th day.
HCG as a glycoprotein consists of alpha and beta subunits. Alpha is identical with the pituitary hormones (FSH, TSH, LH); and beta is unique. That is why, to obtain the exact result, the beta subunit test (beta-hCG) is used. In express diagnostics, test strips are used, where a less specific hCG test (in urine) is used. In the blood, beta-hCG accurately diagnoses pregnancy already at 2 weeks from fertilization. The concentration for the diagnosis of hCG in the urine matures 1-2 days later than in the blood. In urine, the level of hCG is 2 times less.
Factors Affecting HCG
When determining hCG during pregnancy in the early stages, several factors affecting the result of the analysis should be taken into account.
Increased hCG during pregnancy:
• Inconsistency between the estimated and real terms.
• Multiple pregnancy (increase in the result is proportional to the number of fetuses).
• Early toxicosis.
• Gestosis.
• Serious malformations.
• Reception of progestogens.
• Diabetes.
Decrease in the level of hCG - mismatch of the term, extremely slowed-down increase in the concentration of hCG by more than 50% of the norm:
• Inconsistency between the expected and real terms (more often due to an irregular cycle).
• The threat of miscarriage (the level is reduced by more than 50%).
• Frozen pregnancy.
• Remixing.
• Ectopic pregnancy.
• Chronic placental insufficiency.
• Death of the fetus in the 2-3 trimester.
Invasive methods
If the doctor decides that invasive prenatal diagnosis should be used to identify hereditary diseases, developmental disorders, one of the following procedures can be used:
• Cordocentesis.
• Chorionic biopsy (study of the composition of the cells from which the placenta is formed).
• Amniocentesis (amniotic fluid test).
• Placentocentesis (negative consequences are detected after infections).
The advantage of invasive methods is speed and one hundred percent guarantee of the result. Used in the early stages of pregnancy. So, if there is any suspicion of deviations in the development of the fetus, prenatal diagnosis of hereditary diseases allows us to draw accurate conclusions. Parents and the doctor can make a decision in time: to leave the fetus or to terminate the pregnancy. If the parents, despite the pathology, nevertheless decide to leave the child, the doctors have time to properly manage and correct the pregnancy and even treat the fetus in the womb. If the decision to terminate the pregnancy is made, then in the early stages when deviations are detected, this procedure is physically and mentally much easier.
Chorionic Biopsy
A chorionic biopsy involves the analysis of a microscopic particle of a villous chorionic cell - the future placenta. This particle is identical to the fetal genes, which allows us to characterize the chromosome composition and determine the genetic health of the baby. The analysis is carried out if there is a suspicion of diseases associated with chromosomal errors during conception (Edwards syndrome, Down syndrome, Patau, etc.) or if there is a risk of incurable diseases of cystic fibrosis, sickle cell anemia, and Huntigton's chorea. The result of a chorionic biopsy reveals 3800 diseases of the unborn child. But such a defect as a defect in the development of the neural tube cannot be detected by this method. This pathology is detected only during amniocentesis or cordocentesis procedures.
At the time of the analysis, the chorion thickness should be at least 1 cm, this corresponds to 7-8 weeks of pregnancy. Recently, the procedure is carried out on the 10-12th week, it is safer for the fetus. But no later than the 13th week.
Procedure
The method of puncture (transcervical or transabdominal) is chosen by surgeons. It depends on where the chorion is localized relative to the walls of the uterus. In any case, a biopsy is performed with an ultrasound scan.
The woman is lying on her back. The selected puncture site is necessarily anesthetized with local exposure. A puncture of the abdominal wall, the myometrial wall is made so that the needle enters parallel to the chorionic membrane. On ultrasound, the movement of the needle is controlled. A syringe is used to take tissues of the chorionic villi, the needle is removed. With the transcervical method, the woman is placed on the armchair as during a routine examination. Obviously expressed pain is not felt. The cervix and the walls of the vagina are fixed with special forceps. Access is provided by a catheter, when it reaches the chorionic tissue, a syringe is attached and material is taken for analysis.
Amniocentesis
Methods of prenatal diagnosis include the most common - a method for determining pathologies of fetal development - amniocentesis. It is recommended to conduct it at 15-17 weeks. During the procedure, the fetus is monitored by ultrasound. The doctor through the abdominal wall inserts the needle into the amniotic fluid, sucks out a certain amount for analysis and the needle is removed. Preparing the results of 1-3 weeks. Amniocentesis is not dangerous for the development of pregnancy. In 1-2% of women, fluid leakage may occur, it stops without treatment. Spontaneous abortion can occur only in 0.5% of cases. The needle does not damage the fetus; the procedure can be performed even with multiple pregnancy.
Genetic methods
The DOT test is the latest safe genetic method in the study of the fetus, allows you to identify the syndrome of Patau, Edwards, Down, Shereshevsky-Turner, Klinefelter. The test is based on data that is obtained from the mother’s blood. The principle is that with the natural death of a certain number of placenta cells, 5% of the fetal DNA enters the mother’s blood. This makes it possible to diagnose the main trisomy (DOT test).
How is the procedure performed? Blood is taken from a vein of a pregnant woman, fetal DNA is secreted. The result is issued within ten days. The test is carried out at any stage of pregnancy, starting from 10 weeks. The reliability of the information is 99.7%.