First prenatal screening. Prenatal screening II trimester. Factors affecting the result

Prenatal screening is a comprehensive examination that the doctor can prescribe to the expectant mother in each trimester of pregnancy.

The first prenatal screening, as well as the next two, can prevent the onset of congenital and hereditary diseases in the fetus.

A screening test is being built on the basis of ultrasound and a biochemical blood test supplementing it, the results obtained allow us to judge the development of the fetus and the health of the maternal organs.

The optimal time for the first prenatal screening is 10-13 weeks of pregnancy. The purpose of this safe comprehensive survey(ultrasound + double test) is to identify possible anomalies and indirect symptoms of the presence of malformations in the fetus at an early stage.

Deciphering the results of the passed screening is carried out using special tables that contain the norms established by specialists, taking into account the gestational age.

The first trimester prenatal test begins with a fetal ultrasound. Based on the data obtained and taking into account the norms given in the table, the doctor can confirm or refute the presence of pathologies.

Deciphering ultrasound KTR and TVP indicators

The first thing the doctor pays attention to during an ultrasound scan of the embryo is its KTR (coccygeal-parietal size). The KTR norms of the first trimester are compared with the values ​​\u200b\u200bgiven in the table below:

KTP indicators in combination with fetal weight are often used to determine the duration of pregnancy.

Minor deviations from the norm indicate that a child can be born either large or small.

If prenatal screening revealed that the CTE values ​​are too high, then with the help of additional studies, the presence of anatomical defects in the fetus is confirmed.

KTR significantly below the norm can be in two cases:

1. not right set time pregnancy (re-ultrasound is done after 7-10 days);
2. the embryo stopped in development, which threatens him with death.

It is possible to exclude the death of the embryo if a heartbeat of normal frequency is detected. Otherwise, curettage of the uterine cavity is performed.

During the ultrasound great attention is given to the study of TVP (thickness collar space), indicators are not deviated from the norm if they have the following values:

The given norms may be slightly lower, but their increase will clearly indicate the development of pathology in the unborn child.

The higher the number, the more likely development in the fetus of Down's syndrome or other chromosomal abnormality, and subsequently there may be irregularities in the work of the heart.

But it is not accepted in medicine to confirm the presence of any chromosomal disease in the fetus only according to the indications of ultrasound of the thickness of the collar space, without additional studies.

Therefore, the doctor may prescribe an additional examination in the form of dopplerometry, as well as blood donation from a vein for biochemical analysis.

BDP and blood biochemistry

Prenatal screening for the first trimester of pregnancy includes determining the BDP of the fetal head, which measures the gap between the inner and outer contours of one and the second parietal bones.

In this case, the line combining the outer contours of both parietal bones should lie above the visual mound of the brain.

Incorrectly performed measurement distorts the results of prenatal screening of the first trimester, which does not allow accurate determination of the gestational age.

At the same time, for the weeks of the first trimester, experts have established a specific standard value for the BDP of the embryo, which can be seen from the following table:

If the prenatal screening test of the first trimester shows that the BDP of the head of the embryo is significantly deviated from acceptable indicators the doctor prescribes additional research.

Increased BDP may be a symptom of the presence of a brain tumor or hernia, the development of hydrocephalus.

In the first case, the pregnancy is interrupted, with hydrocephalus, antibiotic treatment is prescribed.

A greatly underestimated BDP of the head of the embryo also does not bode well, as it is a symptom of underdevelopment of the brain. As a rule, such a pregnancy is terminated.

First trimester screening includes another important indicator- the size of the nasal bone. This marker, like TVP, may be a sign of the development of Down syndrome in the embryo.

Despite the fact that prenatal examination at an early stage (10-11 weeks) does not allow us to estimate the size of the nasal bone, during this period it is still visualized on the screen.

As early as 12-13 weeks prenatal ultrasound should show that nasal bone normal, the size is considered to be at least 3 mm.

Prenatal first biochemical screening involves testing the levels of two hormones, which is why it is also called the "double test".

Biochemical screening helps to identify and determine the level of hCG in the blood of the future mother, as well as to examine the blood plasma for the presence and amount of protein (PAPP).

Both of these substances are in the blood only in women who are carrying a child.

Once the prenatal first biochemical screening has been performed, the transcript finished results carried out in accordance with established standards:

1. the level of hCG of the first trimester should be 0.5 - 2 MoM;
2. the level of PAPP of the first trimester should be from 9 to 13 weeks - 0.17 - 6.01 mU / ml.

A strong deviation from the established standards of the prenatal test may be a symptom of the development of Down or Edwards syndromes, but only a doctor can judge the presence of such pathologies, but taking into account additional examinations.

Prenatal biochemical test of the second trimester

If the prenatal test of the 1st trimester can detect up to 95% of cases of chromosomal abnormalities, then a timely prenatal screening test the second trimester is no less informative in this regard.

But the main purpose of the second prenatal examination is to detect neural tube defects and other fetal malformations, as well as to carry out calculations that subsequently reveal the risk of congenital hereditary or chromosomal diseases, among them:

1. Patau syndrome;
2. hereditary diseases Shershevsky-Turner syndrome and Smith-Opitz syndrome;
3. polyploidy.

As a rule, after the mother has passed the first comprehensive examination, second trimester screening is prescribed either at the request of the future parents, or as prescribed by the doctor in specific cases.

Screening is carried out for the 2nd trimester for a period of 16-20 weeks. Grade biochemical parameters blood of the expectant mother is carried out at 16 - 18 obstetric weeks.

Before donating blood for analysis, a pregnant woman should have with her first trimester ultrasound indicators indicating exact date pregnancy.

Before donating blood for a biochemical analysis, the doctor directing the pregnant woman for examination fills out the 2nd screening questionnaire together with her, where he indicates the results of ultrasound, the term, the parameters of TVP and CRT.

All this data ultrasound examination first trimester, since the second ultrasound at 16-18 weeks is too early to do, it is carried out at 20-21 weeks.

The pregnant woman takes the questionnaire filled out in accordance with all the rules to the laboratory, where they take blood for hCG, AFP and NES.

The main thing is to take tests on an empty stomach, and on the eve of the procedure, do not eat too salty, spicy and fatty foods, which can distort the results.

When the results biochemical screening second trimester are ready, the doctor examines the information received and, comparing with established norms triple test, gives recommendations to the expectant mother or prescribes additional procedures.

AFP, hCG and free estriol

It is by the 16th week of pregnancy that an increased or decreased level of a-fetoprotein in the blood makes it possible to accurately identify a neural tube defect and other defects indicated in the following table.

HCG (chorionic gonadotropin) - is produced first by the membrane of the embryo, then by the placenta.

If the hormone is normal, then the pregnancy is proceeding safely, but if the prenatal biochemical test revealed abnormalities, then there are several reasons for this, which are listed in the table below.

NEZ (unconjugated estriol, free) - the hormone is first produced by the placental membrane, then the fetus itself. With an increase in the duration of pregnancy, an increase in NEZ in the blood of the expectant mother occurs.

A significant decrease or increase in the hormone is a symptom of a pregnancy disorder or pathology of fetal development.

Deviations from the norm can be caused by the following reasons:

EZ - free estriol
Promoted	Downgraded
large fruit	Risk of miscarriage
Multiple pregnancy	Overbearing of the fetus
Risk of occurrence premature birth(at strong rise E3)	intrauterine infection
	Down syndrome
	Neural tube disorder
	Violation of the development of the internal organs of the fetus
	The pregnant woman took drugs prohibited in her position
	Feto-placental insufficiency

Correct interpretation of the results is very important. If the second screening confirmed that the data obtained is not within the normal range, it is imperative to consult a doctor.

Prenatal second screening does not exclude both false negative and false positive results.

Therefore, expectant mothers should not independently interpret the risks, which can, in the end, greatly affect their nervous system.

If the results of the prenatal second screening are very abnormal, then you should not consider given fact sentence, at least until more research is done.

Prenatal screening is a complex special studies, which are carried out by all expectant mothers to determine the risk of developing chromosomal abnormalities in the fetus. These studies are assigned to identify pregnant women who need a more detailed examination.

The presence of genetic abnormalities in the fetus is absolutely accurately shown only by methods invasive diagnostics(that is, involving the invasion of the uterine cavity in order to obtain biological material). However, their use is associated with a certain risk - the threat of abortion, the development of Rhesus conflict with negative Rh factor in a pregnant woman, infection of the fetus and some others. Therefore, these studies are prescribed only to expectant mothers who have a very high risk of fetal abnormalities. It is determined by screening tests. Screening tests are absolutely safe and therefore are carried out for all pregnant women without exception.

Currently, expectant mothers undergo a combined screening, which includes ultrasound examinations and determination of biochemical parameters of blood - special hormones and proteins, the concentration of which changes significantly with genetic disorders fetus.

During pregnancy, it is desirable to undergo two biochemical screenings - in the first and second trimesters (double and triple tests, respectively).

Prenatal screening: double test

This study is carried out strictly in terms from the 11th to the 14th week of pregnancy. Using a double test in the first trimester, the risk of developing Down and Edwards syndromes and some other genetic abnormalities in the fetus is calculated.

In the first screening, two blood parameters are analyzed, which is why this study is also called a double test:

• free b-subunit chorionic gonadotropin human (hCG);
• PAPP-A is a plasma protein A associated with pregnancy. It is produced by the placenta, and its concentration gradually increases during the period of bearing the baby. Greatest growth this indicator is noted at the end of pregnancy. Low level PAPP-A may indicate fetal chromosomal abnormalities.

The risk of genetic abnormalities in the fetus is calculated using special computer programs. simple values the content of hCG and PAPP-A in the blood of a pregnant woman is not enough to decide whether the risk of chromosomal disorders in the fetus is increased or not. They must be converted into special values, the so-called MoM, showing how much this indicator deviates from the average value corresponding to a given gestational age. Thus, if the value of MoM in the future mother is close to one, then it coincides with the average value for all pregnant women for this period. Normally, MoM values ​​should be in the range from 0.5 to 2.

For accurate diagnosis, a blood test is always performed after a fetal ultrasound. This is necessary to clarify the gestational age, detect multiple pregnancy, detection of visible disturbances in the development of the fetus and placenta, etc. All these data are needed for the subsequent processing of the results of biochemical screening.

Deviations from the norm

With Down syndrome free hCG increases to 2 MoM and above, and PAPP-A decreases to 0.48 MoM.

With Edwards syndrome (this is a disease characterized by multiple fetal defects in the presence of an additional 18th chromosome), both indicators are approximately at the level of 0.2 MoM.

With Patau syndrome (when an additional 13th chromosome appears in the fetus and multiple malformations also occur), both MoM indicators are at the level of 0.3–0.4 MoM.

On the analysis form, in addition to the MoM numbers, individual risks are also indicated separately for several diseases. For example, the result can be presented as follows: risk of Edwards syndrome: 1: 1600, risk of Down syndrome: 1: 1200. These figures show, for example, that the probability of having a child with Down syndrome is 1 in 1200 births, that is, out of 1200 of women with such blood test indicators, 1199 healthy children will be born and only one child will be sick.

Chromosomal abnormalities occur in approximately 0.6–1% of newborns. The most common are Down syndrome (frequency of occurrence 1 in 600–700 newborns), Edwards syndrome (frequency of occurrence 1: 6500), Patau syndrome (1: 7800), Shereshevsky-Turner syndrome (1: 3000 newborns).

Prenatal screening: triple test

Biochemical screening of the II trimester is carried out from 16 to 20 weeks of pregnancy (the optimal period is 16–18 weeks). It includes the determination of three indicators: total chorionic gonadotropin (hCG), the hormone estriol and alpha-fetoprotein protein (AFP) and is called a triple test. Some commercial laboratories also test for the hormone inhibin A for greater accuracy.

The triple test allows 80% to detect malformations of the neural tube (that is, the spine, spinal cord and brain), as well as some genetic diseases(Down, Edwards, Klinefelter syndromes).

Alpha fetoprotein (AFP) is a protein produced during pregnancy. Its concentration increases gradually, as the duration of pregnancy increases, reaching a maximum at the 32–34th week, and then gradually decreases.

Deviations from the norm. Elevated levels of AFP, more than 2 MoM, may occur with multiple pregnancies, neural tube defects, umbilical hernia, developmental disorders of the esophagus and duodenum fetus. In Down syndrome and Edwards syndrome, the AFP level usually falls below 0.5 MoM.

Estriol free- the hormone of pregnancy, its concentration increases sharply during the period of gestation. Estriol is produced by the placenta and provides increased blood flow through the vessels of the uterus, active development ducts of the mammary glands and preparing them for breastfeeding. During the normal course of pregnancy, its level is actively growing. With a deterioration in the condition of the fetus, a sharp drop in this indicator can be observed. Normally, the concentration of estriol varies depending on the duration of pregnancy, gradually increasing from 0.45 to 40 nmol / l.

Deviations from the norm. Low levels of estriol are noted in Down syndrome (less than 0.5 MoM), intrauterine infection, the threat of abortion, impaired function of the placenta, manifested in insufficient transport of oxygen to the fetus and nutrients with blood, when taking certain drugs (for example, hormonal drugs and antibiotics).

An increase in the level of estriol by more than 2 MoM is observed with multiple pregnancies, impaired liver function in the expectant mother, and also with the bearing of a large fetus.

Inhibin A- This hormone is produced in the ovaries, placenta and fetal membranes.

Normally, the level of inhibin A also changes with increasing gestational age - from 150 pg / ml in the early stages to 1246 pg / ml at 9-10 weeks, then the concentration of the hormone begins to decrease and at 18 weeks of pregnancy it ranges from 50 to 324 pg / ml.

Deviations from the norm. In Down syndrome, the level of inhibin is increased (more than 2 MoM). The concentration of inhibin A can also be influenced by external factors, for example, the level of inhibin in women who smoke is increased, and with high body weight it is reduced. When calculating the risk of developing fetal malformations, these factors must be taken into account.

It must be remembered that the concentration of b-hCG, PAPP-A and AFP in the blood can change not only with chromosomal abnormalities, but also with other complications of pregnancy: the threat of abortion, intrauterine retention development, fetoplacental insufficiency, late toxicosis (gestosis). Also, the value of biochemical parameters is affected by the intake hormonal drugs and multiple pregnancy.

Prenatal screening: new in diagnostics

At the moment in prenatal diagnosis a new type of research has been introduced - a non-invasive prenatal test. This analysis is based on the detection of fetal DNA in the blood of a pregnant woman, followed by the study and assessment of the likelihood of the presence of underlying genetic diseases. This method is very accurate (its accuracy is 99%) and absolutely safe for the expectant mother and fetus. However, these analyzes are not carried out in all laboratories and they are quite expensive.

If you are at risk...

Many expectant mothers, having received not very nice results biochemical screening, begin to worry strongly. But you shouldn't get upset. It must be understood that the probability of detecting a disease and the development of this disease is not the same thing. Revealing increased risk any deviation from normal flow pregnancy or normal fetal development is by no means a diagnosis. Pregnant women who are at risk are required to conduct special additional studies to confirm or exclude the presence of pathology. Such expectant mothers are offered to undergo invasive diagnostics. For example, amniocentesis - amniotic fluid sampling with a special needle through a puncture of the anterior abdominal wall or through the cervical canal, cordocentesis - taking blood from the umbilical cord of the fetus and other studies.

Important addition

In the past few years, some commercial laboratories have also measured placental growth factor (PLGF) concentrations in their first trimester prenatal screening. This is a protein that is synthesized by the placenta and is involved in the formation of its vessels. This marker shows the likelihood of fetal growth retardation and the development of preeclampsia (a serious complication of the second half of pregnancy, which is manifested by an increase blood pressure, edema, the appearance of protein in the urine and requires emergency early delivery).

In a normal pregnancy, PLGF levels increase in the first and second trimesters and then decrease. In pregnancy complicated by preeclampsia, this indicator is reduced already in the first two trimesters. If an increased risk of this dangerous state and fetal growth retardation, special treatment is prescribed, early start which can significantly reduce the incidence of these diseases.

Mandatory or not?

More recently, all expectant mothers, without exception, had to undergo screening of the II trimester. But by order of the Ministry of Health of Russia No. 572n dated November 21, 2012, its mandatory women's consultations was cancelled. However, many commercial clinics continue to conduct this study.

A set of special examinations, which is recommended for all pregnant women for the timely detection of chromosomal and genetic abnormalities that cannot be treated, is prenatal or prenatal screening. This set of examinations includes safe for the child and mother biochemical analyzes blood and ultrasound examinations certain stages pregnancy (during each trimester). Today, screening diagnostics is recommended for absolutely all pregnant women.

What is prenatal diagnosis used for?

A woman has every right to refuse to undergo this set of examinations if she does not want to. Many do not see the point in identifying defects that cannot be treated, especially on later dates(during the II or III trimester). Prenatal screening for trisomies helps women with negative test results to choose between termination of pregnancy and the birth of a child with a chromosomal pathology.

Having received such information in advance, the patient can mentally prepare for the fact that she will have to raise a special baby. If the screening of the first, second and third trimester shows the absence of pathologies, then a woman can calmly, without worries and worries about the health of the child, endure it.

There are specific indications for prenatal screening:

• age over 35;
• the presence of such diseases in close relatives;
• the birth in this family earlier of children with genetic and chromosomal disorders, birth defects development;
• a history of interrupted pregnancies, where the examination showed the presence of such pathologies in the fetus;
• various adverse effects on one of the parents shortly before conception (for example, radiation exposure) or the intake of teratogenic drugs by one of them.

Screening gives women the opportunity to prevent or prepare for future difficulties, and for some it helps to reassure that everything is in order. This is especially important for those women who are at risk of having a child with chromosomal disorders. All tests and examinations are absolutely safe for the health of mother and baby.

Characteristics of the most common trisomies

If at the moment of division of the mother's or father's germ cell one or more chromosomes are not separated, then gametes of unequal number of chromosomes are formed. They should contain 23 chromosomes, and with some violations, there are 24 chromosomes. Merging gametes should form one full-fledged cell with a normal set of chromosomes in the amount of 46. When an extra 47 chromosome is added to the cell, they speak of trisomy.

Many deviations in the number of chromosomes are incompatible with life, some of them are rare. Life expectancy depends on the number of physiological disorders affecting important organs and systems. The mental retardation of children with trisomies can also be different: from moderate to very serious. The most common trisomies are Down syndrome (on the 21st chromosome), Edwards (on the 18th) and Patau (on the 13th). Children with such pathologies survive, but they need the care and help of loved ones.

Diagnosis of trisomy in the first trimester of pregnancy

The first prenatal screening for trisomies is recommended between 10 and 14 weeks of gestation. Most optimal timing during the first trimester is 11–13 weeks. An ultrasound examination is required main goal which is the measurement of the collar space in the fetus. The collar space is called the place in the neck of the child, where between soft tissues and fluid accumulates in his skin. If this value more than normal, then further examination is prescribed to exclude or confirm anatomical anomalies. In addition, the coccyx-parietal size is measured for more exact definition terms of pregnancy.

A biochemical analysis of venous blood at this stage (the so-called "double test") is carried out in order to determine the level of hCG and PAPP-A - specific placental proteins. It should be carried out no later than 1 week after the first ultrasound screening is done during the first trimester (preferably at 11-13 weeks). The content of PAPP-A in the blood during pregnancy is constantly increasing. This substance provides normal development and growth of the placenta. An insufficient amount of it in the blood from the 8th to the 14th week of pregnancy may indicate the presence of abnormalities.

A decrease in the level of PAPP-A indicates the possible presence of a child with Down syndrome, Cornelia de Lange or Edwards. Elevated levels of hCG can speak not only about possible development Down syndrome. It increases with multiple pregnancy (the value increases several times according to the number of fetuses), an incorrectly set period and diabetes in the mother. These values ​​may also be affected by certain medications and the weight of the pregnant woman.

The result of the ultrasound and the data from the analyzes of the first trimester should be interpreted and calculated by a geneticist or an obstetrician-gynecologist. There are special formulas for this. computer programs. Based on these data and individual characteristics pregnant patient (her ethnicity, age, obstetric history, the presence of genetic abnormalities in relatives), the doctor can put a woman at risk for Edwards or Down syndromes and neural tube defects.

In some cases, a geneticist may recommend that a woman undergo an additional chorionic villus biopsy. This examination gives an absolutely accurate answer to the question: does the child have chromosomal abnormalities, but may lead to pregnancy complications, miscarriage or bleeding. The result of blood tests can be false positive when there is a threat of termination of pregnancy or dysfunction of the placenta. Therefore, screening can detect not only chromosomal abnormalities, but also other pathologies.

Diagnosis of trisomy in the second trimester of pregnancy

If a woman is scheduled for second trimester screening, this is not a cause for concern. These analyzes are recommended to everyone without exception. Prenatal screening for trisomy II trimester includes a triple biochemical examination from weeks 16 to 20 (blood tests for the level of hCG, AFP and free estriol), and from weeks 20 to 24 - an ultrasound study. Triple screening blood for hormones is most indicative from 16 to 18 weeks. The later it is carried out, the more difficult it is to interpret the results.

If the second screening shows an elevated AFP level, the child may have neural tube defects, Meckel's syndrome, liver necrosis, or umbilical hernia. A decrease in AFP levels indicates Edwards syndrome, Down syndrome, fetal death, or an incorrectly determined gestational age.

Estriol is first produced by the placenta and then by the fetal liver. Therefore, if the pregnancy proceeds safely, its level is constantly increasing. A decrease in this substance in the blood of a pregnant woman may indicate the presence of chromosomal abnormalities, intrauterine infection, placental insufficiency, and other pathologies. Too high a titer of this hormone is found in multiple pregnancies or large fetuses.

Based on the results of these examinations, if necessary, the doctor can refer the woman for analysis by invasive diagnostic methods (cordocentesis and amniocentesis). This analysis involves the invasion of the body of a pregnant woman in order to obtain samples for research, it can cause the development of some complications. The risk is approximately 2%.

Diagnosis of trisomy in the III trimester of pregnancy

At 32–34 weeks of gestation, a third ultrasound is performed, which can reveal malformations of the child with a late manifestation. In addition, the state of the placenta is carefully studied, the amount of amniotic fluid and the position of the child in the uterus are assessed. If necessary, conduct cardiotocography and Doppler study. These third trimester examinations allow you to monitor the condition of the fetus in late pregnancy.

With Doppler ultrasound, the degree of blood supply to the fetus is assessed using ultrasound: they check the speed of blood flow in the aorta and cerebral artery baby, as well as in the vessels of the umbilical cord and uterus. Based on the data of this analysis, a conclusion is made about whether the child receives enough oxygen and nutrients, whether he is still comfortable in his mother's stomach. If the result shows insufficient blood supply, then the woman is prescribed drugs that improve blood flow and strengthen blood vessels. Sometimes they resort to emergency delivery.

During the ultrasound examination, the limbs of the fetus, the trunk, the head are measured for the second and third times, the fingers and toes are counted, the structures of the brain are examined, internal organs. This, with a high degree of probability, makes it possible to identify or exclude many pathologies.

The length of the nasal bone, the fronto-occipital and biparietal dimensions, the circumference of the abdomen and head, the length of the bones of the lower leg, shoulder, thigh and forearm, as well as the shape of some parts (nose, jaw, forehead) may be indicators of various anomalies.

What does newborn screening show?

There are a number of tests that are performed on newborns in without fail and at the request of the parents. Mandatory examinations reveal:

• phenylketonuria;
• galactosemia;
• congenital hypothyroidism;
• cystic fibrosis;
• androgenital syndrome.

In order to exclude or identify these 5 severe hereditary diseases, on the 4th day of a child's life, the first screening is carried out - the so-called heel test. A few drops of blood are taken from his heel. The result of the examination is sent to the site where the baby will be observed in the future. If it is negative, then parents are not informed. And if one or more pathologies are confirmed, the doctor informs the parents or guardians of the baby about this and selects a specific treatment that will help avoid the child's disability in the future.

Additionally, it is possible to diagnose another 37 different metabolic disorders linked to heredity: the absence of certain enzymes or their insufficient activity. These include aminoacidopathy and aciduria.

Prenatal or prenatal screening of a pregnant woman, as well as newborn screening, can identify various pathologies and prevent the development of complications. In most cases, these examinations give negative results, which gives the child's parents confidence that their baby is healthy and does not have chromosomal disorders, some of which can be detected only after several years of the child's life, if such an examination is not carried out.

With the development of medicine, more and more attention is paid to timely diagnosis diseases on early stages, this also applies to the examination of the fetus even before its birth. For this purpose, prenatal screening is carried out, the main task of which is to identify risk groups among pregnant women for the birth of a child with hereditary pathology.

Prenatal examination - what is it?

The very word "screening" in translation from in English means "sifting", "selection". This is one of the public health strategies that aims to identify pathology in asymptomatic individuals.

Represents a complex medical research(laboratory, ultrasound), which are carried out to detect a risk group for the occurrence of malformations in a child during pregnancy, which is why it is called "prenatal", which means "prenatal". Also to mark this survey use the term "perinatal screening".

• the woman's age is under 18 and over 38;
• a history of 3 or more pregnancies;
• woman's illnesses diabetes, anemia, arterial hypertension and other diseases, and bad habits future mother;
• complicated pregnancy in history;
• physiology of the pregnant woman.

But even if a woman is at risk, this does not mean that the baby will certainly develop a defect. Screening examination can detect both genetic abnormalities and other pathologies.

Ultrasound is one of the most important tools for prenatal examination. Fetal imaging and reproductive system future mother on the monitor allows you to see all the changes, identify genetic abnormalities on the early dates

What genetic diseases can be detected?

The main violations include:

1. Down Syndrome. It is manifested by trisomy on chromosome 21, that is, in humans, instead of 46 chromosomes, 47 are formed. These children are characterized by: a flat face, hypermobility in the joints, an open mouth with a large flat tongue, severe mental retardation. Often they develop cataracts, a congenital heart disease. Possible congenital leukemia.
2. Patau syndrome. Trisomy 13 occurs in the genetic apparatus. Usually these are children with low weight, delay mental development, disorders of the central nervous system and of cardio-vascular system. Often there are lesions of the pancreas and kidneys. Outwardly manifested by a sloping forehead, a cleft palate and upper lip, deformation of the auricles and nose, and other signs.
3. Edwards Syndrome. It is manifested by violations and trisomy of the 18th chromosome. Severe mental retardation, defects of the skull and auricles, heart defects, skeletal anomalies, and muscle hypotension are often observed.
4. Anencephaly (neural tube defects). This is a 100% lethal pathology, half of the children die before birth, the rest - in the first weeks of life.
5. Shereshevsky-Turner syndrome. Monosomy occurs on the X chromosome. Manifested by a strong lag in sexual development, short stature, deformation chest, which takes on a barrel shape, an abnormal physique, shortening of the neck and defects in the auricles. Heart defects may develop.
6. Triploid maternal origin. In a child, instead of 46 chromosomes, 69 are formed. It is manifested by developmental disorders, heart defects, and clubfoot.
7. Corneli de Lange syndrome. Clinical picture consists of mental retardation, a decrease and shortening of the heart, convulsions and marble skin, polydactyly, visual impairment, congenital malformations of the kidneys, heart and other organs.
8. Smith-Lemli-Opitz syndrome. It is characterized by a variety of symptoms, the most common: autism, mental retardation, heart, kidney and lung defects, behavioral disorders. Other defects are also possible.

A blood test for biochemistry allows you to track changes in the amount of hormones and, accordingly, identify possible genetic abnormalities. How formerly doctor suspect a chromosomal abnormality, the more likely a woman is to give birth healthy baby

What else will the survey show?

Such important research also reveals:

• Intrauterine fetal death. It is the death of a child before birth, which takes effect various reasons- genetic diseases, pathologies of a pregnant woman, infectious lesions, Rh conflict and so on. Represents a great danger to women.
• intrauterine hypoxia. It is characterized by a lack of oxygen, occurs as a result of certain diseases of the mother, malformations of the umbilical cord and placenta, anemia, congenital malformations of the fetus, and other causes are possible.
• Lag in development. It occurs due to various reasons, usually - violations in the genetic apparatus, age and bad habits of the mother, her illness, unfavorable working and housing conditions.
• late toxicosis. This is a complication of pregnancy that occurs due to various reasons and takes place in several stages. Changes occur in the kidneys, cardiovascular, nervous system mother, putting the child at risk.
• placental insufficiency. A fairly common complication that leads to a delay in the development of the baby.
• premature birth. A complication whose name speaks for itself.

Screening types

Prenatal screening is carried out in the following forms:

1. Biochemical. The laboratory studies the marker proteins that are contained in the woman's blood.
2. Ultrasound screening - absolutely all expectant mothers undergo it at least 3 times during pregnancy.
3. Immunological. It is done to every woman when registering with the LCD. The blood type and Rh factor of both parents are determined, as well as the TORCH complex, which is aimed at identifying infectious diseases mothers influencing the development of the child. This is rubella, herpesvirus and cytomegalovirus infection, chickenpox and toxoplasmosis.
4. Molecular. DNA is analyzed in the mother and father of the child in order to identify the risk of developing certain genetic pathologies, for example, phenylketonuria, adrenogenital syndrome and others.
5. Cytogenetic. It is carried out by a geneticist who calculates the probability of a baby being born with the corresponding diseases. It is based on family history data and the presence of a specific diagnosis in the future parent.

The most popular methods are ultrasound and biochemical prenatal screening. Each has its own advantages and timing.

Genetic prenatal screening is a very popular procedure. Consultation with a geneticist allows you to determine the probability of birth healthy child no deviations. Based on the data on the health of both parents, as well as the anamnesis of their families

Passage of screening and reliability of results

Ultrasound diagnostics

Ultrasound examination is carried out 3 times, with a frequency of 1 time per trimester. At the very first appointment, the doctor will determine the gestational age, coccyx-parietal size, look at the features of attachment to the uterus gestational sac to determine the viability of the embryo. Right now, it is especially important to identify developmental disorders, the detection of which raises the question of further tactics of pregnancy management or its termination.

At the next (second) stage, analyze amniotic fluid and their number, can detect defects in the development of the child, maximum attention is given to the study of the placenta, heart, brain. Usually, when the second ultrasound prenatal screening is performed, it is already possible.

On the last planned study an assessment of the condition of the crumbs is carried out, the position and presentation necessary for the tactics of childbirth are determined. The state of the placenta, oxygen saturation (diagnosis of fetal hypoxia) is determined.

Biochemical screening

As for the biochemical examination, the method is based on the determination of serum markers in the blood of the future mother, the concentration of which changes during pregnancy and with changes in the fetus.

For indications for this screening relate consanguineous marriage(incest), maternal age over 35 years, X-ray examination at early stages of gestation, taking embryotoxic medicines, the influence of adverse factors, chromosomal disorders of parents, a history of unsuccessful pregnancies, etc.

Prenatal screening is an absolutely safe diagnostic method for both the child and the mother. The risk of error is reduced to a minimum, but still a small percentage takes place.

"Double" and "triple" tests

At a period of 10 - 14 weeks, women undergo a "double test" - free β - subunit of human chorionic gonadotropin (β - hCG) and pregnant protein PAPP-A are determined in the blood plasma, for which blood is taken from a vein on an empty stomach in the morning, half an hour before procedures should avoid emotional and physical overstrain. The concentration of PAPP-A is evaluated together with the amount of hCG in the blood. To interpret the data, the designation of the level of serum markers is used. It is calculated as the ratio of the concentration of protein in the blood of a particular woman to the value of the median content of this protein at normal pregnancy this period in a large sample of women. In each state or even a separate region, its own indicator is calculated. The amount of proteins from 0.5 to 2.0 MoM is considered normal.

As for the "triple" test, it is carried out in the second trimester, alpha-fetoprotein (AFP), free estriol, and hCG are measured. To evaluate the results, the definition of the multiplicity of the median MoM is similarly applied. With malformations of the child, a mixed characteristic deviation of the indicators occurs. They are also often referred to as MoM profiles for a specific pathology. If any violation is detected, you should undergo a second ultrasound, which can detect pathologies and clarify the gestational age.

During pregnancy, most expectant mothers undergo a huge number of tests, undergo various manipulations and diagnostic procedures. An important component of these examinations are prenatal screening tests: ultrasound diagnostics in combination with biochemical screening. They are carried out in order to detect the risks of dangerous chromosomal abnormalities in the fetus.

This set of studies can be carried out twice. First time - 10-13 weeks prenatal development fetus, and this is called prenatal screening of the 1st trimester of pregnancy. The second time - to check the results, the tests are taken at the 16-18th week, this is a screening of the 2nd trimester. The first screening is also called a double test, and the second screening is also called a triple test. This is due to the number of tests that a woman must pass. There is also a screening for the 3rd period of pregnancy.

With the help of biochemical screening in combination with ultrasound, it is possible to determine the risks of the unborn child developing such pathologies as trisomy, developmental defects of various organ systems, and so on. For the study, venous blood of the mother is taken, which is further laboratory conditions studied for the presence of markers (hormones) associated with pregnancy. It takes 1.5 to 2 weeks.

If a specialist doctor suspects high risks of having a sick child, the woman is sent for a consultation and additional examinations to genetics.

Biochemical prenatal screening has a number of positive and negative aspects. Benefits this method are its non-invasiveness, in contrast to amniocentesis, cordocentesis, the absence of the likelihood of spontaneous abortion during the procedure, quite informative indicators of the risk of having a sick child. However, it is worth remembering the negative aspects of this method.

The main disadvantages include the possibility of false positive and false negative result. In the first case, in the presence of an absolutely healthy child, the test shows a high risk of pathologies, in the second - on the contrary. But be that as it may, the gynecologist who leads the woman's pregnancy is obliged to send future mother for further investigation before making any decisions.

What tests are included in the list of prenatal biochemical screening?

The complex of analyzes of biochemical prenatal screening of the 1st trimester of pregnancy includes determining the level of:

• Free β-subunit of human chorionic gonadotropin;
• Pregnancy associated protein A (PAPP-A).

In addition, the examination will be inaccurate if an ultrasound is not performed. This diagnostic method must be completed before laboratory research to determine the exact age of the fetus, determine the coccyx-parietal size, as well as the thickness of the collar space.

If for any reason it is necessary to conduct a second test, then this occurs at 16-18 weeks of pregnancy, in the 2nd trimester. During this period, study:

• β-subunit of human chorionic gonadotropin (hCG);
• Alpha-fetoprotein (AFP);
• Free estriol (unconjugated estriol).

These markers are determined after a woman will pass ultrasound diagnostics.

Deciphering the data of prenatal screening of the 1st trimester

During an ultrasound examination, the coccygeal-parietal size should be 45.85 mm or more. The thickness of the collar space is less than 3 mm. The age of the fetus for the information content of the test is from 10 to 13 weeks.

HCG at 10-13 weeks of pregnancy is normally 20 thousand - 90 thousand mU / ml. If the indicators are above the norm, then you can suspect:

• Down syndrome in the fetus;
• Pronounced anomalies in the development of the fetus;
• Multiple pregnancy;
• Diabetes mellitus in pregnancy.
• Reception of certain groups of drugs.

If the hCG levels are below 20 thousand mU / ml, this may indicate:

• About a frozen pregnancy;
• About the lag in the development of the fetus;
• ABOUT high risk spontaneous abortion;
• About the presence of severe chromosomal defects in the fetus.

In a blood test for pregnancy associated protein A (PAPP-A), the expected rate ranges from 0.46–8.54 mU / ml. Each week of pregnancy has its own regulatory framework for this marker. If its level is less than the lower limit of normal, we can assume:

• Non-developing pregnancy;
• The threat of spontaneous abortion;
• Deviations in the fetus at the chromosomal level (Down syndrome, Cornelia de Lange, Edwards and others).

The elevated rates of this study have no diagnostic value. They can only indicate a multiple pregnancy.

Interpretation of prenatal screening data 2nd trimester

As with the first study, you first need to undergo an ultrasound. This time, doctors are interested in biparietal size. After it is installed and all indicators of the fetus are studied using ultrasound, the woman undergoes a triple test.

When decoding analyzes for alpha-fetoprotein (AFP) from 16 to 18 weeks of pregnancy, the following norms were established: 15–95 U / ml. If the indicators are below the norm, then the risks are likely:

• Deviations in the fetus at the chromosomal level (Down syndrome, Edwards);
• Death of the fetus.

At elevated level AFP risks:

• Pathologies of the development of internal organs;
• Pathologies of the development of the nervous system.

Second laboratory analysis in triple test is the definition of unconjugated estriol, the norms of which range from 6.6–25 nmol / l. When reduced level there are risks:

• Fetoplacental insufficiency;
• untimely delivery;
• Chromosomal pathologies;
• Infectious processes in the fetus.

An elevated level of this marker is not used to diagnose pathologies. It can only show the likelihood of multiple pregnancy, large sizes fetus and the presence of certain diseases in the expectant mother.

As in the first screening, the second also determines the norm of hCG, since this hormone accompanies the entire period of pregnancy. Gradually, it increases, and then stabilizes and maintains its concentration until the end of pregnancy. At 16–18 weeks of gestation, the norm is 8000–57000 mU / ml.