Nutrition and diet 

Echographic signs of chromosomal abnormalities of the fetus. Prenatal diagnosis of chromosomal abnormalities

A chromosomal abnormality is any change in the number or structure of chromosomes. The most famous of these is trisomy on the 21st pair of chromosomes (Down syndrome or Mongolism). In addition, there are many other anomalies. Some of them are incompatible with life and, as a rule, cause miscarriages, others lead to impaired psychomotor development of varying severity, and some changes do not have any adverse manifestations and do not affect a person's life.

The only way to know if your baby has a similar abnormality is to perform tests such as amniocentesis or trophoblast biopsy, which will help determine the karyotype of the fetus. A karyotype is a genetic map of a child. But such studies are carried out only in cases where the risk of a child having a chromosomal abnormality is significantly increased. Therefore, it is very important to accurately assess the likelihood of a chromosomal abnormality.

There are many ways to calculate this risk. They are all well studied from a scientific point of view, but the best method is one that requires a minimum number of analyzes (and, therefore, allows you to reduce the frequency of unjustified miscarriages), and at the same time allows you to determine the risk of possible chromosomal abnormalities as accurately as possible.

Taking into account these requirements, scientists recommend using a method of determining the degree of risk, which takes into account the following three indicators:

The degree of risk associated with the age of the expectant mother: it is known that the risk of a chromosomal abnormality increases with the age of a woman. For example, the probability of a chromosomal abnormality of the mother's fetus at the age of 20 is 1/1500, and by the age of 39 it rises to 1/128;

The degree of risk associated with the thickness of the occipital fold of the fetus. This indicator is determined by a gynecologist during an ultrasound scan in the period from 11 to 13 weeks for amenorrhea;

The degree of risk, determined by the level of certain substances in the mother's blood during the first trimester of pregnancy (beta-hCG and PAPP-A protein).

This does not mean that your child has trisomy on the 21st pair of chromosomes, but starting from this (1/250) degree of risk, the gynecologist suggests an amniocentesis.

It should be noted that amniocentesis is performed only by 5% of expectant mothers (of all age groups), and in 97% of cases in these 5% of women, the study does not reveal any abnormalities in the karyotype of the fetus. Which suggests that the risk of having a chromosomal abnormality is very small.

The final decision to perform amniocentesis or trophoblast biopsy is made only by a pregnant woman, who has every right to either agree to this study or refuse it. The doctor is just helping the woman to make this difficult decision.

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Pregnancy is a long-awaited state of a woman. However, this is also a period of experience. After all, the normal course of pregnancy is far from a guarantee that the baby will be born without pathologies. At an early stage, diagnostic measures are required to help exclude chromosomal pathologies.

Fetal chromosomal abnormalities are the appearance of an additional (extra) chromosome or a violation in the structure of one of the chromosomes. This happens even during intrauterine development.

So, everyone knows about Down syndrome. This is a disease that develops in utero. It is associated with the appearance of an extra chromosome directly in 21 pairs. Thanks to the diagnosis, as well as the external manifestations of the course of pregnancy, it is possible to identify such a pathology even at the early stages of fetal development.

Causes of chromosomal abnormalities

Chromosomal defects can develop for a variety of reasons. Often these are health problems in the mother:

  • infections;
  • problems with the endocrine system;
  • diseases of any internal organs;
  • toxicosis during pregnancy;
  • previous abortions;
  • risk of miscarriage.

An important role is played by ecology, which constantly acts on the woman's body, as well as the features of the environment:


The hereditary factor is also important. Gene mutations, chromosome aberrations are common causes of the development of anomalies.

Already when planning a pregnancy, you need to think about a balanced diet:

  1. All the main ingredients must be present in sufficient quantities in the menu (vitamins, fats, minerals, carbohydrates and proteins).
  2. It is necessary to take care of the presence in the menu of products with micronutrients (polyunsaturated fatty acids, trace elements important for the body). So, a deficiency of an element such as iodine in the body can lead to impaired development of the brain of the unborn child.

Risk factors

There are many risk factors for developing chromosomal abnormalities. On the mother's side, these are problems such as:

There are risks from the fetus:

  • Delayed development.
  • Multiple pregnancy.
  • Presentation anomalies.

Medicines, pregnancy and chromosomal abnormalities

The fetus is affected by many medications that a woman takes during pregnancy:

  • aminoglycosides have a toxic effect on ear and kidney development;
  • aloe helps to increase intestinal peristalsis;
  • antihistamines can cause tremors and markedly reduce blood pressure;
  • androgens are the cause of fetal malformations;
  • anticoagulants can cause problems with bone formation, as well as encephalopathy;
  • atropine is the cause of cerebral dysfunction;
  • belladonna causes tachycardia in the fetus;
  • drugs for lowering pressure significantly reduce blood flow to the placenta;
  • diazepam can harm the appearance of the unborn child;
  • corticosteroids inhibit the functional purpose of the adrenal glands, lead to encephalopathy;
  • caffeine damages the fetal liver;
  • lithium develops heart defects;
  • opiates affect brain activity;
  • anticonvulsants noticeably delay the intrauterine development of the baby;
  • tetracyclines lead to skeletal abnormalities.

Signs

The process of development of anomalies in the intrauterine state has not been sufficiently studied today. That is why the signs of anomalies are considered conditional. Among them:

All these signs can be the norm for the development of the fetus, subject to a similar feature of the organism of the child or mother. Blood tests, invasive techniques and ultrasound will help to make sure that there are chromosomal abnormalities as accurately as possible.

Diagnostics

The main task of diagnostic measures that are prescribed during pregnancy is to identify fetal malformations. Today there are a huge number of methods that allow you to accurately diagnose or exclude the presence of anomalies.

Non-invasive methods:

  • Ultrasound is prescribed for the entire pregnancy 3 times (up to 12 weeks, at 20-22 weeks and 30-32 weeks).
  • Determination of biochemical markers in blood serum. HCG, protein A - deviations from the norm may indicate an ectopic pregnancy or the development of chromosomal abnormalities. Alpha-fetoprotein - a low level indicates the presence of a risk of developing Down syndrome, and an increased level will tell about a possible defect of the central nervous system. Estriol - should normally increase gradually with increasing gestational age.

Invasive techniques:

After the birth of a child, any methods from the arsenal of modern medicine can be used to determine anomalies:

  • radiation methods (CT, CTG, X-ray, ultrasound);
  • endoscopic;
  • research of biological materials;
  • functional tests.

Possible pathologies

The development of many anomalies is observed during specific periods of pregnancy:

  • 3 weeks - ectopia of the heart, absence of limbs, as well as fusion of the feet;
  • 4 weeks - no feet, hemivertebra;
  • 5 weeks - splitting of the bones of the face, as well as such terrible problems as the absence of hands, feet;
  • 6 weeks - complete absence of the lower jaw, as well as heart disease, lens cataract;
  • 7 weeks - absolute absence of fingers, development of a round head, incorrigible cleft palate from above, as well as epicanthus;
  • 8 weeks - no nasal bone, shortening of the fingers.

The consequences of the development of chromosomal problems are very diverse. It can be not only external deformities, but also lesions, disruption of the central nervous system. The pathologies that have arisen depend on what kind of chromosome abnormality occurred:

  1. If the quantitative characteristics of chromosomes are violated, Down syndrome (in 21 pairs - one extra chromosome), Patau syndrome (a severe pathology with numerous defects), Edwards syndrome (often appears in children of elderly mothers).
  2. Violation of the number of sex chromosomes. Then the development of Shereshevsky-Turner syndrome (development of the genital glands according to the wrong type) is likely, polysomies are characterized by various problems, Klinefelter syndrome (disorders in boys on the X chromosome).
  3. Polyploidy usually ends in death while still in the womb.

Gene mutations have not yet been fully studied by scientists. The reasons for their development are still being investigated by specialists. But already in 5% of all pregnant women in the world, genetic abnormalities of the fetus are detected.

The difficult ethical question of whether it is worthwhile to conduct an examination to identify the genetic pathologies of the unborn baby, each pregnant woman decides for herself. In any case, it is important to have all the information about modern diagnostic capabilities.

About what invasive and non-invasive methods of prenatal diagnostics exist today, how informative and safe they are, and in what cases they are used, said Yulia SHATOKHA, Candidate of Medical Sciences, Head of the Department of Prenatal Ultrasound Diagnostics of the Network of Medical Centers "Ultrasound Studio".

Why do you need prenatal diagnostics?

Various methods help predict possible genetic pathologies during pregnancy. First of all, this is an ultrasound examination (screening), with the help of which the doctor can notice abnormalities in the development of the fetus.

The second stage of prenatal screening during pregnancy is biochemical screening (blood test). These tests, also known as "double" and "triple" tests, are used by every pregnant woman today. It allows you to predict the risk of the existence of fetal chromosomal abnormalities with some degree of accuracy.

” It is impossible to make an accurate diagnosis based on such an analysis; this requires chromosomal studies - more complex and expensive.

Chromosomal studies are not required for all pregnant women, however, there are certain indications:

    future parents are close relatives;

    expectant mother over 35 years old;

    the presence in the family of children with chromosomal pathology;

    miscarriages or missed pregnancies in the past;

    diseases potentially dangerous to the fetus, transferred during pregnancy;

    shortly before conception, one of the parents was exposed to ionizing radiation (X-rays, radiation therapy);

    risks identified as a result of ultrasound.

Expert opinion

The statistical probability of having a child with a chromosomal disorder is from 0.4 to 0.7%. But it must be borne in mind that this is a risk in the population as a whole, for individual pregnant women it can be extremely high: the base risk depends on age, nationality and various social parameters. For example, the risk of chromosomal abnormalities in a healthy pregnant woman increases with age. In addition, there is, but there is an individual risk, which is determined based on the data of biochemical and ultrasound studies.

Double and triple tests

Biochemical screenings also known as , and in common parlance referred to at all Down syndrome analysis or "Analysis for deformities", spend in strictly defined periods of pregnancy.

Double test

A double test is done at 10-13 weeks of gestation. In the course of this blood test, they look at the value of such indicators as:

    free hCG (chorionic gonadotropin),

    PAPPA (Plasma Protein A, Inhibitor A).

The analysis should be done only after an ultrasound scan, the data of which is also used in calculating risks.

The specialist will need the following data from the ultrasound report: the date of the ultrasound, the coccygeal-parietal size (CTE), the biparietal size (BPD), the thickness of the collar space (TVP).

Triple test

The second - "triple" (or "quadruple") test is recommended for pregnant women to take place at 16-18 weeks.

During this test, the number of the following indicators is examined:

    alpha-fetoprotein (AFP);

    free estriol;

    inhibin A (in the case of a quadruple test)

Based on the analysis of the data of the first and second biochemical screening and ultrasound, doctors calculate the likelihood of such chromosomal abnormalities as:

    Down syndrome;

    Edwards syndrome;

    neural tube defects;

    Patau syndrome;

    Turner syndrome;

    sdrom of Cornelia de Lange;

    Smith Lemli Opitz syndrome;

    triploidy.

Expert opinion

A double or triple test is a biochemical test that determines the concentration in the mother's blood of certain substances that characterize the condition of the fetus.

How are the risks of chromosomal abnormalities calculated?

In addition to possible chromosomal abnormalities, many factors affect the results of biochemical screening, in particular age and weight. To determine statistically significant results, a database was created in which women were divided into groups according to age and body weight and the average indicators of the "double" and "triple" test were calculated.

The average result for each hormone (MoM) became the basis for determining the normal range. So, if the result obtained when dividing by MoM is 0.5-2.5 units, then the hormone level is considered normal. If less than 0.5 MoM - low, above 2.5 - high.

What is the highest risk of chromosomal abnormalities?

In the final report, the risk for each pathology is indicated as a fraction.

    A risk of 1: 380 and higher is considered high.

    Average - 1: 1000 and below - this is a normal figure.

    The risk is considered very low 1: 10000 and below.

This figure means that out of 10 thousand pregnant women with such a level, for example, hCG, only one had a child with Down syndrome.

Expert opinion

The risk of 1: 100 and higher is an indication for diagnosing the chromosomal pathology of the fetus, but each woman determines the degree of criticality of these results for herself. To some, a probability of 1: 1000 may seem critical.

Accuracy of biochemical screening of pregnant women

Many pregnant women are wary and skeptical about biochemical screening. And this is not surprising - this test does not provide any accurate information, on its basis one can only assume the likelihood of the existence of chromosomal abnormalities.

In addition, the information content of biochemical screening may decrease if:

    pregnancy occurred as a result of IVF;

    the expectant mother has diabetes mellitus;

    multiple pregnancy;

    the mother-to-be is overweight or underweight

Expert opinion

As an isolated study, double and triple tests have little prognostic value, when ultrasound data are taken into account, the reliability increases to 60-70%, and only when genetic analyzes are performed, the result will be 99% accurate. We are talking only about chromosomal abnormalities. If we are talking about a congenital pathology that is not associated with chromosome defects (for example, "cleft lip" or congenital heart and brain defects), then professional ultrasound diagnostics will give a reliable result.

Genetic tests for suspected chromosomal abnormalities

Based on the conclusion of an ultrasound scan or in case of unfavorable results of biochemical screening, a geneticist may offer the expectant mother to undergo ... Depending on the period, it can be a chorionic or placental biopsy, amniocentesis or cordocentesis. Such a study gives highly accurate results, but in 0.5% of cases, such an intervention can cause a miscarriage.

Sampling of material for genetic research is carried out under local anesthesia and with ultrasound control. The doctor punctures the uterus with a thin needle and carefully takes the genetic material. Depending on the gestational age, these can be chorionic or placental villi particles (chorionic or placental biopsy), amniotic fluid (amniocentesis), or blood from the umbilical vein (cordocentesis).

The obtained genetic material is sent for analysis, which will determine or exclude the presence of many chromosomal abnormalities: Down syndrome, Patau syndrome, Evards syndrome, Turner syndrome (99% accuracy) and Klinefelter syndrome (98% accuracy).

” Four years ago, an alternative to this method of genetic research appeared - a non-invasive prenatal genetic test. This study does not require obtaining genetic material - it is enough for it to take blood from the vein of the expectant mother for analysis. The method is based on the analysis of DNA fragments of the fetus, which, in the process of renewing its cells, enter the bloodstream of the pregnant woman.

You can do this test from the 10th week of pregnancy. It is important to understand that this test is still not widely used in Russia, very few clinics do it, and not all doctors reckon with its results. Therefore, you need to be prepared for the fact that the doctor may strongly recommend an invasive examination in case of high risks of ultrasound or biochemical screening. Whatever it was - the decision always remains with the parents-to-be.

In our city, non-invasive prenatal genetic tests are performed by clinics:

    Avicenna. Panorama test. Non-invasive prenatal genetic diagnosis of aneuploidies 42 tr. Non-invasive prenatal genetic diagnosis of aneuploidies and microdeletions - 52 tr

    Almita. Panorama test. The cost is from 40 to 54 tr. depending on the completeness of the study.

    "Ultrasound studio". Prenetix test. The cost is 38 tr.

Expert opinion

Only chromosomal analysis can confirm or exclude chromosomal abnormalities. Ultrasound and biochemical screening can only calculate the magnitude of the risk. Analysis for pathologies such as Down syndrome, Edwards and Patau syndrome can be performed from 10 weeks of pregnancy. This is done by obtaining fetal DNA directly from the structures of the ovum (direct invasive method). The risk arising from invasive intervention, in the presence of direct indications, is guaranteed to be lower than the risk of chromosomal pathology (approximately 0.2-0.5% according to different authors).

In addition, today any pregnant woman of her own free will be examined for the presence of major genetic diseases in the fetus by a direct non-invasive method. To do this, you just need to donate blood from a vein. The method is absolutely safe for the fetus, but quite expensive, which limits its widespread use.

Difficult decision

The question of whether a diagnosis of genetic diseases during pregnancy is necessary and what to do with the information obtained as a result of research, each woman decides for herself. It is important to understand that doctors have no right to put pressure on a pregnant woman in this matter.

Expert opinion

With a gestation period of up to 12 weeks, a woman herself can decide on the need to terminate a pregnancy if any fetal pathology is detected. At a later date, good reasons are needed for this: pathological conditions incompatible with the life of the fetus and diseases that will subsequently lead to profound disability or death of the newborn. In each case, this issue is resolved taking into account the duration of pregnancy and the prognosis for the life and health of the fetus and the pregnant woman herself.

There are two reasons doctors may recommend terminating a pregnancy:

    fetal malformations have been identified that are incompatible with life or with the prognosis of deep disability in the child;

    a condition of the mother in which prolongation of pregnancy can cause an unfavorable course of the disease with a threat to the life of the mother.

Prenatal diagnosis - be it biochemical, ultrasound, or genetic testing - is optional. Some parents want to have the most complete information, others prefer to limit themselves to a minimum set of examinations, trusting nature. And every choice is worthy of respect.

Even a healthy woman can have a baby with genetic disorders. Pregnant women need to donate blood for chromosomal abnormalities to exclude this possibility. Laboratory tests are carried out for all women, but there are also strict indications in which the gynecologist gives a referral for a blood test.

The analysis time is limited by a clear framework. During pregnancy, every two to three weeks, a woman takes various tests: blood, urine, smear, and others. All these studies cannot show abnormalities in the development of the fetus. Special tests for various pathologies of the child are taken at 10-12 weeks of pregnancy. Such tests consist of ultrasound and blood tests for chromosomal abnormalities. Each woman can pass them at will. Again, with a positive result of the first examination, it is prescribed to donate blood and undergo an ultrasound scan for future mothers at 16-18 weeks.

Who needs to be tested without fail

In some cases, a blood test is assigned to expectant mothers in the following situations:

  1. The age of a pregnant woman is from 30-35 years.
  2. Parents are close relatives.
  3. If the fetus died in a pregnant woman or the child was stillborn.
  4. If a woman already has a child (children) with a pathology.
  5. The pregnant woman had a history of miscarriages, premature birth.
  6. The expectant mother, shortly before the onset of pregnancy, suffered a bacterial or viral pathology.
  7. The pregnant woman took illegal medications.
  8. One of the parents was x-rayed, that is, was exposed to ionizing radiation.
  9. Certain results of ultrasound diagnostics have been obtained, which require a more thorough check.
  10. The family lives in an ecologically unfavorable area or the parents of the unborn baby work in hazardous chemical production.

Abnormalities at the chromosomal level that help identify this analysis include the following syndromes:

  • Down;
  • Edwards;
  • Patau;
  • de Lange.

In addition, thanks to laboratory research, it is possible to determine pathologies such as a defect in the neural tube and a violation in the work and structure of the heart muscle.

Preparing to donate blood for analysis

The expectant mother must prepare for the examination without fail.

The preparation period lasts several days and consists in excluding for 3-4 days from your diet:

  • fatty, smoked, fried foods;
  • hot spices;
  • limit salt;
  • oranges, chocolate, coffee, eggs, red vegetables and fruits.

Attention! Food should not be taken on the day of blood sampling, and fluid intake should be limited. Drinking is allowed 4 - 6 hours before the start of material collection to determine the pathology of the fetus.

Features of delivery of analysis

In the collection of material for possible fetal pathologies there is nothing terrible and difficult. A laboratory assistant takes blood from a vein and transfers this material to geneticists for research. Doctors study the chromosomes found in the blood, taking into account the physiological characteristics of a woman. If abnormalities are found, the data is entered into the computer. After processing the indicators, a result is obtained, which indicates the likelihood of the unborn child's illness.

After receiving computer results for chromosomal pathologies, genetics decipher the analysis, compare the results with computer diagnostics and draw conclusions about the presence or absence of various disorders in the baby.

In addition to taking blood to detect abnormalities, pregnant women must undergo an ultrasound examination at 10-14 weeks. Ultrasound allows you to assess the structure of the unborn child, as well as the size of the nasal bone and TVP. In babies without disturbances, the nasal bone is clearly visible, and the thickness of the collar space ranges from 3 mm or more. With such an examination, the gestational age and the size of the fetus must be taken into account.

At 20-22 weeks of pregnancy, a second ultrasound is performed, which allows you to determine the pathology of the heart system, brain and other parts of the baby's body.

What to do if a baby has a pathology

With a positive result about the presence of violations in the baby, doctors suggest making a more reliable analysis:

  • take blood from the umbilical cord;
  • take amniotic fluid material.

Studies of these materials provide more accurate information about the presence or absence of developmental disorders of the child. If the likelihood of pathologies is confirmed and the identified defects turn out to be incompatible with the baby's life, then the woman is offered to terminate the pregnancy.

Today medicine has made great strides forward and some of the detected developmental disorders can be corrected. So, for example, a heart defect can be eliminated by surgery in the first days of a child's life.

Genetic abnormalities cannot be corrected.

Therefore, what to do: terminate the pregnancy or give the baby a chance to be born - this decision remains with the expectant mother.