What does the chromosomal abnormality of the fetus mean? The causes of malformations. Spontaneous abortion, including habitual abortion

30.04.2019

Biochemical screening during pregnancy - this word is called the analysis of venous blood, in which special hormones are determined, which are markers of the chromosomal pathologies of the fetus. It is the results of this examination that determine, without being a diagnosis, how high the risk of malformations in a growing fetus is. This is what a biochemical examination in the "interesting period" is, and it should only be carried out in conjunction with an ultrasound examination at the same time.

Do pregnant women need biochemical screening?

The study can be carried out for all women who want to be sure that their child will be born healthy (meaning, without a chromosomal pathology that cannot be treated). But there are also strict indications, given which the gynecologist of the antenatal clinic gives directions for biochemical screening. These are the following situations:

future parents are close relatives
there was already a stillbirth or the pregnancy was frozen in this woman
mother over 35
there is already 1 child with some kind of chromosomal abnormality
for a long time there is a threat of spontaneous miscarriage
there was a single or repeated case of miscarriage or premature spontaneous birth
the pregnant woman has suffered a viral or bacterial pathology during or shortly before pregnancy
it was necessary to take medications that were not allowed for pregnant women
before conception, someone from a married couple was exposed to ionizing radiation (x-rays, radiation therapy)
dubious results of ultrasound diagnostics in relation to malformations.

Perinatal diagnostics for hormone content is carried out only in conjunction with the performance of a screening ultrasound scan during pregnancy.

What pathologies are determined by the study of the blood of pregnant women

These are such diseases:

Edwards syndrome
neural tube defect
Down syndrome
Patau syndrome
de Lange syndrome

Syndromes Edwards, Patau and Down are united by the common name "trisomy". Moreover, each cell contains not 23 pairs of chromosomes, but 22 normal pairs and 1 "triplets". In which pair the "trinity" was formed, the disease is called.

For example, if screening for Down is performed, then there are three (not two) 13 chromosomes (the syndrome is written as "Trisomy 13"). These conditions must be identified prior to 3 trimester screening.

Preparing for the analysis for chromosomal abnormalities

Preparation for the diagnosis of the 1st trimester for markers of chromosomal diseases is that the day before the study, you exclude from the diet:

spicy food
fatty and fried foods
smoked meats
chocolate
citrus.

How is a biochemical blood test carried out

How to donate blood for biochemistry. You come with the results of ultrasound screening for 1 trimester on an empty stomach in the laboratory in the morning, sit down to the nurse, who collects a small amount of blood from a vein for you.

The results of a genetic study of the 1st trimester are issued after 1.5 weeks or a little more. When donating blood from a vein for 16-20 weeks, it will be necessary to wait a little longer, since the second screening during pregnancy involves the study of three or four hormones in the blood (in the first trimester, two hormones are determined - a "double test").

Data decryption table

Perinatal biochemical diagnostics of the 1st trimester consists of the definition of chorionic gonadotropin (hCG) and a protein called PAPP-a. The level of these hormones differs depending on the gestational age:

But this result is greatly influenced by the age of the pregnant woman and her weight. Therefore, such a solution was invented (this applies not only to the biochemical study of the 1st trimester, but also to the second).

A large number of women living in the area were selected, they were divided by age and body weight in order to select the average indicators of hormones. The average result obtained for each hormone was called the median (MoM).

With the help of MoM, the decoding of the blood test for the 1st trimester is carried out: if your personal result when dividing by this average is 0.5-2.5 of these conventional units (they are called MoM), then the hormone level is normal. Low - if less than 0.5 MoM, high - respectively, above 2.5.

According to the MoM method, the decoding of the diagnostic study of the 2nd trimester is also carried out, and the norms will be the same. Perinatal biochemical diagnostics of the 2nd trimester assesses the levels of three or five hormones already. It:

Chorionic gonadotropin (its norm at 16-20 weeks is 10-35 thousand IU / ml)
PAPP-A (its rate differs at different times)
Unconjugated estriol
Inhibin A
Placental lactogen.

Risks of chromosomal abnormalities

After this blood test of both the first and 2 trimesters, the program calculates the risks of a particular syndrome. To do this, compare your hormone level with a certain number of pregnant women with the same level of the same hormone.

The final results of perinatal blood tests look like this: the risk for each identified pathology is described as a fraction and the words "high" (this is bad), "medium" or "low".

A risk of 1: 380 or higher is called high (1: 100 is extremely high). Average - 1: 1000 or below (the norm for biochemical screening of the 1st and 2nd trimester). Low - below 1: 10000. This number after the fraction means that out of a certain (for example, 10 thousand) pregnant women with such a level, for example, hCG, only 1 develops Down syndrome.

With risks of 1: 250-1: 380, a woman is sent for medical genetic counseling, repeated ultrasound and biochemical screening, only in the conditions of the Perinatal Center or genetic counseling.

What affects the calculation of risks

High weight: hCG and PAPP increase in overweight women, on the contrary in thin women.
Pregnancy happened as a result of IVF.
I had amniocentesis during this week.
Pregnancy is multiple.
The mother suffers from diabetes.

In these cases, "sifting" may not even be carried out, since its results are unreliable.

Some features in the analyzes for pathology

Prenatal screening for trisomies includes the assessment of hormones (at the first screening - two, at the second - three to five) in relation to the development of:

Down syndrome
Patau syndrome
Edwards syndrome.

These three pathologies are the most common disabling trisomies.

Consider the screening for Down syndrome as the most common one. In the case of a high risk of this particular pathology, such changes are noted with 1 screening:

at 11 weeks, the nasal bone is not visible in 70% of diseased fetuses
thickened collar space
high levels of hCG.

In the second trimester, it is revealed that the AFP level is low, and hCG is high.

If the program also gives a result for this pathology below 1: 380, the pregnant woman is recommended to undergo invasive diagnostics to confirm the diagnosis: amniocentesis or cordocentesis. Until then, the diagnosis is not made.

Thus, biochemical screening during pregnancy is a blood test, thanks to which one can only suspect the development of one or another chromosomal pathology in an intrauterine fetus. Based on the results of this study, the diagnosis is not made.

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 tests (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 in 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 only helps the woman to make this difficult decision.

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, Ph.D.

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 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 conclusion, 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 defects in chromosomes (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.

The sampling of material for genetic research is carried out under local anesthesia and under 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 fetal DNA fragments, 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. Cost 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 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 at her own request can be screened 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 it is quite expensive, which limits its widespread use.

Difficult decision

The question of whether the 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.

What are chromosomal abnormalities?

It is a type of genetic condition caused by major changes in the genetic material. In most cases, they are found in children with multiple birth defects or complex problems that develop from the moment of birth.

What are chromosomes?

Chromosomes are structural formations in all cells of the human body that store genetic information, large elements of deoxyribonucleic acid (DNA). A person normally has forty-six chromosomes.

What features of appearance make you suspect the presence of chromosomal abnormalities of the fetus?

These features can be as serious as missing eyes or heart abnormalities, or less severe, such as misaligned ears or short fingers. The specific features of chromosomal developmental abnormalities depend on which particular chromosome is involved.

How does this pathology develop?

In most cases, chromosomal abnormalities of pregnancy occur when the egg or sperm are formed. Sometimes chromosomal changes occur shortly after conception in the early stages of embryonic development. In rare cases, a chromosomal abnormality in children is inherited from one of the parents. In this case, the parent himself either has or does not have a similar problem.

What research is needed to make an accurate diagnosis?

The most common test is an analysis for the presence of chromosomal abnormalities, or karyotype. It is carried out using a blood sample that is sent to the cytogenetics laboratory (chromosomes are examined in it). The laboratory processes the sample, photographs the chromosomes, counts and examines them carefully. Lab technicians are looking for significant changes in chromosomes, such as a missing or extra element. But this test does not detect small changes in the genetic material. Chromosome analysis for abnormalities takes ten days to two weeks.

Investigation of small elements of genetic material allows fluorescent in situ hybridization - FISH method (assigned depending on the specific characteristics of the child), as well as a new method - analysis of DNA microarrays (in some cases, it is preferable to the FISH test).

What kind of complications can result from chromosomal abnormalities?

If a child has a physical abnormality, such as the absence of a hand or foot, all complications will be associated with it. Most of the diseases associated with chromosomal abnormalities entail mental retardation, which can be quite significant. Serious chromosomal abnormalities associated with severe changes in genetic material lead to death in infancy or childhood.

Are chromosomal abnormalities treatable?

The risks of chromosomal abnormalities are not treatable. There is no way to extract the abnormal chromosome and put the normal one in its place. However, your child will receive the necessary treatment. The specific type of treatment (physiotherapy, heart surgery) is determined based on the needs of your baby.

Is it possible to give birth to our next child with the same pathology?

If a child has a disease due to a chromosomal abnormality, both parents are usually examined. If both chromosomes are normal, the risk of having another child with pathology is not higher than usual. (The risk is always present.) If a parent has a chromosomal abnormality, the chance of having a child with the abnormality is at least fifty-fifty. Depending on the specific chromosome abnormality, the likelihood of the development of pathology in the next child may be two out of three.

Should we seek advice from a geneticist or other specialist?

Yes. Your child should be seen by a doctor who specializes in genetics. They can help you arrange the test and tell you what to expect from a child with a chromosome disorder. With him, you can discuss the likelihood of developing a similar pathology in the next child, markers of chromosomal abnormalities and get contact details of other families where there are children with the same problems.

What special childcare regimen should we follow when we return home?

Your child with a chromosome disorder will need traditional pediatric care. If he needs special care, such as tube feeding, you should be trained in the hospital. In some cases, children with chromosomal abnormalities do not live very long. You may decide to enroll your child in a hospice. Hospice programs support both the child and the parent to ensure that the family has an adequate quality of life, even if the baby is short-lived.

When is it worth re-showing the child to the doctor in connection with the disease and the presence of a chromosomal abnormality?

Your child is likely to have frequent checkups and physical therapy. He may need surgery. Your pediatrician will help arrange visits to all doctors.

Angela Scheuerly, M.D., geneticist.

The normal course of pregnancy and the excellent health of a young woman are not yet a guarantee of a healthy baby without anomalies. It is important, even in the early stages of pregnancy, to carry out the necessary diagnostic measures to identify or exclude chromosomal pathology. Environmental factors, heredity, maternal condition and other less common reasons can provoke an anomaly of intrauterine development.

What is a chromosomal abnormality? This is the appearance during intrauterine development of an extra chromosome or a violation of its structure. Everyone is familiar with Down syndrome, so this congenital disease is associated with an extra chromosome in 21 pairs. It is possible to identify this pathology even before birth due to the clinical picture, characteristic diagnostic signs, and the nature of the course of pregnancy.

Signs of chromosomal abnormalities during pregnancy

A chromosome abnormality occurs quite often in a child who has been affected by adverse factors during intrauterine development. This applies to the woman's lifestyle, her state of health, the environment.

You can suspect congenital pathologies, including an extra 21 chromosome, by the following signs:

pulling pains in the lower abdomen during the entire period of pregnancy, the threat of miscarriage;
decreased fetal activity, increased fetal kidney at 20-21-22 weeks;
underdevelopment of the tubular bones of the fetus;
underdevelopment of the placenta, fetal hypoxia;
polyhydramnios or low water.

These concomitant manifestations of pregnancy may indicate an anomaly, but an analysis is needed to confirm, since each of the presented abnormalities of pregnancy may indicate other violations, and in some cases even be the norm. But why does a chromosomal failure occur and is it possible to prevent it?

Causes of chromosomal abnormalities

Late pregnancy is a risk factor

The risk factors for the development of congenital anomalies are too diverse and it is physically impossible to track all the components. This is an environmental factor that cannot be influenced, and problems that arise even in the process of fertilization, when an abnormal appearance or disappearance of another chromosome occurs during the joining of 46 chromosomes. The process is quite complex, and it is impossible to trace it from the very beginning, that is, from the moment of conception.

The most common pathology is the appearance of an extra 21 chromosome, one of the types of trisomy, when a chromosome has three copies. For example, people with Down syndrome have three copies of chromosome 21.

It often happens that a fetus with a chromosomal abnormality does not survive, an early miscarriage occurs. But those who survive are born with serious physical and mental problems.

Diagnosis of chromosomal abnormalities

Today, it is not a problem to identify an extra 21 chromosome even before birth, as well as other abnormalities. For this purpose, an analysis of the chromosome set is carried out, by taking blood after the birth of a child or by examining the chorion. The cells that were obtained through a biopsy are grown in a laboratory, after which they are analyzed for the presence of an extra 21 chromosome or the absence of some of the chromosomes in the set.

Geneticists recommend this analysis to every woman in order to know for sure the possibility of chromosomal pathology in the unborn child. This analysis can be carried out regardless of the woman's age and gestational age, but the analysis efficiency is high and in 99% it is possible to carry out an accurate analysis of the chromosome set.

The first stage of diagnosis begins with taking the mother's blood in the first trimester of pregnancy, and an ultrasound scan is also performed to visually examine the fetal neck, which has diagnostic value in suspicion of an extra 21 chromosome - Down's syndrome. In the second trimester of pregnancy, the mother's blood is also tested, during this period, the greatest risk of a chromosomal abnormality can be determined.

Women who are at risk should undergo an additional analysis - a chorea biopsy is performed to make a diagnosis.

Frequent chromosomal abnormalities

The first place is occupied by trisomy 21 chromosomes - Down's syndrome. This congenital disorder is diagnosed in 1 in 700 babies. Such children lag behind in mental development, have specific external signs, characteristic facial features and are more susceptible to systemic diseases than healthy children.

Children with Down syndrome have limited intellectual potential, but at the present stage, activities are being carried out aimed at the socialization of such children, they can further study and engage in activities that do not require serious physical and intellectual needs. Previously, the intervention of psychologists, psychotherapists and other specialists makes it possible to improve the prognosis of the development of children with an extra 21 chromosome, they begin to write, read and take an active part in collective activities.

The risk of having a child with a chromosomal abnormality increases in proportion to the mother's age. Thus, women under 25 give birth to a child with a chromosomal disorder 1 in 15,000, and women after 45 years - 1 in 40. The difference is significant, and therefore the main risk group is older age.

The second most common abnormality is trisomy 13 and 18 chromosomes - these abnormalities are much more serious than Down's syndrome, and very often such children do not survive. If a woman was analyzed and the result showed these abnormalities, the doctor will suggest an abortion at an early stage of pregnancy, since the chances of bearing and giving birth are minimal.

Children born with trisomy 13 - Patau syndrome and trisomy 18 - Edwards syndrome suffer from severe physical and mental disabilities. Each child has a pronounced external developmental defect, and they live no more than a year.

Sex chromosome abnormalities - Turner syndrome, trisomy on the X chromosome, Klinefelter syndrome and disomy on the Y chromosome occur when 23 pairs of chromosomes are abnormal.

Turner syndrome - occurs in 1 in 3,000 girls born. Such girls do not go through the stage of puberty, they do not have a second X chromosome, they are infertile. Such girls stop growing early if hormone therapy is not started from an early age. Adequate hormonal treatment can only partially restore sexual function, but they cannot return the possibility of having a child with any drugs.

Other chromosomal pathologies associated with a violation of 23 pairs of chromosomes occur very rarely, and all those born with this anomaly lack reproductive function.

Rare chromosomal abnormalities

Some chromosomal abnormalities are so rare that their analysis does not show at all or shows, but a completely different violation. These include deletion, inversion, translocation, ring chromosome, and microdeletion. This is a series of chromosomal abnormalities that develop due to diseases on the part of the mother.

Rare chromosomal pathologies can occur against the background of maternal diabetes mellitus, diseases of the endocrine system, smoking and other bad habits. Every woman after 35 years old is tested to determine chromosomal abnormalities, as well as girls under 16 years old. The course of pregnancy, previous infectious diseases, intrauterine infections or toxic effects on the fetus are of great importance.