How to prepare for karyotype analysis. Carrying out a blood test for a karyotype to determine possible chromosomal disorders. Where to do the analysis

When getting married, everyone dreams of a happy long life surrounded by their beloved children. However, the happiness of becoming parents, unfortunately, is not available to everyone. There are many reasons for infertility, and genetic disorders are far from the last among them. Therefore, in developed countries, determining the karyotype of spouses is a mandatory procedure for those wishing to enter into a marriage union.

As we remember from biology, a karyotype is a description of chromosomes in somatic cells (their number, shape, size and structural features). A person can be the owner of sections of rearranged chromosomes without even knowing it. The problem will emerge only when trying to conceive, because a defect in chromosomes at times increases the risk of a missed pregnancy, miscarriage, or the birth of a child with genetic diseases.

Of course, changing the karyotype of spouses for the better is impossible. But, knowing about the causes of infertility or abortion, you can find ways to resolve this problem. For example, turn to the program of artificial insemination. Moreover, taking into account the high risk of the birth of unhealthy offspring, there is always the opportunity to use donor biomaterial (eggs or sperm).

Karyotyping

Karyotyping, karyotype study or cytogenetic analysis is a procedure designed to identify deviations in the structure and number of chromosomes that can cause infertility or hereditary diseases in an unborn child.

Every organism has a specific set of chromosomes called a karyotype. A distinctive feature of the human karyotype is 46 chromosomes (44 autosomes - 22 pairs that have the same structure in the female and male body, and a pair of sex chromosomes). Women have two X chromosomes (46XX karyotype), while men have one X chromosome and one Y chromosome (46XY karyotype).
Each of the chromosomes carries the genes responsible for heredity, and karyotyping, in turn, allows you to detect hereditary diseases that are directly related to changes in the karyotype (failures in the chromosome set, the shape of the chromosomes, defects in individual genes). These diseases include syndromes: Down, Patau, Edwards; syndrome "cat's cry". Such diseases are found in people who have inherited the 47 karyotype, which has one extra chromosome in its set.

Today, two main methods for studying the karyotype are used:

1. Analysis of chromosomes of blood cells of those who applied (cytogenetic examination);

2. Prenatal karyotyping (analysis of fetal chromosomes).

A cytogenetic examination makes it possible to detect such cases of infertility or miscarriage, when the chance of offspring is sharply reduced in one of the spouses, and sometimes it is completely absent. In addition, it is possible to detect cases of a significant increase in genome instability, and then special treatment with antioxidants and immunomodulators to some extent will reduce the risk of conception failures.

Prenatal karyotyping (karyotyping) makes it possible to determine the chromosomal pathology of the fetus at the earliest stages of pregnancy. And this is very important, because the disappointing figures of medical statistics say that out of 350 male newborn babies, one necessarily has a 47XX karyotype or a 47XY karyotype, which entails all concomitant diseases. Do not think that newborn girls do not suffer from genetic diseases. Turner's syndrome, which causes the 45 X karyotype, like other diseases, is also quite common.

• chromosomal pathology in the family or clan;
• miscarriage;
• the age of the pregnant woman is over 35 years (for 30 births - 1 case of genetic pathology);
• assessment of mutagenic effects (chemical, radiation or other).

Cytogenetic examination of future parents

To analyze the chromosome set, blood is taken from patients, highlighting lymphocytes. Then they are stimulated in a test tube, forcing them to divide, and a few days later the culture is treated with a special substance that stops cell division at the stage when chromosomes are already visible. From the cells obtained in culture, smears are prepared on glass, which are then used for research.

Obtaining additional information about a possible change in the karyotype, gives the use of a special color, as a result of which all chromosomes receive a specific transverse striation. When the karyotype and idiogram (systematizing the image of a set of chromosomes) are obtained, the analysis procedure begins.

The geneticist examines 11 or 13 cells under a microscope to reveal a change in the karyotype (chromosome set), trying to detect quantitative and structural inconsistencies. For example, in Turner syndrome, which is manifested by short stature, structural features of the face and female infertility, a 45X karyotype is detected, i.e. There is one X chromosome and not two, as is normal.

In Klinefelter's syndrome, characterized by male infertility, on the contrary, there is an extra X chromosome, which will be expressed by a 47XX karyotype. In addition, structural disorders of the chromosomes themselves are revealed, such as: inversion - rotation of a chromosome segment by 180 °; deletion - loss of parts of chromosomes, translocation - transfer of fragments of one chromosome to another chromosome, etc.

Prenatal diagnosis

This set of procedures is an intrauterine examination of a child before birth, aimed at identifying hereditary diseases or malformations. There are several types of this study.

1. Non-invasive methods. They are completely safe and involve an ultrasound examination of the fetus and the identification of certain biochemical markers from the blood of a pregnant woman.

2. Invasive methods, which involve a controlled "invasion" of the uterus, in order to take material for research. So it is possible to accurately determine the change in the karyotype of the fetus and warn of possible concomitant pathologies (Down syndrome, Edwards syndrome, etc.)

Invasive procedures include: chorion biopsy, amniocentesis, placentocentesis, cordocentesis. Why, for the purpose of research, the cells of the chorion or placenta, amniotic fluid or blood taken from the umbilical cord of the fetus are taken.

The implementation of invasive procedures has the risk of complications, so they are carried out only according to strict indications:

• age limit (women over 35);
• children already born in the family with a change in the karyotype or malformations;
• carriage by parents of chromosomal rearrangements;
• change in the level of biochemical markers (PPAP, hCG, AFP);
• detection of pathologies during ultrasound of the fetus.

Invasive diagnostics is also carried out if there is a high risk for the fetus to develop a gene disease or determine the sex of the baby in diseases whose inheritance is associated with sex (for example, hemophilia, which a mother can only pass on to her sons).

All invasive procedures are carried out only by experienced specialists in a day hospital and under ultrasound control. After the manipulations, the pregnant woman will be under observation for a couple of hours. In order to prevent possible complications, a woman is prescribed certain drugs. The obtained fetal cells are analyzed by molecular methods in order to detect changes in the karyotype and identify specific gene diseases.

Today, this method makes it possible to diagnose 300 out of 5 thousand known hereditary diseases, such as hemophilia, phenylketonuria, cystic fibrosis, Duchenne muscular dystrophy and others.

The most cherished desire of both parents is the birth of a healthy, physically and mentally healthy child. Unfortunately, there are a number of indicators that significantly increase the risk of developing various fetal pathologies.

Many couples face challenges when deciding to have children. It can be infertility, habitual miscarriages, miscarriages or the birth of a child with genetic abnormalities. In these cases, to determine the cause of the pathologies, karyotyping of the spouses is recommended before pregnancy planning.

This is a new cytogenetic study that studies the set of human chromosomes (karyotype). Thanks to him, a geneticist can determine how spouses match each other at the gene level and whether the risk of pathology in the development of their unborn baby is high.

Indications for the procedure

Although this method is gaining popularity every year, many couples are poorly versed in what karyotyping is and are apprehensive about the need for it. Elementary knowledge of genetics will help clarify.

A karyotype is a set of chromosomes in the human body that determines its features: height, body structure, intelligence level, eye and skin color. The normal human karyotype is 46 chromosomes, of which 2 are responsible for gender differences. Certain abnormalities in the karyotype lead to genetic diseases. Thus, the presence of only one extra chromosome causes an incurable disease known as Down syndrome.

It is likely that in the future, all married couples will undergo analysis for the conformity of spouses at the gene level. So far, doctors prescribe a study only in certain cases. A comparative analysis of chromosomes makes it possible to determine with almost absolute certainty the likelihood of violations in an unborn baby.

The set of chromosomes of a woman (left) and a man (right)

Main indications for karyotyping:

• parents are over 35 years of age;
• frequent miscarriages, couple infertility for unknown reasons;
• the presence in the immediate family of one or both parents of hereditary diseases;
• close relationship of a married couple;
• repeated attempts at artificial insemination, which were unsuccessful;
• hormonal imbalance in women, bad in men;
• prolonged contact of spouses with harmful chemicals;
• living in environmentally unfavorable conditions;
• smoking, uncontrolled intake of potent drugs, alcohol abuse, drug addiction of potential parents;
• the presence of a child with congenital malformations in a married couple.

The cytogenetic method of karyotyping is enough to carry out once. It allows you to identify potential risks of fetal pathologies, even in cases where hereditary diseases do not appear for several generations. The study is recommended to be carried out at the stage of pregnancy planning.

How the analysis is carried out

Blood cells are examined to determine the karyotype. To exclude the negative influence of various factors, careful advance preparation for the analysis is necessary.

Not later than two weeks before the procedure, it is necessary to stop taking medications, especially antibiotics, to exclude alcoholic beverages and smoking. If at least one of the spouses has an acute infectious / viral disease or an exacerbation of a chronic illness, the analysis should be postponed.

For research, venous blood is taken from both spouses.

The turnaround time for karyotyping is approximately three weeks. During this time, geneticists monitor the state and division of cells. For a more reliable determination of the structure of chromosomes, they are stained. Next, the stained material is compared with the norms of cytogenetic schemes of chromosomes.

The results allow you to determine the presence of a third extra chromosome in a pair, the absence of a chromosome or part of it, duplication or displacement of chromosomes. The procedure will help to find out how changes in the genes affect the formation of blood clots, as well as to detect a gene mutation, the elimination of which will help reduce the likelihood of severe cystic fibrosis.

Karyotyping reveals the risk of developing Down syndrome, Patau, Edwards, Ternar, Klinefelter. In addition, a genetic predisposition to the development of myocardial infarction, diabetes mellitus, and hypertension is determined.

Only an experienced geneticist can decipher the data obtained. It is unacceptable to draw any conclusions to persons without medical education!

After the results show good compatibility of the spouses, you can proceed to pregnancy planning without fear. No additional procedures or analyzes are required. If deviations are found, the doctor may prescribe a course of treatment, and in severe cases, recommend using either sperm.

When is fetal karyotyping necessary?

If the study of the genetic material was not carried out before the onset of pregnancy, and the woman is already carrying a child, fetal karyotyping can be performed. Most often, the need for such a procedure occurs with an unplanned pregnancy and the presence of risk indicators.

Analysis is assigned in the following cases:

• mother's age exceeding 35 years;
• suspicion of fetal pathology during ultrasound;
• deviations from the norm of blood tests;
• the presence of a child with a disease caused by genetic disorders in a married couple;
• past drug use or alcohol dependence of the mother;
• transferred viral disease in the first three months of pregnancy;
• contact of one of the parents with harmful chemicals, long-term residence or work in an environmentally unfavorable area.

Many women are wary of this analysis, believing that it can harm the unborn child. Indeed, the question of whether prenatal karyotyping is dangerous remains relevant.

Methods

The best period for conducting a study of the gene material is the first three months of bearing a child. Most gene pathologies are successfully identified at an early stage. In modern medicine, there are two methods: invasive and non-invasive.

• The non-invasive method of karyotyping does not pose a danger to the unborn baby. It provides for ultrasound and a biochemical blood test. But his results are not always accurate.
• The invasive method is considered more informative. It shows fairly reliable results, the percentage of errors is minimal. To determine the state of the chromosome set, karyotyping of the chorion, taking a sample of amniotic fluid () and blood from the umbilical cord () will be required. The study of possible gene anomalies is carried out similarly to the blood test of the parents.

A prerequisite for an invasive research method is to inform parents about possible risks to the fetus. In some cases, bleeding may open, placental abruption and even miscarriage may occur.

How important is karyotyping with aberrations?

Aberrations are certain chromosomal abnormalities that can be either regular or irregular. A simple study will not give complete information. His main normal result is 46XY (male karyotype) and 46XX (female karyotype).

Women with, after several unsuccessful attempts at artificial insemination, are shown only karyotyping with aberrations, which will reveal abnormalities in the chromosome set.

Deviation detection: what to do?

Since this study is a very complex and time-consuming process, it can only be entrusted to an experienced geneticist in a medical center with an excellent reputation. After receiving the results, the doctor conducts a special consultation for parents, during which he acquaints them with the degree of probability of having a child with developmental anomalies.

In some cases, the prescribed drug and vitamin therapy can significantly reduce the likelihood of developing disorders in the formation of the fetus.

If a child is diagnosed with genetic pathologies, doctors, informing the parents about this, may offer to terminate the pregnancy. This is another reason why karyotyping is best done in the first trimester. However, the final decision on whether to keep the child or not, only the parents have the right.

How much can you trust this genetic study, and are there possible errors in karyotyping?

Experts say that the probability of an error in the results of a procedure performed in a specialized medical clinic is less than 1%, so future parents can be confident in the reliability of the results.

Karyotyping is an analysis to detect chromosomal abnormalities, which is carried out to determine abnormalities in the number and structure of chromosomes. This research method may be included in the general list of examinations that are assigned to couples before planning conception. Its implementation is an important part of the diagnosis, since the results make it possible to identify chromosomal abnormalities that interfere with conception, pregnancy and cause severe abnormalities in the development of the fetus.

For analysis for karyotyping, both venous blood (sometimes cells of the bone marrow or skin) of the parents, and fragments of the placenta or amniotic fluid can be used. It is especially important to perform these at high risks of transmitting chromosomal pathologies to an unborn child (for example, if one of the relatives is diagnosed with Edwards, Patau, etc.).

What is a karyotype? Who is eligible for karyotyping? How is this analysis done? What can he reveal? You will receive answers to these and other popular questions by reading this article.

What is a karyotype?

A karyotype is a set of chromosomes in a human cell. Normally, it includes 46 (23 pairs) of chromosomes, 44 (22 pairs) of them are autosomal and have the same structure, both in the male and in the female body. One pair of chromosomes differs in its structure and determines the sex of the unborn child. In women, it is represented by XX chromosomes, and in men - XY. The normal karyotype in women is 46,XX, and in men it is 46,XY.

Each chromosome is made up of genes that determine heredity. Throughout life, the karyotype does not change, and that is why you can take an analysis to determine it once.

The essence of the method

To determine the karyotype, a culture of cells taken from a person is used, which is examined in vitro (i.e., in vitro). After the selection of the necessary cells (blood lymphocytes, skin cells or bone marrow), a substance is added to them for their active reproduction. Such cells are kept in an incubator for some time, and then colchicine is added to them, which stops their division in metaphase. After that, the material is stained with a dye that visualizes the chromosomes well, and examined under a microscope.

Chromosomes are photographed, numbered, arranged in pairs in the form of a karyogram and analyzed. Chromosome numbers are assigned in descending order of their size. The last number is assigned to the sex chromosomes.

Indications

Karyotyping is usually recommended at the stage of conception planning - this approach minimizes the risk of having a child with hereditary pathologies. However, in some cases, this analysis becomes possible after the onset of pregnancy. At this stage, karyotyping allows you to determine the risks of inheriting a particular pathology or is performed on fetal cells (prenatal karyotyping) in order to identify an already inherited developmental anomaly (for example, Down syndrome).

• spouses are over 35 years of age;
• the presence in the family history of a woman or a man of cases of chromosomal pathologies (Down syndrome, Patau, Edwards, etc.);
• prolonged absence of conception for unexplained reasons;
• planning;
• previously performed unsuccessful IVF procedures;
• bad habits or taking certain medications in a future mother;
• hormonal imbalance in a woman;
• frequent contact with ionizing radiation and harmful chemicals;
• the presence in the anamnesis of women of spontaneous abortions;
• stillborn child in history;
• the presence of children with hereditary diseases;
• episodes of early infant mortality in history;
• caused by disorders in the development of spermatozoa;
• marriage between close relatives.

• anomalies in the development of the fetus;
• deviations of psychomotor or psycho-speech development in combination with microanomalies;
• congenital malformations;
• mental retardation;
• growth retardation;
• deviations in sexual development.

How is the analysis carried out?

• alcohol intake;
• taking certain medicines (especially antibiotics);
• acute infectious diseases or exacerbation of chronic pathologies.

Blood sampling from a vein for analysis is performed in the morning in a state of satiety of the patient. It is not recommended to take biomaterial on an empty stomach. When taking tissue samples for fetal karyotyping, sampling is performed under ultrasound guidance.

How long to wait for the result?

The result of karyotyping can be obtained 5-7 days after the delivery of the material for research. During this time, specialists monitor cell division in the incubator, slow down their development at a certain point, analyze the material obtained, combine the data into a single cytogenetic scheme, compare it with the norm, and draw up a conclusion.

What can karyotyping reveal?

The analysis allows you to determine:

• shape, size and structure of chromosomes;
• primary and secondary constrictions between paired chromosomes;
• site heterogeneity.

The results of karyotyping according to the generally accepted international scheme indicate:

• the number of chromosomes;
• belonging to autosomes or sex chromosomes;
• features of the structure of chromosomes.

The study of the karyotype allows you to identify:

• trisomy (or the presence of a third chromosome in a pair) - is detected with Down syndrome, with trisomy on the 13th chromosome, Patau syndrome develops, with an increase in the number on the 18th chromosome, Edwards syndrome occurs, with the appearance of an extra X chromosome, Klinefelter's syndrome is detected;
• monosomy - the absence of one chromosome in a pair;
• deletion - lack of a chromosome segment;
• inversion - reversal of a section of a chromosome;
• translocation is the movement of segments of a chromosome.

Karyotyping can detect the following pathologies:

• chromosomal syndromes: Down, Patau, Klinefelter, Edwards;
• mutations that provoke increased thrombosis and premature termination of pregnancy;
• gene mutations, when the body is unable to detoxify (neutralize toxic agents);
• changes in the Y chromosome;
• propensity to and;
• propensity for.

What to do if deviations are detected?

When abnormalities in the karyotype are detected, the doctor explains to the patient the features of the detected pathology and talks about the nature of its impact on the life of the child. Particular attention is paid to incurable chromosomal and gene anomalies. The decision on the advisability of maintaining pregnancy is made exclusively by the parents of the unborn baby, and the doctor only provides the necessary information about the pathology.

If a tendency to develop certain diseases (for example, myocardial infarction, diabetes mellitus or hypertension) is identified, attempts can be made to prevent them in the future.

Karyotyping is the analysis of a set of chromosomes in a person. This study is carried out by examining blood lymphocytes, bone marrow cells, skin, amniotic fluid or placenta. Its implementation is shown at the stage of conception planning, but if necessary, the analysis can be carried out during pregnancy (on samples of cells from the parents or the fetus) or to an already born child. The results of karyotyping make it possible to detect the risk of developing chromosomal and genetic pathologies and to identify predisposition to certain diseases.

One of the most modern diagnostic methods is a genetic blood test. This study allows you to identify a person's predisposition to the development of various hereditary diseases. An analysis for a karyotype reflects changes in a person's chromosome set. The study is very much in demand today, as it allows you to determine the discrepancy in the sets of chromosomes of the husband and wife before conceiving a child.

Definition

What is a karyotype? This is the set of chromosomes of each person. Each person has an individual set of chromosomes, which may differ in their number, size and shape, and other characteristics. Normally, the number of chromosomes is 46. 44 of them are responsible for the external similarity of the parents and the child. They determine the color of the hair, eyes, skin, the shape of the ears and nose, and so on. Only 2 chromosomes are responsible for sex.

When to take a test

Karyotyping is done only once in a lifetime, because the set of chromosomes and their characteristics cannot change with age. This study is assigned to spouses with problems with conceiving and bearing a child.

Today, young people are increasingly taking this test on their own before planning a pregnancy.

A feature of genetic analysis for a karyotype is to assess the risks of having a baby with genetic abnormalities and diseases. Also, the analysis can reveal the causes of miscarriage or infertility of one of the spouses.

Medical indications for the study are:

• The age of one of the spouses is more than 35 years old when planning pregnancy.
• Inability to conceive a child for unknown reasons.
• Ineffective IVF operations.
• The presence of a genetic disease in a husband or wife.
• Hormonal failure in a woman.
• Failure in the maturation of spermatozoa.
• Accommodation in an unfavorably ecological area.
• Chemical poisoning or exposure of one of the spouses.
• Bad habits in a woman.
• Multiple miscarriages.
• Marriages between relatives.
• Having a child with a genetic disorder.

How the study is done

Preparation for analysis is not difficult for patients. Karyotype analysis is not carried out on an empty stomach; you can eat before blood sampling. It is only necessary to stop taking antibiotics 7 days before the sampling. Blood is taken from the patient's vein. After that, with the help of special equipment, mononuclear leukocytes are eliminated from the blood. After that, cells capable of dividing are introduced into the blood. At a certain stage, the specialist evaluates the result, photographs it and makes an opinion.

Usually, the result of the karyotype analysis can be obtained no earlier than 14 days later.

The form from the laboratory will contain information about the number of chromosomes in the patient and their deviations in various parameters, if any.

Many couples are interested in where to take a karyotype test. If the analysis is prescribed for you by a doctor, you can do it at a family planning center. You can also apply there for voluntary research. In addition, the analysis is done at the institutes of genetics and other specialized institutions. The local clinic does not provide this service. The cost of analysis can vary from 5000 to 8000 rubles. depending on the completeness of the information.

How to decrypt

Only a geneticist can decipher the analysis. The results of the analyzes of a married couple are carefully analyzed. After that, the doctor can give an opinion on the causes of your problems with conceiving or on the risks of having a child with abnormalities. What can modern karyotype analysis show? The breakdown of the analysis shows the following risks and deviations:

• Mosaicism.
• Translocation assessment.
• The absence of one of the fragments of the chromosome.
• Absence of one of the paired chromosomes.
• The presence of an extra chromosome.
• The unfolding of one of the fragments of the chromosome chain.
• Gene mutations that lead to abnormalities in the newborn.

In addition, depending on the karyotype, it is possible to determine a person's predisposition to such diseases as:

• Myocardial infarction.
• Stroke.
• Diabetes.
• Hypertension.
• Arthritis, etc.

As a result, the norm is 46XY in men, 46XX in women. In children, the possible deviations are as follows:

• 47XX + 21 and 47XY + 21 - the child has an extra chromosome in the 21st pair, which is evidence of Down syndrome.
• 47XX + 13 and 47XY + 13 - such children are born with Patau syndrome.

There are a number of other deviations. Some of them are dangerous, others not so much. Only a doctor can determine the real risks of having an unhealthy child in each individual case. If dangerous mutations are detected, it is better to terminate the pregnancy.

What to do if deviations are found

In order to prevent the birth of a child with gene mutations, it is better to donate blood for analysis even before pregnancy. This is especially true for those couples in which the wife or husband is over 40 years old.

If abnormalities are found, the doctor will explain the risks to you.

When the test is done on a woman who is already pregnant, if a gene disorder is found, the woman may be asked to terminate the pregnancy. However, the decision to give birth or not remains with the parents. No one has the right to insist on an abortion. However, you should not immediately panic if you have gene disorders. Many of them do not affect the health of the child. With such anomalies, you just need to carefully monitor the pregnancy and follow all the doctor's recommendations.

Every married couple should carefully plan the birth of children. If for some reason you are assigned an analysis to determine the karyotype, you must definitely do the indicated test. It is better to donate blood for research even before pregnancy or in the first weeks after conception. Parents should not be faced with the question of how much the analysis costs, because the birth of a healthy child is much more expensive than any money.

In contact with

Violations in the structure of chromosomes may not manifest themselves in any way during life. But when the egg and sperm merge, two genetic sets meet, and then an unsuccessful match of genes can cause a miscarriage or the formation of a congenital pathology in the fetus. Karyotyping of spouses helps to identify abnormalities in the structure and number of chromosomes, as well as the likelihood of a particular deviation.

Karyotype examination is an optional analysis. The procedure has its own indications, including miscarriages and missed pregnancy in history. Reproductive problems associated with the peculiarities of genetics are quite rare.

Karyotyping is a diagnostic procedure that detects abnormalities in the structure and number of chromosomes. Such deviations can cause hereditary pathologies in a child and infertility of spouses.

Each person has their own specific set of genes, which is called a karyotype. Chromosomes are arranged in pairs: 22 pairs of autosomes and 1 pair of sex chromosomes, which are represented as XX in the female body, and XY in the male body. They consist of genes - sections that are responsible for the manifestation of a particular trait.

Karyotyping detects diseases that are directly related to changes in DNA. The defect can be in any gene, in the structure of chromosomes or their number. The most famous example is Down syndrome, also called trisomy 21.

Karyotyping of spouses (cytogenetic analysis) is a study of the chromosomes of blood cells. The procedure reveals the causes of miscarriage or infertility in couples when other factors are already excluded (hormonal, immune, infectious). If increased genome instability is detected, the use of antioxidants and immunomodulators will help reduce the risk of conception failures.

Which couples are indicated for karyotyping?

As already noted, karyotyping of spouses is not included in the list of mandatory diagnostic procedures. It is shown in the following cases:

1. One or both parents are over 35 years old.
2. Infertility, the causes of which cannot be determined by other methods.
3. Several unsuccessful IVF procedures.
4. Living in areas with poor environmental conditions, working in hazardous industries, contact with hazardous chemicals.
5. Smoking, alcohol abuse, taking drugs, certain medications.
6. Previous miscarriages, miscarriages, premature births.
7. The spouses are blood relatives.
8. Previously born children with genetic diseases.

Preparation for the examination procedure

The analysis is carried out in a laboratory and does not pose any danger to the health of the spouses. 2 weeks before the procedure, you must stop drinking alcohol, tobacco products and medications. If the intake of any medication cannot be canceled, the laboratory assistant must be warned about this.

Blood sampling is carried out on a full stomach, the last meal should occur 1-2 hours before the analysis. Before the procedure itself, you need to fill out a special questionnaire or bring it with you (in some cases, it is filled out by the doctor in advance). If the karyotyping of spouses coincided in time with an exacerbation or acute course of an infectious disease in one or both of the couple, then the study should be rescheduled.

Conducting an analysis

In karyotyping, blood is taken from a vein. The laboratory assistant fills a test tube with it and releases the patient. It usually takes about 5 days for genetic analysis and preparation of results.

For further research, only a part of the material is needed - lymphocytes. They are isolated from the blood during the period of division. In order to provoke the activity of this process, special drugs are added (Colchicine, Nocazadol). Over the next three days, the features of cell reproduction are analyzed. Based on the results obtained, a conclusion is made about possible pathologies and risks of abortion.

Modern technologies allow karyotyping using only 15 cells and special preparations. Therefore, one blood sampling is enough to obtain accurate and complete information about chromosomes and genes.

What will give the result?

Interpretation of the analysis for karyotyping of spouses is carried out by a geneticist. The normal result for women is 46XX, for men - 46XY. It means that a total of 46 chromosomes were found, the last pair of which is sexual. When a genetic pathology is detected, this formula changes. For example, with Down syndrome (trisomy on chromosome 21), it looks like 46XX21+.

The result of karyotyping helps to determine the following pathologies:

1. Trisomy is the presence of an extra third chromosome in a pair. Trisomy on the 21st chromosome - Down syndrome, on the 16th - spontaneous miscarriage in the 1st trimester, on the 13th - Patau syndrome, on the 18th - Edwards syndrome. Of these, the only viable option is Down syndrome.
2. Monosomy is the absence of one chromosome from a pair. Monosomy of any autosomal chromosome leads to early death of the embryo. A similar pathology in couple XX in women is manifested by Shereshevsky-Turner syndrome.
3. A deletion is the absence of a part of a chromosome. If large areas are lost, early death of the embryo occurs. In other cases, genetic pathologies (for example, crying cat syndrome with a deletion of the 5th chromosome) or a positive effect on viability (for example, HIV resistance) may develop. Deletion of the sex chromosome in men is the cause of impaired spermatogenesis and leads to infertility.
4. A duplication is the presence of a duplicate fragment of a chromosome. The functions of the original genes are not affected.
5. An inversion is a 180° rotation of a part of a chromosome. Some of these changes are normal, while others lead to the death of germ cells and the formation of unbalanced material in them. The result is reduced fertility, increased risk of miscarriage and fetal abnormalities.
6. Translocation is the movement of a segment of a chromosome. Some of these changes do not affect the person in any way, the other leads to miscarriages, congenital fetal anomalies (Robertsonian translocations).

The results form records changes in the structure of chromosomes. The long shoulder is denoted by the letter "q", the short one - "t". For example, cat's cry syndrome (deletion on the 5th chromosome) is written as follows: 46XX5t or 46XY5t.

The second thing that is found during karyotyping is changes in genes. Can be identified:

1. Gene mutations that affect blood clotting. Increased thrombus formation can cause miscarriage, infertility, or the inability to implant a fertilized egg.
2. Mutation of genes in the Y chromosome is the cause of male infertility, requiring the use of donor sperm.
3. Gene mutations that reduce the body's ability to detoxify - get rid of harmful substances obtained from the external environment.
4. Changes in the gene for cystic fibrosis, leading to the occurrence of this disease in a child.

Identified deviations from the norm: what to do?

To obtain complete information about the results of karyotyping, the spouses need to come for a consultation with a geneticist. He will tell you in detail about the possible risks and the likelihood of developing a particular violation.