Features of karyotyping when planning a child

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When starting a family, people most often dream of the future appearance of healthy and full-fledged children. No matter how hard you try, it is not always possible to get pregnant, carry a pregnancy to term, and give birth to a healthy baby. This may be due to genetic disorders of one or both spouses. Moreover, none of them could have previously guessed about the existence of this type of problem with their health. After all, an incorrect set of chromosomes is not always accompanied by some external defects. Modern medicine, using karyotyping of spouses, allows not only to identify abnormalities and diseases, but also helps to avoid the occurrence of further complications associated with them, including during the period of planning and carrying a pregnancy.

What it is

Karyotyping is a method of cytogenetic diagnostics, the essence of which is the study of human chromosomes. During the diagnosis of the chromosome set (karyotype), it is possible to determine changes in the numerical composition and detect violations of the structure of chromosomes.

Karyotyping must be performed once in a lifetime. Thanks to him, it is possible to determine the mismatch of spouses' chromosomes. This may be the fundamental factor in the birth of a baby with a developmental defect or a severe form of genetic disease, due to which the spouses cannot have a child.

How the study is carried out: types of diagnostics

To study the karyotype, venous blood is taken and lymphocytes that are at the stage of division are isolated from it. This test requires only 12–15 lymphocytes. They are placed in a test tube and observed for growth and division for 3 days. To stimulate proliferation, mitogen is added, and to fix mitosis, colchicine is added to the test tube.

There are two types of karyotyping – classical and spectral. For classical karyotype diagnosis, chromosomes are stained with various dyes:

• Q – staining with quinine mustard with further examination under a fluorescent microscope. Used to study the Y chromosome: determining genetic sex, detecting translocations, mosaicism in the Y chromosome.
• G – used most often in cytogenetic analysis. Detects small aberrations and marker chromosomes.
• R – acridine orange dye. Colors those areas that are not amenable to Q and G dyes.
• C – used for centromere analysis.
• T - used to study telomeres.

The second method of cytogenetic research is called the spectral karyotyping method, or fluorescence hybridization. Chromosomes are stained with fluorescent dyes, which are deposited on specific areas of the chromosomes. This diagnostic method makes it possible to determine interchromosomal translocations, because the translocated areas will differ in spectrum from the other chromosome.

Geneticists insist that a married couple undergo diagnostic tests when planning a pregnancy. If the woman is already pregnant, fetal karyotyping is performed. Material for fetal karyotyping is collected in the early stages of gestation. To extract blood from the umbilical cord, the invasive method of cordocentesis is used. The prenatal examination itself is painless, but doctors monitor the woman and fetus for several hours after the puncture.

Main reasons for conducting analysis

Karyotyping is a fairly common procedure in European countries. But in Russia this analysis began to be practiced not so long ago, although the demand is increasing every year. The main task of this diagnostic method is to determine the compatibility between spouses, which will allow one to conceive a child and give birth to him without pathological changes and various abnormalities.

In most cases, such an analysis is performed in the first stages of planning a child, although it is possible to perform it on a woman who is already pregnant. In this case, material is collected from the fetus and mother. This will allow you to determine the quality of the chromosome set. Naturally, karyotyping is not a mandatory manipulation for young parents, but it will be able to timely detect many pathologies in a baby who has not yet been born.

When performing an analysis, you can understand the predisposition of the future baby to diabetes and hypertension, heart attacks and other pathological processes of the joints and heart. When collecting material, a defective pair of chromosomes is determined, which will allow one to calculate the risk of having an unhealthy child.

Karyotyping for frozen pregnancy

If the doctor has determined that the pregnancy is frozen, karyotyping is recommended when removing the fetus from the uterus. This will help to understand the reason that led to the cessation of fetal development, and will also be useful when contacting a geneticist in the process of planning a subsequent pregnancy.

To determine the karyotype of the fetal material, karyotyping can be performed in the following ways:

• The standard cytogenetic method is effective if there are disturbances in the number of chromosomes or their structure. However, when conducting such a study, living cells are needed, therefore, if the fetus froze for a relatively long time, conducting the study in this way will be impossible;
• Fluorescence hybridization is carried out in the case of a minimum number of living cells in the abortive material. This method will allow us to study only some of the chromosomes, but in the vast majority of cases it is the anomalies of their development that lead to the emergence of pathologies incompatible with life;
• Comparative genomic hybridization of the matrix type is a high-resolution study that is carried out if the first two types are unsuccessful. Its use makes it possible to identify the smallest anomalies, which allows for tactical planning for the next pregnancy.

Information based on the results of fetal karyotyping will determine which chromosomal abnormalities provoked the cessation of development.

Indications for karyotyping

Ideally, all spouses who dream of becoming parents should undergo karyotyping. Moreover, this must be done even if there are no conditions for diagnostics. Most hereditary diseases that grandparents had may not make themselves felt, but karyotyping will allow you to identify an abnormal chromosome and calculate the risk of a baby having diseases.

Mandatory indicators for carrying out manipulation are:

1. Age of the spouses. If they are over 35 years old, then this is already a reason to get tested.
2. Infertility that has an unknown origin.
3. Numerous and unsuccessful attempts to get pregnant using IVF.
4. The presence of a hereditary disease in one of the spouses.
5. Hormonal imbalance in a woman.
6. Impaired sperm production for an unknown reason.
7. Negative environmental conditions.
8. Contact with chemical components and irradiation.
9. The influence of harmful factors on a woman’s body: smoking, drugs and alcohol, taking medications.
10. Spontaneous abortion or premature birth.
11. A marriage between relatives.
12. When the family already has a child with chromosomal pathologies and congenital malformations.

Manipulation, which involves diagnosing the karyotypes of spouses, should be carried out at the stage of pregnancy planning. The possibility of performing karyotyping during pregnancy should not be ruled out. Then the diagnosis will be performed not only on spouses, but also on the unborn child. This procedure is called perinatal karyotyping.

Which couples are recommended for karyotyping?

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

1. One or both parents are over 35 years of age. Read more about the risks of late pregnancy→
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, missed pregnancies, premature births.
7. Spouses are blood relatives.
8. Previously born children with genetic diseases.

What does the analysis reveal?

The procedure uses a unique technology for collecting material, thanks to which it is possible to separate blood cells and isolate the genetic chain. Without any problems, a geneticist will be able to determine the percentage of development of the risk of trisomy (Down syndrome), the absence of one chromosome in the chain, the loss of a genetic section, as well as duplication, inversion and other genetic pathologies.

In addition to identifying the presented deviations, you can see various kinds of anomalies that can cause the development of various serious deviations during fetal development. They can cause a gene mutation that is responsible for the formation of blood clots and deoxidation. Timely identification of the presented deviations allows you to create normal conditions for the development of the child and prevent miscarriage and premature birth.

How to decrypt

For representatives of the stronger sex, the normal karyotype analysis results are 46, XY, and for women - 46, XX. The number 46 indicates the normal number of chromosomes, and the X and Y at the end indicate the shape, structure and size of a healthy person - these indicators differ for men and women. Based on the test results, the doctor will make several notes on the form. Their decoding will help you understand medical terms:

1. Translocation - a chromosome rearrangement has occurred. If the patient has a balanced translocation, then it most likely will not manifest itself. If unbalanced, serious deviations are possible.
2. Mosaicism - cells with genetic characteristics different from normal are found.
3. Trisomy – this pathology occurs most often; the patient has an extra chromosome. The most common occurrence is the appearance of a copy of chromosome 21, leading to diseases such as Down syndrome.
4. Inversion - a section of a chromosome is rotated 180 degrees.
5. Monosomy is only one of the pairs of homologous chromosomes in a genotype.
6. Deletion – a fragment of a chromosome is lost.

Preparation for karyotype analysis of spouses

The analysis in question is performed in laboratory conditions and is completely safe for men and women. If a woman is already pregnant, then material is collected from the existing fetus. Blood cells are taken from the spouses, and then, using various manipulations, the chromosome set is determined. Then the quality of existing chromosomes and the number of gene pathologies are determined.

If you decide to undergo the karyotyping procedure, then you should stop smoking, drinking alcohol and taking medications for 14 days. If there is an exacerbation of chronic and viral diseases, then diagnosis will have to be postponed to a later period. The duration of the procedure is 5 days. Lymphocytes are isolated from biological fluid during the division period. Over the course of 3 days, a complete analysis of cell proliferation is performed. It is based on the results of this division that we can draw a conclusion about the pathologies and risks of miscarriage.

Since unique technologies are used today, to obtain accurate results it is necessary to use only 15 lymphocytes and various drugs. This means that spouses will not need to go several times to donate blood and other biological fluids. It is enough for a married couple to perform the analysis once, and based on its results they can already plan conception, pregnancy and the birth of healthy children.

There are situations when pregnancy is already taking place, but the necessary diagnostics to detect the abnormality have not been carried out. For this reason, genetic material will be collected not only from the fetus, but also from the parents.

It is best to get tested in the first trimester of pregnancy, because it is during this period that it is very easy to identify and establish such ailments as Down Syndrome, Turner Syndrome and Edwards Syndrome. To ensure that the fetus does not experience any harmful effects when collecting material, diagnostics are performed using an invasive or non-invasive method.

The non-invasive method remains a safe method of obtaining results. It involves performing an ultrasound, as well as a blood test on the mother in order to determine various markers. The most accurate results can be obtained by performing the analysis using an invasive method, but it is also very risky. Using special equipment, procedures are performed in the uterus, thanks to which the necessary genetic material can be obtained.

All manipulations do not cause pain in the woman and fetus, but after diagnosis using an invasive method, inpatient observation is required for several hours. Such manipulation can cause a threat of miscarriage or missed pregnancy, so doctors warn their patients about all the consequences and possible risks.

Basics of genetics

Any living organism consists of cells, in their nuclei there are chromosomes - nucleoprotein structures that store and transmit hereditary information from generation to generation.

In almost every human cell, in the absence of pathologies, there are 46 chromosomes, or otherwise 23 pairs.

They are divided into:

• Autosomal (22 pairs). These chromosomes contain information about skin, eye and hair color, height, level of intellectual development and other hereditary data;
• Genitals (1 pair). In a female type karyotype, both chromosomes in a pair are identical and are designated XX. The male karyotype contains one equal-armed X chromosome and another rod-shaped Y, so the sex chromosomes in boys are designated XY.

At the moment of conception, the embryo receives an equal number of chromosomes from the mother and father, and during the transfer of sex chromosomes from a man, Y or X can pass, which determines the sex of the unborn child.

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The risk of transmitting genetic abnormalities is possible if both the father and mother have abnormalities, since the fetal karyotype consists of maternal and paternal chromosomes.

What to do if deviations are detected?

Whenever the result of the analysis is received, the specialist invites the spouses to his place to announce the likelihood of having an unhealthy baby. If the compatibility of a man and a woman is impeccable, then the chromosome set has no deviations, then the doctor tells the spouses all the stages of pregnancy planning.

If specific abnormalities have been discovered, then the doctor’s task is reduced to prescribing a course of therapy that can help prevent the development of unpleasant complications when planning to become parents. But, when deviations become known already during pregnancy, parents may be advised to get rid of it or the right of choice is left to them.

In such a situation, every parent can take a risk and give birth to a full-fledged healthy baby, but the doctor is obliged to warn about all sorts of deviations and their consequences. When planning a child, everyone can use the donor's genetic material. A geneticist and gynecologist cannot legally force a woman to have an abortion, so the choice always remains with the parents. Children are the meaning of every person’s life. So it is necessary to approach the process of planning and conception with all responsibility. It is good that today there is such a manipulation as karyotyping, thanks to which it is possible to prevent unpleasant complications during fetal development.

Possible complications for the fetus after karyotyping

The non-invasive examination method is absolutely safe and does not cause any complications, but is less informative than the invasive one.
When carrying out the second method there is a small risk (2-3%). Such a study is indicated in cases where the benefit justifies the risk, that is, there is a real threat of having a baby with severe chromosomal abnormalities.

The worst consequences are miscarriage, bleeding or leakage of amniotic fluid. Therefore, before the procedure, the doctor must inform you about possible dangers.

Modern science does not stand still. Thanks to narrow examinations, it is possible to identify possible DNA abnormalities and the compatibility of spouses at the genetic level, which is important when planning children.

With or without aberration: distinctive features

Karyotyping without aberrations is performed by the method of assessing qualitative and quantitative abnormalities of the chromosomal set of all cellular structures of the human body. Quantitative changes include anomalies in the number of chromosome pairs, but qualitative changes include anomalies in the structure of the chromosomes themselves.

With this manipulation, it is possible to identify cellular changes that can be transmitted from parents during conception or in the first 7 days of the formation of the fertilized egg. They become the basis for the development of the child’s body.

Karyotyping with aberrations is an addition to the classical procedure. In this case, it is possible to detect irregular aberrations that characterize the effect of negative environmental factors on the body of one of the parents. This method is more informative by analogy with the previous one.

What is aberration and for what reasons does it occur? These are deviations in the structure of chromosomes that arise as a result of the rupture of their structures, and then redistribution, loss or doubling occurs.

Aberrations can be quantitative (the number of chromosomes changes) and qualitative (the structure changes). They can occur in all cells of the body (regular) or be present only in certain cells (irregular). The formation of regular ones occurs in the first days of pregnancy, in irregular ones - after the influence of negative environmental factors on one of the parents.

With karyotyping, the doctor makes a verdict on the possibility of successfully conceiving a child. But sometimes, as a result of diagnosis, chromosomal pathologies are also determined. Irregular aberrations are almost impossible to detect, and to detect them, manipulation is performed only during pregnancy.

Mechanism

Preference is given to venous blood, which is taken from both spouses. Lymphocytes that are in the mitosis (division) phase are eliminated from the venous blood. Within three days, cell growth and reproduction are analyzed, for which lymphocytes are treated with a mitogen, which stimulates mitosis. During the division process, the researcher can observe the chromosomes, but the process of mitosis is stopped by special treatment. Then special preparations of chromosomes are prepared on glass.

To better reveal the structure of chromosomes, they are stained. Each chromosome has its own individual striations, which becomes clearly visible after staining. Then the stained smears are analyzed, during which the total number of chromosomes and the structure of each are determined. In this case, the striation of paired chromosomes is compared, and the result obtained is compared with the norms of the cytogenetic patterns of chromosomes.

The analysis usually requires no more than 12-15 lymphocytes; this number of cells makes it possible to identify quantitative and qualitative chromosome mismatches, and, consequently, a hereditary disease.

Price

Karyotyping is an expensive research method. Not every couple can afford it. The cost of the test depends on whether only the parents will donate blood or whether material will also be collected from the fetus, as well as on the location of the clinic. Approximate price:

• diagnostics of the karyotype of one patient—4500-7500 rubles;
• blood test for karyotype with images of chromosomes - 5000-8000 rubles;
• karyotyping with detection of aberrations (blood with heparin) is a more informative diagnosis, but its price is higher - from 5500-6000 rubles;
• karyotyping with detection of aberrations with images of chromosomes - from about 6,000 rubles.

Karyotyping is an important and necessary diagnostic method for those who want to give birth to a healthy and healthy child. The essence of the technique is to identify in advance the existing genetic abnormalities in parents and direct all efforts to eliminate them.

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January 17, 2018

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Indications for the purpose of the study

1. A history of 2 or more spontaneous miscarriages. 2. Infertility. 3. Oligozoospermia. 4. Non-obstructive form of azoospermia. 5. Primary (or secondary) amenorrhea. 6. Frozen pregnancy. 7. Cases of infant mortality in the first year of life or the birth of a dead child in the family. 8. The birth of a child with congenital combined defects. 9. Delayed development of the baby (both physical and mental. 10. Genetic diseases in parents and close relatives. 11. Suspicion of genetic pathology based on existing external signs (for example: a specific shape of the skull, fingers, abnormalities of the external genitalia, eyes, nose, etc.) 12. Examination of donors of genetic material.