Preimplantation genetic diagnosis of embryos. How is pre-implantation diagnostics carried out? How is the study going

Women who go to IVF do not always have a good idea of ​​the main stages of this technique. And when a doctor is interested in whether the patients would like to undergo pre-implantation diagnostics, there are even more questions. Some refuse, having learned that PGD leads to an increase in the cost of the protocol, others simply do not know for what purpose such a genetic study is prescribed and whether it is necessary at all. In this article we will tell you what PGD in IVF is and what it can tell you.

PGD ​​- what is it?

Since the fusion of a woman's egg with a man's sperm, everything has been predetermined at the genetic level - the hair color of the unborn child and its growth, intellectual abilities and gender, as well as possible genetic anomalies and diseases that the child inherited from parents, grandparents or other relatives ...

Preimplantation diagnostics is a complex of genomic studies that allows you to identify in an embryo that is only a few days old, various developmental abnormalities, diseases, syndromes and other troubles. PGD ​​is able to identify about 150 hereditary genetic ailments, among which are quite common - Down syndrome, Turner, and quite rare - cystic fibrosis, hemophilia, butterfly wing syndrome, etc.

With the help of special techniques and high-precision equipment, diseased embryos are identified and screened out. For transplantation into the uterine cavity, women use only high-quality, healthy and viable embryos.

Standard IVF does not include the mandatory stage of preimplantation diagnosis. After fertilization and cultivation of embryos for several days, only the growth rate, cleavage rate, and the viability of embryos are assessed. After that, they are transferred to the woman's uterine cavity. Which of them will take root and whether they will take root at all is a big question. The efficiency of standard IVF is about 35%.

If pre-implantation diagnostics is carried out, then future parents may not worry about the state of the baby's health, even if they themselves have certain genetic problems. In addition, the effectiveness of IVF with PGD is slightly higher - about 40-45%. This is due to the fact that a large embryo, even when implanted into the uterus, has very little chance of development and survival. A healthy and examined embryo is more likely to successfully establish itself and begin to grow and develop.

The purpose of the survey

PGD ​​is highly recommended for parents who have genetic diseases that can be inherited by their toddler. Also, such a preliminary genetic examination of embryos will not hurt if there were hereditary ailments in the ranks of close relatives of future parents.

Diagnosis before implantation is important and necessary for couples in which one of the parents is a carrier of the disease linked to the sex chromosome. For example, a woman carries the hemophilia gene, but the child will be sick only if it is a male baby. PGD ​​in this case determines the sex of embryos, which are only a few days old, and doctors select for replanting only those embryos that are not threatened by hemophilia, that is, girls.

For a woman with a negative Rh factor and several pregnancies in the past (it does not matter how they ended), PGD is recommended if the husband's sperm with a positive Rh factor was used for in vitro fertilization. In this case, doctors will select from all the resulting embryos only those who inherited the maternal Rh identity. In this case, pregnancy after IVF will proceed with lower risks, and the baby will not be threatened by a dangerous hemolytic disease.

PGD ​​is recommended for a couple in the event that a woman has had two or more miscarriages earlier, if there have been cases of a frozen pregnancy, and also if any of the spouses in their first marriage or have already had a child with chromosomal abnormalities together, or genetic pathologies. Diagnosis before transfer allows excluding those who are sick or have abnormalities of non-genetic origin from the number of embryos considered for transplantation.

Preimplantation diagnostics in the second or third IVF protocol allows to establish with high accuracy the reasons for unsuccessful previous attempts.

And a completely non-standard, but alas, a real situation - parents go to IVF to give birth to a baby who can become a donor, for example, bone marrow, for their own older brother or sister. In this case, relying on natural conception is too risky. The born child may not be suitable as a donor for a sick relative.

Pre-implantation diagnostics will help to select individuals from the resulting embryos with a certain combination of genetic information that guarantees genomic matching between children. This study is called HLA typing.

What does the survey show?

Preimplantation genetic diagnosis allows you to identify in advance various diseases and conditions in which a child may be unviable or disabled. It all depends on what recommendations the geneticist gives. If necessary, embryos are examined only for certain criteria and gene mutations; in general, it is possible to assess all the parameters determined by research.

So, PGD with an accuracy of 97-99% determines blindness and deafness, congenital deafness, retinoblastoma, Fanconi anemia, neurofibromatosis, phenylketonuria, myopathy, torsion dystonia, Duchenne muscular dystrophy and several dozen dangerous and incurable diseases and syndromes.

Also, PGD determines the karyotype of the embryo, its blood group and Rh factor, sex, the presence of mutations at the gene level, unusual for parents and manifested for the first time.

Who is appointed?

Because pre-implantation diagnostics in itself is not cheap. Not every woman who dares to undergo in vitro fertilization is recommended this additional stage. It is offered to everyone, but there are categories of patients for whom it is highly undesirable to abandon the preliminary genetic assessment of embryos before transfer to the uterus.

These patients include:

• "Age" women and couples. With age, the sex cells of men and women age and lose health. Under the influence of drugs, bad habits, unfavorable ecology and just past years, their DNA set can mutate. Therefore, “older” women and men have higher risks of fetal chromosomal abnormalities. PGD ​​is strongly recommended for women over 35 years old, as well as for couples in whom a man is over 40 years old.
• Rh negative women who had abortions, miscarriages, childbirth, children with hemolytic disease were born. Diagnostics is relevant only if the spouse has a positive blood Rh factor. If donor sperm is used, then the biomaterial of a man with a negative Rh factor is initially selected, then the probability of obtaining Rh-positive embryos is zero.
• Women who already have 1-2 unsuccessful IVF attempts in the absence of objective reasons (the protocols were carried out correctly and without complications, there are no endometriosis and other obstacles to implantation).
• If the sperm of a man with low quality indicators of spermogram is used for fertilization(teratozoospermia, azoospermia, asthenozoospermia). With natural conception, low quality sperm die, have no chance of fertilization, with IVF they may well fertilize an egg, because natural selection is disturbed, which can lead to the development of various pathologies in the fetus.

Types of diagnostics

There are several types of genetic diagnosis of embryos. They differ in terms of research, technical nuances, equipment and research methods. Let's list the main ones, without going into laboratory and genetic details:

• FISH Is a fluorescent hybridization method. This is a fairly standard study, the cost of which is low compared to other methods of preimplantation diagnosis. But its accuracy is also somewhat lower than that of other methods. This method is widely used in clinics in Russia, Ukraine and Belarus. Foreign clinics practically abandoned it due to the fact that more accurate studies appeared. The plus is that the research is fast - within a few hours. The downside is that many chromosomes are not even examined.
• CGH- a method of comparative genomic hybridization. A very expensive way. And both financially and temporarily. But the list of defined pathologies is greater than that of the above-described method, and the accuracy is immeasurably higher. Among other things, this method of diagnosis before replanting allows you to determine which embryos have a higher chance of implantation.
• PCR- method of polymerase chain reaction. Reveals the Rh-belonging of the embryo, its blood group, as well as a fairly large list of genetic problems. The study requires a mandatory preliminary examination of biological parents for genetic mutations. If a woman is implanted with a donor embryo or donor oocytes were taken for fertilization, the PCR method cannot be used.
• NGS- sequencing method. This is a modern way of carrying out pre-implantation diagnostics, which combines the best from all of the above. It gives the most complete picture of the state of health of the embryos, however, and its cost is higher than that of other methods.

How is the research going?

In order for embryologists and geneticists to have the opportunity to do PGD, a sufficient number of eggs must be obtained through preliminary hormonal stimulation. If it is less than 3-4, then preimplantation diagnosis is usually not performed. After the doctors "organize" the meeting of the eggs with the purified sperm, the development of the embryos is monitored for 2-5 days. Then the embryologist can select the most viable ones. On the fifth day, blastocysts already have about 200 cells. There is an opportunity, without prejudice to the embryo, to take about 5-7 cells from each embryo for genetic research.

For the collection of cells, modern high-precision lasers are used, a biopsy of the cell membranes is performed, and other methods are also used. The examination of the DNA strand provides comprehensive information about whether the embryo is healthy. After which it is recommended for transfer.

It all depends on how many embryos are planned to be examined, which method of the above will be examined.

To reduce costs, a couple can use the means of a quota, diagnostics is included in the list of services that can be provided under compulsory medical insurance, but in each clinic this issue should be clarified separately. Some do PGD at the expense of the budget, others do not.

Possible complications

As already mentioned, the material for the study of genetics is obtained by biopsy. Despite the state-of-the-art precision equipment, there is still a possibility of injury to the fetus during this procedure. Most often, "three days" are subject to injury. It should be noted that the probability of injury is quite low - about 3%, and the benefit from the study will be much greater. Otherwise, the complications with such IVF can be the same as with IVF in the standard protocol.

Any of the stages of in vitro fertilization can be associated with certain risks, and this cannot be avoided. It is important that all risks are low.

The couple needs to understand well that even modern and accurate devices, with which doctors of the highest qualification category work, do not guarantee 100% that the baby will be healthy. So, with extensive mosaicism, biological errors can occur, and a diseased embryo can be implanted in a woman. There is such a probability, but it is very small - no more than 0.05%.

PGD ​​(preimplantation genetic diagnosis) - examination of the embryo for chromosomal abnormalities and genetic diseases before transferring it to the uterine cavity. It is used for IVF and ICSI, when fertilization takes place outside the woman's body.

• What diseases can be detected with PGD
• Indications and timing of genetic diagnosis of the embryo
• Do I need to prepare for PGD?
• Embryo diagnostic technique
• Method safety
• Benefits of PGD
• Doctors performing PGD
• PGD ​​cost

Purpose of the procedure:

1. Preventing the birth of a child with genetic disabilities, which is especially important for high-risk families.
2. Improving the effectiveness of assisted reproductive technologies.
3. Reducing the risk of miscarriage or missed pregnancy.

What diseases can be detected with PGD

With the help of genetic diagnosis of the embryo, it is possible to prevent chromosomal diseases in the unborn child, such as:

• Patau syndrome (severe congenital malformations);
• Down syndrome (specific appearance, congenital defects, mental retardation);
• Shereshevsky-Turner syndrome (short stature, developmental anomalies, impaired formation of the genital glands, girls are ill);
• Edwards (gross developmental anomalies);
• Klinefelter's syndrome (boys get sick, breast enlargement, sexual dysfunction) and others.

And it is also possible to identify monogenic diseases (in the case when there is a high risk of inheriting a specific disease), for example:

• cystic fibrosis - a violation of the function of the glands of external secretion, the respiratory system and the digestive tract;
• sickle cell anemia - a violation of the structure of hemoglobin, anemia with corresponding symptoms;
• hemophilia A - deficiency of blood clotting factor and associated prolonged bleeding, life-threatening;
• Duchenne muscular dystrophy - progressive muscle weakness;
• and others (the list of studied monogenic diseases includes more than 100 items, consult your doctor about the possibility of preventing a specific disease).

As you can see, all diseases are severe, and most of them cannot be corrected: gross developmental anomalies lead to a disastrous result in a short time, other pathologies reduce the quality of life of the whole family. Therefore, with a high risk of such diseases in the family, the use of PGD in the IVF cycle is an important stage in planning the birth of a healthy child.

Indications and terms of performance

Preimplantation genetic diagnosis is performed if the couple has at least one of these factors:

1. The risk of genetic pathology - the spouses or their blood relatives have hereditary diseases.
2. The age of the mother at the time of IVF or ICSI is over 35 years old, and the age of the father is 39 years old.
3. Significant deviations in the spermogram.
4. The couple have had miscarriages and failed IVFs in the past. However, the reasons for this outcome were not identified.

Diagnostics is carried out at a certain time after fertilization:

Despite the need for a biopsy, no harm is done to the embryo, and the procedure itself does not affect the development of pregnancy. All cells at these stages are pluripotent, that is, they are able to develop further to a full-fledged organism.

Separately, it should be said about the study of polar bodies. These are the cells that are formed during the division of the female reproductive cell, contain the same set of chromosomes as the oocyte, and are subsequently absorbed. The advantage of this method is that the tissues of the embryo are not used, because the biopsy is performed before fertilization.

At what stage to carry out the genetic analysis of the embryo and for what diseases is determined by the geneticist after a number of preparatory procedures.

Do I need to prepare for PGD?

The specialist conducts research with a ready-made embryo, so the participation of the spouses is not required. Polar body analysis also involves collecting material in advance. Preparation in these cases consists in observing the general rules that exist for IVF and ICSI.

But if a couple has a high risk of chromosomal abnormalities, then the preparation is different. Namely: both the man and the woman must donate blood to determine the karyotype. This will make it possible to determine the set of analyzes for the genetic diagnosis of the embryo.

Methodology

The basis of genetic diagnostics is PCR (polymerase chain reaction), that is, analysis of cell DNA. It consists in recreating a copy of a piece of DNA using enzymes and studying it.

There is also a second method - fluorescent hybridization, when molecules capable of luminescence are fixed on DNA with the help of a probe. By examining the material under a fluorescent microscope, the exact number of chromosomes can be counted and structural pathology, if any, can be identified.

The final stage of preimplantation genetic diagnosis is the assessment of the structure of embryos and the selection of the best ones in terms of morphological characteristics.

Diagnostics lasts up to 1 to 30 days, depending on the IVF protocol and the PGD method.

All these procedures can also be carried out in a cryoprotocol: that is, first diagnostics, then freezing. The transfer is carried out in the next cycle. This approach allows replanting when the mother's body is no longer exposed to hormones for stimulation, which is beneficial for both the expectant mother and the child.

Method safety

During genetic diagnostics, there is no interference with the functioning of the body of the father and mother. The maximum that is required from the spouses is to donate blood from a vein. Therefore, in this regard, the method is absolutely safe.

The question of the safety of PGD for the embryo has also been deeply studied by scientists. On the basis of the studies carried out, the specialists came to the conclusion that the technique does not affect the risk of developing congenital malformations or other anomalies that may appear after birth. The procedure is carried out at a stage of development when the cells of the embryo have not acquired specific functions, so they can easily replace each other in the process of subsequent division.

Benefits of PGD

• there is no termination of pregnancy if there is a risk of giving birth to a child with a genetic pathology - this embryo is simply not used for transfer;
• a wide range of detected diseases;
• high sensitivity of the method;
• the possibility of determining the sex of the child, and thus excluding sex-linked diseases.

Blastomere biopsy

One cell (blastomere) is taken from the embryo with microsurgical instruments on the third day after fertilization.

Trophectoderm cell biopsy

From three to five cells are taken from the embryo from the trophoectoderm, which is the outer layer of the blastocyst. This manipulation is carried out on the 5-6th day of embryonic development. This test option more reliably reveals anomalies of the karyotype of embryos.

Oocyte polar body biopsy

This is the most favorable diagnostic option, but it can only be carried out with genetic abnormalities in the female line. The polar body is the part of the egg that is not directly involved in fertilization, but the genetic material in it is identical to the nucleus of the egg.

PGD ​​safety

Diagnostics is carried out at a very early stage, when all the cells of the embryo are still pluripotent, that is, a full-fledged organism can form from each of them.

All stages of preimplantation genetic diagnosis do not harm the health of the embryo, fetus and unborn child.

When a diagnostic sample is received, it is prepared in a special way. The cells are either placed in a buffer solution, or on a glass slide, where they are fixed in a special way.

What diseases can be detected

Diagnosis of monogenic mutations

The most common monogenic diseases are amyotrophy, cystic fibrosis, phenylketonuria, mucopolysaccharidosis, and hemophilia. If future parents know about the presence of a similar disease in their families, then they are shown IVF with preimplantation genetic diagnosis.

Diagnostics of chromosomal translocations

Chromosomal translocations are such changes in chromosomes when parts of two chromosomes are rearranged, as if swapping places with each other. If the exchange is balanced (that is, the rearranged parts of the chromosomes are equal in size), then patients with a similar anomaly do not outwardly differ from others. However, they have a high probability of miscarriage and the manifestation of genetic pathology in the offspring. The severity of changes in future children may vary depending on the size of the rearranged part of the chromosome. You can find out about the presence of such a disease only with a special examination. It is prescribed in the presence of multiple unsuccessful IVF attempts, with multiple miscarriages in history, or at the birth of a genetically ill child.

PGD ​​accuracy

Preimplantation genetic diagnosis has a low probability of error - from 3 to 5%. That is why a pregnant woman, after carrying out genetic diagnostics at the IVF stage, is in any case assigned to carry out combined prenatal screenings at the standard stages of pregnancy. If, according to the results of screening, a high risk of the presence of chromosomal abnormalities in the fetus is obtained, then the patient must be prescribed invasive prenatal diagnostics (chorionic biopsy or amniocentesis).

How much does PGD cost?

The price for conducting PGD varies from 50 to 110 thousand rubles.

And if this amount at the beginning seems large enough, then after analyzing the costs of nursing and lifelong care for a sick child, it becomes clear that this is a fairly acceptable and very profitable investment. After all, pregnancy after PGD often proceeds normally, and children are born healthy.

A child with a genetically determined disease will need constant care, treatment, additional devices and equipment for organizing his daily life for life, all this is hundreds of times higher than the cost of PGD.

It is better to check the cost of the examination either with the attending physician or by looking at the website of the AltraVita reproduction clinic in the section “Prices”. Thus, we can confidently assert that the price of preimplantation genetic diagnostics is the health of the unborn child.

The cost of pre-implantation diagnostics of embryos is not so huge that it would have to be abandoned. Your baby's health is of much greater value. IVF with PGD is not only an opportunity to timely identify a mutation if it is present, but also to gain confidence that your unborn child is healthy if the result is negative.

Take the chance that IVF - PGD gives you! Its price is not so high. Remember that you have an advantage over women who become pregnant naturally because they cannot do preimplantation diagnostics. You also have the opportunity to check the embryo as part of IVF. With PGD, the cost will be a little more, but it's worth it!

Indications for PGD of the embryo

Preimplantation diagnosis of embryos is not always carried out only according to indications for IVF. A married couple can do PGD on their own initiative if they want to know for sure that their baby will be born healthy. PGD ​​with IVF will save future parents from unnecessary worries.

There are also indications for PGD. IVF in some cases involves the mandatory use of preimplantation diagnostics. The need for this procedure is determined by the doctor who performs IVF.

PGD ​​is carried out according to the following indications:

• The age of women is over 34 years old, and men - 39 years old;
• A history of more than two unsuccessful IVF attempts;
• A history of more than two miscarriages;
• Parents (one of them) have genetic translocations, chromosomal rearrangements, inversions and other genetic pathologies.
• More than 3 ineffective embryo transfers of adequate quality in women under 35 years of age.

To undergo the examination, a consultation with a geneticist is necessary, it is this specialist who will prescribe PGD. The price depends on the chosen method. Despite the cost, the feasibility of this diagnosis is difficult to dispute. Its reliability reaches 97%.

The use of preimplantation genetic diagnostics is possible exclusively within the framework of the IVF program, and at one time it became a real breakthrough in the field of assisted reproductive technologies. The ability to identify genetic disorders at the stage of pre-implantation development is a chance to significantly increase the effectiveness of infertility treatment and achieve the main goal - the birth of a healthy baby in the family.

Indications for PGD

Preimplantation genetic diagnosis is recommended in the case of diagnosed genetic disorders in one or both future parents. If a man and a woman are found to have abnormalities in the karyotype, PGD is one of the most important stages in the algorithm for preventing the birth of a child with pathology and the onset of pregnancy by a fetus with pathology. In this case, PGD involves the study of embryos for aneuploidy of chromosomes involved in translocations, as well as for the most common chromosomal abnormalities (Down, Patau, Edwards syndromes).

Fig. 1. Aneuploidies in an embryo on chromosomes 15, 20 and 21 in a 40-year-old patient using the NGS method.

PGD ​​is prescribed for IVF failures and recurrent miscarriage. Both with natural conception and within the framework of ART programs, the main number (75-80%) of pregnancy terminations occurs in the first trimester. The causes of miscarriage can be both genetic abnormalities of the embryo and multiple pregnancies. PGD ​​for miscarriage can help reduce the incidence of spontaneous abortion. In patients with a history of miscarriages, the rate of spontaneous abortions was reduced to 16.7% versus the expected 36.5%, in women over 35 - to 12% versus the expected 44.5%.

Fig. 2. Biopsy of trophectoderm cells in a 5 day embryo.

Preimplantation genetic diagnosis is also irreplaceable in the case of male factor infertility, when high rates of genetic abnormalities in sperm are detected. The study of chromosomes in spermatozoa obtained from men with oligo / astheno / teratozoospermia (OAT) showed an increased level of aneuploidy (wrong set of chromosomes) compared with men without abnormal sperm counts. In men with normal karyotype, the rate of sex chromosome aneuploidy in spermatozoa was observed with oligoasthenoteratozoospermia 4 times more often than with normal spermogram. The use of spermatozoa with a pathological set of chromosomes for fertilization leads to the formation of an embryo with a genetic pathology, and then, often, to fading and miscarriage, or the birth of a child with pathology.

Fig. 3. Genetic diagnosis in embryos by CF-PCR.

The reproductive specialist recommends PGD if a woman is over 35 years old, since, unfortunately, there are medical statistics that allow us to say that in the late reproductive period, the risk of having a child with genetic pathology, including Down's syndrome and serious diseases, malformations increases various organs and systems.

Indications for PGD

• cases of the birth of children with a history of hereditary and congenital pathology;
• diagnosed balanced chromosomal aberrations (translocations, etc.) in a pair;
• woman's age from 35 years;
• 2 or more unsuccessful IVF attempts in history;
• a history of freezing and miscarriage, as well as cases of cystic drift;
• a high percentage of sperm with a genetic pathology in a man;
• every family who wants to undergo PGD as part of an IVF program in order to be confident in the health of the unborn child and increase the chances of treatment success.

Fig. 4. The rate of pregnancy in the IVF program with and without genetic diagnosis.

PGD ​​capabilities

Preimplantation genetic diagnosis provides ample opportunities to identify genetic abnormalities in embryos and allows the transfer of a promising, viable embryo. Preimplantation diagnostics makes it possible to successfully implement the current trend of modern reproductive medicine - the selective transfer of one healthy embryo and the onset of pregnancy with one fetus, since multiple pregnancies have their own characteristics and obstetric risks.

Fig. 5. Analysis results obtained using the CGH and NGS method.

Thus, carrying out PGD reliably helps:

• increase the frequency of pregnancy;
• to increase the frequency of successful gestation;
• to reduce the frequency of occurrence of multiple pregnancies;
• reduce the risks of having a child with pathology.

How and when is PGD done?

Preimplantation genetic diagnostics includes 2 stages: obtaining cells from embryos using special laser equipment, which is safe for developing embryos; research of the obtained material in the genetic laboratory.

The collection of cells for PGD, as a rule, is carried out on the 5th day of development, at the blastocyst stage. It is during this period that the embryo already has a lot of cells, and, accordingly, DNA for analysis, which makes it possible to obtain more reliable and reliable diagnostic results.

In situations where there is a likelihood of passing on hereditary genetic pathologies to a child, a married couple who wants to have a baby is prescribed preimplantation genetic diagnosis (abbreviated as PGD, also known as PGD). With in vitro fertilization, this procedure becomes even more important, because the spouses will have to go a long way of treatment. PGD ​​in IVF can detect up to 150 chromosomal abnormalities even before the transfer of embryos into the uterine cavity. This minimizes the risk of having a baby with a genetic disease.

The study of the genes of both parents during IVF is very important, sometimes simply necessary.

General information about PGD

Preimplantation genetic diagnosis is a modern method that allows timely detection of chromosomal and gene abnormalities in the embryo, even before its introduction into the uterus. This procedure is usually carried out on the recommendation of a doctor, but a married couple themselves may express a desire as part of an in vitro fertilization cycle.

PGD ​​in IVF increases the efficiency of the protocol up to 70%.

The study of the chromosome set of a fertilized egg takes place in the laboratory. Since the study is carried out at the initial stage of embryo development, it is almost impossible to injure it. Fertilized eggs are examined simultaneously with the main treatment prescribed for the patient. To carry out PGD, a larger number of follicles are needed, therefore, the ovaries are stimulated with the help of hormone therapy more intensively.

The danger for the child is not all chromosomal abnormalities detected in parents, but their combinations with characteristic signs. It is these genes that are threatening factors affecting the possible development of pathologies in a baby.

Watch the recording of an interesting program about PGD:

Types of mutation signs

There are two types of mutation traits: dominant and recessive. When the first mutational species is transmitted to the baby, the risk of developing pathology increases by 50%. For example, if both parents "carry" a recessive trait, the manifestation of a genetic abnormality is possible when the baby receives "sick" genes of both men and women.

Whether a child with a pathology will be born also depends on the sex of the embryo. Since the 23rd pair of chromosomes in women is represented as XX, and in men - XY, if one of the female chromosomes is sick, the anomaly will not be transmitted to the baby. The second chromosome will prevent the transmission of the "diseased" gene. In this case, the child will also be the carrier of the "faulty" chromosome.

Unfortunately, men do not have such a defense mechanism in their bodies. Girls born from carriers of the "defective" chromosome will also be its owners, and boys will be born with a possible genetic pathology.

Difference between PGD and PGS in IVF

Preimplantation genetic diagnosis allows you to find out immediately which specific combination was inherited by the embryo. Thanks to PGD, expectant mothers and fathers will know if the baby will appear with a genetic abnormality, or will carry a chromosomal defect. All embryos for replanting are examined in the laboratory. After the research, the "cleanest" fertilized eggs are selected.

Some people confuse preimplantation genetic diagnosis with screening. In fact, these are completely different procedures. The task of PGD is to minimize the risk of having a baby with genetic problems. In PGS (pre-implantation genetic screening), the main task is to increase the chances of pregnancy. Genetic diagnostics examines embryos for genetic abnormalities, genetic screening, in fact, is the selection of the healthiest embryos for successful fertilization.

Another interesting video, now about screening (PGS):

PGD ​​in IVF is prescribed for:

1. Insurance against the transfer of embryos with "faulty" chromosomes.
2. Identification of the problem that served as a catalyst for the failure of the previous protocol.
3. Reducing the risk of having a baby with pathology.
4. Determination of the sex of the unborn baby in order to avoid genetic anomalies based on gender.
5. Identification of embryos with a predisposition to genetic diseases.
6. "Finding" the embryo most compatible with the HLA-system with other children of the family for donation during their treatment.
7. Reducing the risk of early termination of pregnancy.
8. Minimizing the risk of manifestations of hemolytic diseases in a child.
9. Choosing the "ideal" embryo for replanting, while excluding multiple pregnancies.

PGD ​​will allow to identify and exclude many pathologies dangerous for a child. For example, Gaucher's disease, Down syndrome, deafness, polycystic kidney disease. Total, preimplantation genetic diagnostics, capable of detecting more than 150 types of genetic diseases.

However, research is not always the key to the birth of a healthy child. Cases of false negative results have been noted, since some research methods reveal only a certain number of chromosomes, and the unaccounted ones turn out to be “faulty”.

Another option, when PGD is uninformative, is the mosaic development of anomalies. During diagnosis, the cell looks healthy, but mutates during development.

When to do PGD

Not every couple who decides to undergo IVF is offered to undergo pre-implantation genetic diagnostics. There are a number of indications for which this procedure is recommended.

Namely:

• The spouses have “defective” chromosomes, there are monogenic abnormalities, or a chromosomal rearrangement has been identified.
• Age couple (woman over 35, man over 40). The older the couple, the more likely it is to have a baby with gene abnormalities, even if the spouses do not have “faulty” chromosomes.
• Previous pregnancies ended in the death of newborns due to Rh-conflict.
• Examination of oocytes and sperm cells revealed the presence of defective genes and chromosomes.
• Unsatisfactory result. Revealed serious disorders such as azoospermia or oligozoospermia.
• In previous pregnancies did not occur.
• Pregnancy was terminated early in the development of the embryo.

The older the couple, the more necessary it is to do PGD.

Since the list of genetic diseases is quite impressive, IVF diagnostics are recommended for all patients over 35 years old... Age-related changes often threaten with unpleasant "surprises" during pregnancy, even if conception occurred naturally.

Accelerated aging of the female body and PGD

There are situations in which the female body “grows old” much faster in a biological sense. Certain factors contribute to the accelerated aging of the female body. Here is some of them:

• long-term use of potent drugs;
• unhealthy lifestyle in the past (smoking, alcoholism, drug addiction);
• chronic diseases;
• harmful working conditions;
• poor environmental situation.

PGD ​​is also necessary if:

• Certain stem cells need to be obtained to treat other children in the family.
• A man and a woman are close relatives.
• The couple received a share of the radiation exposure.

The cost of the IVF protocol with PGD is much higher than without the procedure, so the decision to carry out the diagnosis is made by the patient independently. It should be borne in mind that in only 20-40% of cases, embryo replanting ends in pregnancy (depending on the age of the patient).

PGD ​​allows not only to identify gene mutations in the embryo, but also to increase the likelihood of successful replanting (up to 70%, depending on age).

Embryos obtained with IVF from women over 40 are 50% more likely to have abnormal genes than from younger patients.

How PGD is done with IVF

It all starts with preparation. Preparation for diagnosis is a consultation and examination of spouses who have indications for PGD. The doctor will talk about the advantages and disadvantages of the procedure. Since the study will require a large number of mature eggs, the stimulation in the protocol will be more intense, which may cause hyperstimulation syndrome. After the examination, the couples proceed directly to the diagnosis itself.

The procedure is divided into 8 stages:

1. The eggs are removed and fertilized in a laboratory.
2. The cell develops within 3-5 days.
3. The most viable fertilized eggs are selected by laboratory technicians.
4. A biopsy is performed. Cells are removed from the embryo for analysis.
5. The blastomere is fixed.
6. Hybridization is in progress.
7. Bioinformatic analysis is being formed. The received data is decrypted.
8. The geneticist conducts PCA (medical genetic counseling of the patient).

PGD ​​does not in any way affect the development of organs and tissues of the unborn baby, therefore, the diagnosis does not affect the health of the embryo.

After PGD, the geneticist selects "clean" embryos - they will be suitable for transfer. Embryos with defective chromosomes are not implanted in the patient.

What are the PGD methods

Preimplantation genetic diagnosis is performed by 4 methods: FISH, CGH, PCR, NGS. Each of them has its own specifics, its pros and cons. Some methods are more expensive, others are cheaper. The more expensive the method is, the more accurate it is.

PGD ​​using FISH technology

In another way, it is called the molecular-cytogenetic method (English Fluorescent In Situ Hybridization). This diagnostic option is the most budgetary and is widely used throughout the post-Soviet space. However, the main disadvantage of this method is inaccuracy, because not all chromosomes are examined, but only a certain number of them.

Using the FISH method, a specialist in 5 hours determines the sequence of chromosomes in the embryo, the sex of the embryo, and will receive an answer to the question whether the unborn baby has common genetic abnormalities or not.

CGH method

Another name for the procedure is comparative genomic hybridization. This study takes much longer than the previous one. Its cost is also higher. However, the CGH method has many benefits.

Thanks to this research, you can:

• select the most viable embryos that are optimal for replanting to the patient;
• reduce the likelihood of a misdiagnosis, since a large number of stem cells are checked using this method;
• explore frozen germs to be used in.

Comparative genomic hybridization is carried out using a special chip. Scanning and processing of the results is carried out by a computer program, which minimizes the human factor.

PGD ​​PCR

Before examining embryos by PCR (polymerase chain reaction), the spouses must be diagnosed for the presence of gene abnormalities. This is necessary to eliminate errors in the diagnosis of a disease arising from cell mutations.

The tasks of the polymer chain reaction are to find flaws in the work of chromosomes and to identify monogenic pathologies. The method calculates the presence of antibodies incompatibility in spouses and the Rh factor of embryos.

If a donor egg is taken for the IVF procedure, PCR studies are not performed.

NGS method

The most modern diagnostic method is high-throughput sequencing. NGS is an acronym for Next Generation Sequencing and is literally translated as "next generation sequence." This study is the most expensive and most effective, allowing you to study all 23 pairs of chromosomes. The technology allows you to establish the initial nucleotide sequence of the desired DNA block or the whole human genome.

There are 5 variants of this method: pyrosequencing, sequencing on molecular clusters, technical ligase sequencing, ionic semiconductor sequencing and single-molecule sequencing. Each of them has its own characteristics.

How much does PGD cost

In vitro fertilization requires considerable expenses, including money. PGD ​​increases its cost significantly, since expensive equipment and materials are used. It is impossible to unequivocally answer the question about the cost of genetic diagnostics.

The price of the analysis depends on a number of factors. The broader and more precise the research, the more expensive it is.

The cost of PGD is influenced by:

1. Selected research method.
2. The number of embryos to be examined.
3. Conducting auxiliary tests.
4. Study of changes in the genetic structure of chromosomes.

The price of diagnostics is also influenced by the number of investigated anomalies. For example, in Moscow, the average cost of examining one embryo ranges from 20 to 30 thousand rubles. The price of a comprehensive study sometimes reaches 250 thousand rubles. On average, a comprehensive examination of both parents costs 150 thousand rubles. The price in the regions is slightly lower, but not significantly.

Write in the comments how you think this research is worth the money? If not, why not? Will you do PGD? Share this article on social networks with your friends, they may be interested to know about it. Don't forget to star rating. Thanks for visiting. Let your genes be the best and no anomalies!