Genetic testing before pregnancy. How are genetic studies carried out? What you need to say about genetics when planning a pregnancy

A couple planning to conceive a child can significantly reduce the risk of having a baby with pathologies. To do this, it is necessary in advance, even before pregnancy, to undergo a complete medical examination in order to identify the presence of health problems in each of the future parents. Sometimes it’s not enough to take tests and visit specialists from the standard list. An analysis for genetics when planning a pregnancy is rarely prescribed, but if the gynecologist considered that it was necessary, it must be passed!

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Who is at risk

A child with a genetic pathology can appear even in perfectly healthy parents. However, if mom or dad has a predisposition to conceive such a baby, it can be detected with almost one hundred percent probability using a set of genetic studies.

The list of signs on the basis of which future parents are determined to be at risk:

mom, dad or any of their close relatives were previously diagnosed with genetic diseases, for example, schizophrenia, Alzheimer's disease, Down's syndrome and others;
previously born children (not necessarily common) have been identified genetic abnormalities;
the couple's attempts to conceive a child for more than a year remain unsuccessful;
in the history of the mother there are already cases, or the birth of a dead baby;
the age of the expectant mother is less than 18 or more than 35 years old, and the father is more than 40 years old;
the spouses themselves are related to each other by blood relatives;
the work of one or both spouses involves contact with harmful substances that can affect the genetic characteristics of a person;
a woman has to take medications that can harm the fetus or significantly affect its development.

If there is even a suspicion that one of these threatening factors is present in the life of a couple planning to conceive, genetics is a must.

Analysis of genetic incompatibility

It is especially important to undergo this genetic study for couples who have been unsuccessfully trying to conceive a child for a long time, as well as for women with a disappointing diagnosis of infertility.

This analysis involves the study of HLA (human leukocyte antigen) of each spouse. The fact is that with their strong similarity, carrying a pregnancy becomes simply impossible. The woman's body simply does not produce special antibodies designed to protect the placenta and fetus, which in this case are perceived as something alien, and are rejected.

For research, blood from a vein will also be taken from the spouses, but the degree of similarity of their chromosomes is already being studied. The more they differ, the more likely it is that a woman will be able to conceive and bear a healthy baby. Total genetic incompatibility is diagnosed extremely rarely. The result will be available in a couple of weeks.

DNA diagnosis of the presence of certain diseases

A woman or a man may have previously given birth to children with diseases such as phenylketonuria or cystic acidosis. In this case, the list of genetic tests when planning a pregnancy also includes DNA studies that identify the risk of such disorders in the next child.

Interpretation of results

With a complete examination for genetics, it is possible to predict in advance the presence of more than 60 types of monogenic genetic abnormalities in an unborn child, as well as 4 multifactorial pathologies. Analyzes allow you to find out if any of the spouses is a carrier of mutant genes, which often become the cause of the birth of a sick baby.

With the help of genetic tests, it is also possible to identify the risk of complications during gestation, which makes it possible to take up their prevention in time.

The doctor measures the degree of risk in percent. An indicator of more than 20% indicates a high probability of having a child with genetic disorders. If it is less than 10%, then most likely there will be no problems with genetics. The medium-risk range is between 10 and 20%. If the risks are assessed as very high, then the specialist may advise the spouses to refrain from conceiving a child or recommend one of the IVF donor programs. With an average probability, a woman will have to take repeated tests already during pregnancy.

Whatever the results of the genetic examination, they are not the final verdict. However, a timely analysis often helps not only to learn about the risks of having a sick child, but also to do everything possible to reduce them.

During genetic analysis, geneticists study the genes that are responsible for the transmission of hereditary data from parents to children. They calculate the probable result of conception, determine the dominant signs of the fetus, as well as possible diseases with malformations.

The ideal option is considered to be an appeal to genetics at the stage of pregnancy planning.

What does genetic analysis show during pregnancy?

An analysis for genetics during pregnancy is carried out so that you can find out information:

whether future parents are genetically compatible;
the risk of hereditary predisposition of the baby to certain diseases;
whether the mother and child have infectious agents;
a genetic passport of a person, where a combined DNA analysis is located, reflecting information about the uniqueness of a particular person.

The above information will help prevent violations with the health of the baby.

Special attention should be paid to genetic testing during missed pregnancy. Sometimes it is because of congenital thrombophilia that multiple miscarriages occur. Repeated cases of a non-developing fetal egg in a woman are a reason to send material for determining the karyotype with the chromosome set of the embryo. A specialist can examine the content of IL-4 in a pregnant woman: when the fetus freezes, the level of cytokines is reduced.

Why and for how long to take the analysis

After the occurrence of a chromosomal mutation, the structure of the DNA molecule changes, a fetus with severe anomalies is formed. To prevent pathology, doctors recommend planning a pregnancy with genetic tests that demonstrate almost 100% accuracy in confirming fetal developmental disorders.

To assess intrauterine development, specialists conduct ultrasound diagnostics and a biochemical test. They do not pose any threat to the health or life of the baby. The first ultrasound of a pregnant woman takes place at a period of 10-14 weeks, the second - at 20-24 weeks. The doctor detects even minor defects in the crumbs. At 10-13 and 16-20 weeks, expectant mothers pass a genetic deuce: this is the name of the blood test for hCG and PAPP-A.

If, after applying the above methods, a specialist reveals a developmental pathology, invasive tests are prescribed.

They are performed during the following periods of gestation:

Chorionic biopsy: for a period of 10-12 weeks.
Amniocentesis: 15-18 weeks.
Placentocentesis: 16-20 weeks.
Cordocentesis: at the end of 18 weeks.

Indications for analysis

A genetic test is mandatory if the pregnant woman is included in the risk group:

the expectant mother exceeds 35 years of age;
the expectant mother has already had children with congenital anomalies or deviations;
in a previous pregnancy, a woman suffered dangerous infections;
the presence of a long time of alcohol or drug addiction before the onset of fertilization;
the presence of cases of spontaneous miscarriage or stillbirth.

High risk group

The expectant mother is under 18 or over 35 years of age.
The presence of diseases of a hereditary nature.
Women who gave birth to a child with developmental anomalies.
Having in the past or present time any kind of addiction - alcohol, drugs, tobacco.
Couples suffering from dangerous infections - HIV, hepatitis, pregnant women who have had rubella, chickenpox, herpes in the initial stages of gestation.
An expectant mother who took medications that are undesirable for use during childbearing.
Received a dose of radiation at the beginning of gestation due to the passage of fluorography or x-ray examination.
Women engaged in extreme sports in their youth.
Expectant mothers who have taken a high dose of UV radiation.

Sometimes a woman does not know about the conception that has occurred, being exposed to adverse factors. Therefore, the risk of falling into the risk group appears in many pregnant women.

Preparatory measures

How to prepare? Before donating blood, try not to eat in the morning or take the test after 5 hours after eating.

To prepare for an abdominal ultrasound, drink half a liter of plain water 30 minutes before the examination to fill your bladder. Follow the diet for 1-2 days. Refrain from eating foods that cause fermentation: cabbage, grapes, black bread, carbonated drinks. If you need to have a vaginal examination, take a shower beforehand and empty your bladder before the procedure.

How genetic analysis is done - research methods

A geneticist studies in detail the pedigree of future parents, assesses the risk of hereditary diseases. The specialist takes into account the professional sphere, environmental conditions, the impact of drugs taken shortly before the visit to the doctor.

The doctor conducts a study of the karyotype, which is necessary for a future mother with a burdened history. It makes it possible to analyze the qualitative and quantitative chromosomal composition of a woman. If the parents are close blood relatives or there has been a miscarriage, HLA typing should be performed.

The geneticist conducts non-invasive methods for diagnosing congenital anomalies in the development of the fetus - ultrasound and tests for biochemical markers.

The latter include:

determination of the content of hCG;
blood test for PAPP-A.

Another test was patented by an American company. At week 9, the expectant mother donates venous blood, which contains hereditary information - the DNA of the child. Specialists count the number of chromosomes, and in the presence of pathology, a number of syndromes are detected - Down, Edwards, Patau, Turner, Angelman.

If non-invasive examinations reveal abnormalities, the specialist conducts an invasive examination. With their help, material is taken, the karyotype of the baby is determined with high accuracy to exclude hereditary pathology - Down syndrome, Edward.

These methods include:

Chorionic biopsy. The doctor punctures the anterior abdominal wall, and then takes the cells of the emerging placenta.
Amniocentesis. They take a puncture of the amniotic fluid, evaluate its color, transparency, cellular and biochemical composition, volume, and hormone levels. The procedure is considered the safest of the invasive diagnostic methods, but it takes a lot of time to obtain a conclusion. The examination reveals anomalies that appeared during pregnancy, assesses the level of fetal development.
Cordocentesis. The study consists in conducting a puncture of the umbilical cord with a blood sample from the child. The method is accurate, and the results are known in a few days.
Placentocentesis. The analysis of placental cells is carried out.

As a result of the tests, the specialist makes a genetic prognosis for the parents. On its basis, it is possible to predict the likelihood of the appearance of congenital pathologies in a baby, hereditary diseases. The doctor develops recommendations to help plan a normal pregnancy, and if conception has already occurred, determines whether it is worth keeping it.

Evaluation of results

The tests are deciphered by a specialist geneticist, who, if a pathology is detected, will talk about the risks of complications, methods for their solution.

In the 1st trimester, studies are carried out to diagnose Down and Edwards syndrome in the fetus. On ultrasound, the doctor examines the thickness of the collar space. When TSV exceeds 3 mm, there is a huge threat of pathology.

The determination of the level of hCG and the beta subunit of hCG is also used. In the normal course of early pregnancy, every 3 days by week 4, the hormone content rises until week 9, and then falls. If the amount of the hCG beta subunit is higher than normal, there is probably an increased risk of developing Down syndrome, if lower - Edwards syndrome.

During gestation, PAPP-A values should increase. If the indicator is below normal, there is a risk of Down syndrome or Edwards syndrome. Experts do not consider an increase in PAPP-A to be a violation: with such a content, the likelihood of a baby’s diseases is no greater than with a normal amount.

In order for the risk calculation to be correct, do research in the laboratory where the risk is calculated. The program is built on special parameters, individual for a particular laboratory, and draws up a conclusion in a fractional form. For example, 1:250 means that out of 250 pregnant women with identical indicators, 1 baby is born with Down syndrome, and the remaining 249 are healthy. If you get a positive result, you will need to rescreen in the 2nd trimester.

Is genetic analysis necessary during pregnancy - pros and cons

There are several points of view on whether or not to do a genetic test. Many gynecologists argue that research is necessary when the expectant mother is at risk. To undergo a genetic study or not, it is up to the pregnant woman to decide.

The prices of tests are quite high, so many parents try to save money on them. However, for those who are more important to learn about the development of the child, the rates are not so important. With the formation of a congenital pathology or the inheritance of certain diseases, the couple will be ready for the birth of a baby with abnormalities or decide to have an abortion.

Many impressionable women experience severe stress during screening, which is undesirable during pregnancy, especially at the beginning of pregnancy.

Doctor's opinion about genetic tests:

Conclusion

Expecting the birth of a baby, all parents dream that he will be healthy and strong. However, sometimes it happens that a child has gene or chromosomal mutations that disrupt the normal development of the crumbs.

Gross congenital pathologies and hereditary diseases are not amenable to treatment, and in many cases an interruption must be made. To protect yourself from this, it is recommended to visit a geneticist in advance and conduct the necessary research.

A bit of a glimpse into the future allows genetic analysis. Whether this examination is necessary when planning a pregnancy, whether it is worth fearing and what the tests will show - this is discussed in detail in our material.

genetic lottery

Every year, scientists and the public learn more and more about human genetics. This allows you to avoid many troubles, to prevent them. But still genetics remains one of the most mysterious sciences.

Genetics is the science of the patterns of heredity and variation. For three decades in our country (since the mid-30s of the 20th century), scientists involved in this area of science have been persecuted, up to a complete ban on genetic research. Finally, the taboo on genetics was lifted in the USSR only in 1965.

So, practice shows that a child with genetic abnormalities can be born to absolutely healthy parents, regardless of their lifestyle and place of life, habits and age. At the same time, previous and subsequent children in such a family may be without any features.

According to Russian statistics, about 5% of children in our country are born with genetic abnormalities of varying severity and manifestations. Please note that their presence does not always mean a catastrophe for the child and his loved ones.

The main purpose of genetic analysis when planning a pregnancy is to identify possible genetic abnormalities that a child may inherit, and, therefore, increase the chances of taking measures that contribute to the birth of a healthy baby.

At-risk groups

Certain genetic abnormalities can also appear in a child born from healthy parents. But there are people who fall into an increased risk group:

if the expectant mother is over 35 years old, and the future father is over 40 years old;
if the potential parents are closely related. It must be remembered that geneticists and cousins are considered close, and therefore dangerous in terms of genetic deviations in descendants from such marriages. Third cousin relationship, according to geneticists, no longer poses a danger;
if a child with genetic defects has already been born in the family;
if at least one of the parents has an established genetic pathology or suspicion of it;
if the girl previously had or the birth of a dead child;
if one of the parents was exposed to harmful factors (for example, radiation or chemicals);
if the time of conception coincided with taking medications that are incompatible with pregnancy.

Even if none of the future parents fall into the listed risk groups, doctors advise undergoing genetic testing. You may or may not know the dangerous facts that may lead to genetic pathologies in the unborn child, or deviations can only be detected during appropriate examinations and do not manifest themselves in any way.

What is included in the genetic analysis when planning a pregnancy

At the first stage, the specialist will analyze the pedigree of future parents and collect the most complete information about their lifestyle, the harmful factors they encountered, etc. But since this analysis is carried out on the basis of the words of the couple themselves, who may not be aware of, for example, hereditary diseases, this is not enough for a conclusion.

Try to provide the doctor with the most complete and frank information on the questions that he will ask you. The slight insanity of your great aunt can only seem sweet and funny to you, but the geneticist will appreciate it from a completely different position.

The second stage of genetic analysis may include blood tests for biochemistry, examinations by specialized specialists (for example, a neurologist, therapist,).

The third stage is special chromosomal analyzes of each of the future parents.

Genetic tests during pregnancy

Regardless of whether future parents consulted a geneticist before conception or not, the girl goes through a genetic test.

Expert opinion:

Belokurova Maria,obstetrician-gynecologist, reproductologist, ultrasound diagnostician, Ph.D. Center for Reproductive Health "SM-Clinic" in per. Raskovoy, 14:“The term “genetic analysis” refers to several types of analyzes. Firstly, this is the determination of the karyotype (that is, the structure and number of chromosomes) of future parents. This analysis is recommended to take before planning pregnancy. Secondly, this is genetic screening, which is performed on already pregnant girls. Currently, all expectant mothers, regardless of age and lifestyle, undergo genetic screening of the first trimester (the so-called “double test”) for a period of 11-13 weeks, which includes ultrasound and determination of hCG and PAPP protein levels in the blood. Based on the results of this screening, a risk group of patients with possible genetic abnormalities of the fetus, such as Down syndrome and others, is identified. If a high risk is identified, a consultation with a geneticist is recommended to resolve the issue of the need, timing and methods of additional examination (analysis of amniotic fluid, chorionic villi, etc.) for a more accurate diagnosis of the problem. For a period of 16-18 weeks, a second genetic screening (“triple test”) is performed, which also includes ultrasound and a blood test for alpha-fetoprotein, hCG and estriol. At the 20-21st week of pregnancy, the III obligatory ultrasound of the fetus is performed, which excludes fetal malformations, since by this time all the organs of the unborn baby are formed and then only their growth occurs. In addition, there is currently the newest method of genetic analysis of the fetus, when blood cells of the fetus are isolated from the blood of the expectant mother and its karyotype is determined from them.

What do geneticists say?

Genetics is not mathematics. Even the most qualified specialist in this field, who has the most modern and accurate equipment for analysis, will never make 100% predictions, whether positive or negative. The fact is that, firstly, several thousand inherited diseases have already been discovered, and hundreds more are established every year, and, secondly, it is impossible to predict for sure how exactly the genes of the parents will be combined in a child. Therefore, when voicing the results of examinations, geneticists use the wording "low risk", "medium risk" and "high risk".

Low risk is a very good indicator. Don't ask the geneticist for a more accurate prediction.

In the conclusion of the geneticist, you will find the percentage of genetic risks. How to decrypt them:

Up to 10% - low risk. This is the best possible option.
10-20% - medium risk. These data will require careful medical monitoring throughout pregnancy.
Over 20% is a high risk.

Genetic examination when planning pregnancy plays a very important role, as it makes it possible to minimize the likelihood of having a baby with any pathologies. Unfortunately, most of the embryos die in the early stages precisely because of various anomalies and genetic failures. What is this examination, you will find out below.

For some couples, a genetic consultation in preparation for conception is mandatory:

if any of the parents in the family had genetic diseases,
Husband and wife are related to each other
previous pregnancies ended in stillbirth, miscarriage, missed abortion,
the couple has children with developmental disabilities,
age: women under 16 or over 35 years old, men over 40 years old,
at least one of the parents has been in contact with radiation, chemicals that can adversely affect the conception and development of the baby,
one of the spouses took drugs that are incompatible with pregnancy,
the couple fails to conceive a baby for 12 months or more.

Important: one of the main causes of miscarriage is the genetic incompatibility of husband and wife. This happens if the HLA (this is a human leukocyte antigen) of a man largely coincides with the HLA of a woman. As a result of this combination, the woman's body perceives the embryo as a foreign body, rejecting it.

The main task of a genetic study when planning a pregnancy for the compatibility of spouses is to identify discrepancies in the chromosomes of future parents. And the more inconsistencies, the higher the chance to endure and give birth to a healthy baby.

What is a pregnancy planning consultation?

Even a healthy person can be a carrier of damaged genes.

At the appointment, the geneticist will conduct a thorough survey of the couple about past illnesses, lifestyle, chronic ailments, as well as the health of the husband's and wife's relatives. All this information is needed by a specialist in order to schedule an examination for future parents. As a result of the analyzes, the geneticist individually draws up a genetic prognosis for the development of the child, and also determines the risk of developing diseases and gives recommendations on planning pregnancy.

If a couple is in a risk group, they must undergo cytological examination(in order to determine the quantity and quality of chromosomes), a man must pass (to exclude possible pathologies in the sperm), you also need to pass HLA - typing(to determine the compatibility of spouses).

There are 3 levels of risk, which are determined by the results of a genetic study:

low (up to 10%) - the couple will have a healthy baby,
medium (10-20%) - the possibility of some pathologies of fetal development is not excluded. Therefore, a woman will need to be observed during childbearing,
high - in this case, it is better to refrain from pregnancy, since there is a high probability of having a baby with serious pathologies (but you can use it).

What is the essence of cytogenetic analysis?

Cytogenetic analysis is a blood test of spouses, which makes it possible to:

Analyze the chromosome set of a man and a woman.

Even an absolutely healthy person can be a carrier of some chromosomal rearrangements and not be aware of it. This will not affect his health in any way, but the development of the child may not be displayed in the best way.

Assess the degree of risk for future pregnancies, taking into account past complications (miscarriages, missed pregnancies, birth of children with developmental anomalies).
Assign and explain the need for prenatal diagnosis in future pregnancies.

This type of diagnosis involves conducting tests in the process of bearing a child. It allows you to clarify the condition of the fetus, as well as determine its chromosome set.

Interesting: Chromosomes can only be seen under a microscope at certain stages of cell division. Therefore, in order to study the chromosome set of future parents, they take blood from which lymphocytes are isolated. Next, the cells are stimulated to start dividing and, at a certain stage, they are treated with a special solution that stops division precisely at the stage when the chromosomes are visible.

Then a special dye is used, thanks to which each individual chromosome acquires a specific shape. A geneticist studies chromosomes 11-13 in order to identify changes in the karyotype (set of chromosomes).

Methods of genetic examination

After the woman is registered, the gynecologist conducts a thorough survey and examines the patient's outpatient card in order to have an idea of the possible risks to the development of the fetus.

Sometimes already at such an early date, a pregnant woman is referred for a consultation with a geneticist. The period at which a pregnant woman needs to be seen by genetics depends on the indications:

All methods of genetic examination are divided into 2 groups: invasive and non-invasive.

Non-invasive methods

The first ultrasound examination is carried out for a period of 11-12 weeks. During this period, it is already possible to identify some malformations of the fetus. This may be indicated by a thickening of the collar zone of the fetus (often this is a sign of Down's syndrome).

Women with similar ultrasound results are referred for additional studies that make it possible to obtain a sample of cells from the placenta in order to reliably determine the chromosome set of the fetus.

The second ultrasound - the examination is carried out for a period of 20-22 weeks. During this period, deviations in the development of the face, arms and legs, as well as the internal systems and organs of the fetus, can be detected.

Ultrasound for a period of 30-32 weeks allows you to assess the state of the circulatory system, as well as determine the delay in fetal development.

This is how amniocentesis is done.

Biochemical blood test (screening)

Embryonic tissues of the fetus produce special proteins: protein (PAPP), human chorionic gonadotropin (hCG), alpha-fetoprotein (AFP). By changes in the concentration of these substances in the blood of a pregnant woman, various pathologies of fetal development can be determined.

Such studies are carried out within a certain period of time. The level of PAPP and hCG is determined for a period of 10-13 weeks. AFP level - for a period of 16-20 weeks. If the results of the study are outside the normal range, the woman is referred to a geneticist.

Invasive diagnostic methods

These studies are carried out exclusively for compelling medical reasons, as they can harm the health of a woman and a child. Invasive diagnostics involves taking material (cord blood, placental cells, amniotic fluid) from the uterus to determine the karyotype of the fetus and exclude or confirm diagnoses with developmental delay.

These studies are carried out in a hospital under ultrasound control. After the tests, the woman is under the supervision of specialists for another 3 hours. Sometimes, certain medications are prescribed to prevent complications in a pregnant woman. Diagnostic methods have been developed to identify 300 out of 5,000 existing hereditary diseases.

TO invasive research includes:

Chorionic biopsy

This is a collection of cells from the placenta. It is carried out for a period of 9-12 weeks. The material is taken through the abdominal wall of the woman. The results are obtained 3-4 days after the study. The risk of miscarriage after a chorionic biopsy is about 2%. This method has the following advantages: early term, quick result, which allows to identify serious pathologies of fetal development and terminate the pregnancy in the early stages.

Amniocentesis

This is the sampling of amniotic fluid for a period of 16-24 weeks. This invasive method is the safest, as the risk of miscarriage after amniocentesis is only 1%. But there are some drawbacks: the cells obtained after sampling are not enough for analysis. They need to breed, and for this you need to spend a lot of time - about 2-6 weeks.

Cordocentesis

Cord blood analysis is a highly informative method that takes about 5 days to obtain results. It is carried out for a period of 22-25 weeks.

Placentocentesis

This analysis involves the collection of placental cells for research. It is carried out for a period of 12-22 weeks. The risk of complications after analysis is 3-4%.

All of the above methods of examination are carried out with anesthesia and under strict ultrasound control.

The genotype of father and mother when planning pregnancy

In genetics, there are two main concepts: phenotype and genotype. A genotype is a set of genes. Phenotype - external manifestations of a particular trait, which depends on both the genotype and external factors.

Ultrasound at 9-11 weeks allows you to identify abnormalities in the development of the fetus

A person has about 35,000 genes that are unique, like fingerprints. The study of the genotype makes it possible to find out the genetic characteristics of a person, his heredity, compatibility with another person, predisposition to many diseases.

People with the same blood type can have a completely different set of genes.

Interestingly, there are some amazing patterns:

if dad and mom have the first blood group, the baby will have only the first group,
if mom or dad has the first group, the child cannot have the fourth blood group,
if at least one of the parents has the fourth blood type, the baby cannot have the second.

Prevention of genetic abnormalities of the fetus

In recent years, when planning pregnancy, periconceptual prophylaxis has been widely practiced, which makes it possible to significantly reduce the likelihood of having a baby with any congenital anomalies. Periconception prophylaxis suggests:

Examination of future parents before conception, which makes it possible to identify and treat various diseases. Infections, hormonal disruptions, disruptions in the endocrine system can adversely affect the conception and formation of organs and systems of the fetus.
Taking multivitamin complexes 2-3 months before the intended conception. Preparations must contain: B vitamins, folic acid, ascorbic acid, vitamin A.
Genetic examination when planning pregnancy allows you to identify various pathologies of fetal development in the early stages.

4. Closely related marriages are highly undesirable: the closer the relationship between husband and wife, the higher the risk of having a child with serious developmental anomalies.