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A couple who plan a pregnancy or is in its early stages, specialists can refer to a medical genetic examination.
Oksana Shishkanova obstetrician-gynecologist, Moscow
The birth of a child with a genetic pathology, according to medical statistics, in healthy people is only about 5%. This is not enough, but it's not very desirable to be in these percentages ...
To start a little about human genetics. In total, a person has 46 chromosomes (chromosomes are carriers of the genetic information of any living organism, they are contained in the nuclei of all cells). Each chromosome consists of a large number of genes, which determine the uniqueness of each biological species. Each gene is responsible for the formation of a certain trait in the human body. Thus, 23 future chromosomes the child will receive from the mother, 23 - from the pope. When the female egg is fertilized with the spermatozoon, the genetic material of the parents will connect, and the fertilized egg will contain a complete chromosome set (46 chromosomes). The future baby is not an exact copy of mom or dad, but a new and unique organism. Of course, the child will be more like one of the parents, but only to a certain extent. Nature also developed mechanisms for the natural selection of inferior embryos already at these early stages of pregnancy. According to statistics, 15% of fertilized eggs can not implant (implant) in the uterine mucosa, and menstruation in a woman comes on time. And about a possible pregnancy does not even become known.
Further after implantation, the embryo begins to grow, develops further, pregnancy progresses. In the presence of gross anomalies in the early stages of pregnancy, the inferior fetus ceases to exist, pregnancy is interrupted after a slight delay in another menstruation. Chromosomal abnormalities are the most common cause of spontaneous abortions in early life. So more than 90% of gross genetic breakdowns are eliminated.
Violations in the genome can be hereditary, that is, received by people from their parents or previous generations. But very often chromosomal abnormalities arise directly during the maturation of germ cells during one menstrual cycle of a woman and the period of spermatogenesis of a man. The effects of unfavorable factors (smoking, alcohol, viral infectious diseases, administration of antibiotics and a number of other drugs) can cause so-called mutations (irreversible changes in genetic material). The age of the spouses is also of great importance in the maturation of the sex cells. If the future parents are older than the optimal age for childbearing (for women under 35, for men the age range is less rigid - up to 40 years), these mechanisms of natural selection are weakened, so with an increase in the age of future parents, the risk of developmental abnormalities in the child is also higher.
Who needs a geneticist consultation?
Do all couples need to visit a geneticist before the pregnancy? If we talk with rational positions, probably not. In women with genotype disorders, spontaneous abortions and other reproductive disorders are 10 times more likely. Anomalies do not always have the character of gross violations. Thus, the compulsory approach to this specialist should be in the following situations:
- Birth in the families of spouses of children with genetic defects;
- stillbirths in the past (from the spouses themselves or their next of kin);
- spontaneous abortions in the past (here it is especially necessary to note the so-called anembrionia - absence of the actual embryo in the presence of the fetal egg);
- long-term infertility (with the exclusion of other common factors of absence of pregnancy);
- presence of genetic pathology in the spouses themselves;
- the age of a woman over 35 years, men over 40 years.
The diagnosis on ... palms?
Until recently, one of the informative methods of research in genetics was considered dermatoglyphics (the study of patterns and the structure of the palm of the palm). People with impaired reproductive function and genetic abnormalities identified certain features of the palmar pattern, but with the improvement of laboratory methods and the possibility of a more accurate analysis of genetic problems, this method is more of historical interest.
What research is carried out in genetic counseling?
First of all, a geneticist talks with future parents, makes a pedigree. This is the so-called genealogical study. A "genealogical tree" is made-who are parents, grandparents, close and distant relatives, what diseases they suffered, from which they died, whether there were reproductive disorders in them, etc. Then the data are analyzed and the degree of risk for the given couples and her future offspring of certain genetic anomalies. Pay attention to the presence of stillbirths, delayed intrauterine development, mental retardation, infertility.
Next, a cytogenetic study (blood test) of the spouses and counseling, the tasks of which are:
- Clarification of the chromosome set. Healthy people can be carriers of chromosome balanced rearrangements - naturally, not knowing about it. But if a child gets such a "not very high-grade" part of the chromosome, there may be a violation that will have its manifestations. And if both parents are carriers of similar sites? Then the risk of the disease will be much higher. That is why family marriages or alliances within closed communities are not welcome.
- Assessment of the risk for subsequent pregnancies in the past in a pair of spontaneous miscarriages or the birth of a child with developmental abnormalities.
- Clarification of the need for prenatal (prenatal) diagnosis in subsequent pregnancies. Such diagnostics include a number of studies that are conducted during pregnancy to clarify the condition of the fetus, including - allowing you to study the chromosome set of the fetus. There are recommendations for donor donation of eggs (in the course of this procedure, take an ovule of another woman, fertilize with the husband's sperm and transfer the resulting embryo to the patient's uterus) and donor sperm in the presence of a gross genetic pathology in one of the spouses.
How to reduce the risk of genetic pathology?
Recommendations not to drink alcohol, quit smoking and take vitamins several months before the onset of pregnancy are known to everyone, but, nevertheless, they have not lost their relevance. Especially important in this respect are the first 12 weeks of pregnancy - the time for the laying of all organs and systems. In addition, a pregnant woman should be excluded from taking various medications (antibiotics, sleeping pills and many others).
The future mum needs as much fresh air as possible; if possible, contact with viral infections should be avoided. While making a career in today's world, one should not forget about the biological age given to a woman for procreation. The age of 20-35 years is most favorable in this respect. The older age (especially for the first pregnancy) is an occasion for an in-depth genetic examination.
Not closely related marriages are not recommended. The closer the degree of kinship, the higher the risk of genetic abnormalities in offspring, infertility, the very arbitrary miscarriages and stillbirths.
Among the vitamins recommended for the future mother, especially it should be noted folic acid. Taking it three months before conception and during the first trimester of pregnancy significantly reduces the likelihood of fetal malformations of the nervous system and anterior abdominal wall. This is due to the fact that folic acid plays a huge role in the processes of doubling DNA and RNA nucleic acids, which are responsible for the storage and transfer of genetic information, as they are the main constituent element of genes and chromosomes. That is, folic acid provides cell division and tissue growth, and the neural tube is laid in the earliest stages of pregnancy.
Prenatal diagnosis before IVF
Last years the big role in treatment of barreness is played by programs of an extracorporeal fertilization - ECO. Fertilization of the ovum with the spermatozoon takes place outside the female body (in a "test tube"). Then the embryo (or even two or more) is transferred to the womb of the woman. In the future, the course of pregnancy does not differ from usual. In clinics that implement these methods of treatment, there are always genetic doctors advising spouses on infertility and the causes of non-pregnancy in each case. In the detection of genetic pathology, a pair may be offered:
donation of the egg (with genetic pathology of a woman);
donor sperm (with male infertility and genetic pathology of the husband);
prenatal diagnosis before transferring the embryo to the uterus (it is possible to conduct a study of the quality of human embryos obtained at the earliest stages of development, choose a healthy and transfer it to the uterus). This method is used not only in the presence of genetic abnormalities in spouses, but also in their absence. This program is usually resorted to couples of adulthood who have gone a long way in treating infertility.