TERMINOLOGY
Amniocentesis: The process of taking some fluid from the fluid in the sac surrounding the baby (amniotic fluid) with a thin needle for examination.
Amniotic Fluid: The fluid in the sac surrounding the baby (fetus). .
Aneuploidy: Having an abnormal number of chromosomes. It concerns all chromosomes, including sex chromosomes.
Trisomy: It is the condition of having an extra chromosome.
Monosomy: It is the condition of missing one chromosome.
DNA: It is the genetic material passed from parent to child. It is carried in chromosomes.
Embryo: It is the developmental process that starts with fertilization and includes the first 8 weeks of pregnancy.
Fetus: It is the baby in the development process that continues from the 8th week of pregnancy until birth.
Fluorescent In Situ Hybridization ( FISH): It is a laboratory technique used to screen for common chromosomal anomalies in cells taken by amniocentesis or chorionic villus biopsy. Since the cells do not need to be cultured beforehand, results are obtained quickly.
Gene: These are sections of DNA that contain information that controls the physical characteristics of the person and all body functions. The basic units of heredity are DNA. It is transferred from parent to child.
Genetic Counsellor: It is the expert in genetics
who provides information about genetic diseases and prenatal tests.
Genetic Disorders: Disorders that occur as a result of changes in genes and chromosomes.
Karyotype: It is the appearance of a person's chromosomes arranged from largest to smallest.
Chorionic Villus Sampling (CVS): It is the process of taking a small sample from the placenta for examination.
Chromosome: These are the structures located in each cell that carry the genes that determine the structure of the person.
br /> Cell: It is the smallest structural unit of the body.
'Microarray': It is a technique used to detect certain disorders or abnormalities in genes. It is a method that can detect very small genetic variations that cannot be detected in classical
genetic tests.
Mutation: It is called permanent genetic changes that can be passed from parent to child.
Placenta: It is the tissue that provides communication between the mother and her baby.
Diagnostic. Test: A test that looks for the disease or its cause.
Screening Test: A test that looks for a possible disease in those who have no signs or symptoms of the disease.
Carrier: It gives no signs of the disease. n, but the person who is likely to pass the disease to his child.
Ultrasound: An imaging method using sound waves to examine internal organs.
It is frequently used in pregnant women.
What is prenatal genetic examination?
These are tests that give parents information about the presence of some genetic disorders in their unborn babies.
What are genetic disorders?
They occur as a result of changes in a person's genes or chromosomes. The situation of having one missing or extra chromosome is called 'aneuploidy'. Hereditary diseases occur as a result of permanent changes in genes, called mutations
. In most cases, both parents must carry the same gene for the child to have the disease.
What are the basic prenatal tests?
There are two types of prenatal tests for genetic disorders:
1. Prenatal screening tests: It determines the risk of aneuploidy and some additional disorders in your baby.
2. Prenatal diagnostic tests: It definitely determines the presence of aneuploidy or a certain hereditary disease
in your baby. In diagnosis, fetal cells in the fluid taken by amniocentesis or placental cells taken by chorionic villus
biopsy are used.
Pregnant women should be offered both screening and diagnostic test options.
What is amniocentesis?
Amniocentesis is a prenatal diagnosis test. Most often 15-20. Even if it is done in a week, it is possible until birth. Some amniotic fluid (20 ml) is taken with a thin
needle. The procedure is performed under ultrasound observation. Depending on the laboratory
technique, results are given within a few days to a month. It carries a slight risk of miscarriage.
What is chorionic villus biopsy?
Chorionic villus biopsy is a prenatal diagnosis test. A tissue sample is taken from the placenta.
Advantage over amniocentesis:
Earlier application (10-13th week)
Faster results
In experienced hands, the risk of miscarriage is as low as amniocentesis.
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How are the cells examined in prenatal diagnostic tests?
Genetic counselors determine the appropriate method for your situation.
1. Karyotype — By observing a person's chromosomes arranged from largest to smallest, the chromosomes are identified as missing,
extra or missing. damaged chromosome is detected.
2. Fluorescent In Situ Hybridization (FISH) — Used to detect common aneuploidies (chromosome 13, 18, 21, X,
Y). of cells Results appear quickly (often 1-2 days) because no prior culturing is required. Positive results should be checked with karyotype.
3. Chromosome microarray analysis — It is a technique that searches for different types of chromosome problems that are too small to be seen by karyotyping
in the entire chromosome set. Results are available in 7 days.
4. DNA test — Examination can be performed for known genes. For example, do parents carrying Mediterranean anemia have the same disease in their fetus?
What do prenatal diagnosis test results mean?
Most of the time, the result is 'negative', that is, normal. A negative result cannot exclude the possibility
of a genetic defect in the baby. It just indicates that the genetic condition being examined is not present. If the result is 'positive', it means the existence of the situation examined
. Your doctor and genetic counselor explain the results to you and offer you options; Thus, it helps you make a decision. The specialist enlightens you about the relevant situation; helps you understand the situation by explaining
postnatal life expectancy, quality of life, treatment options, if any, and the requirements for the care of the child. It is useful to get help from support groups, psychological counselors,
social workers. Sometimes further examination may be required regarding the situation.
Should I have a prenatal genetic test?
The decision whether to have the tests or not is entirely yours. Your beliefs and values play an important role in making this
decision. Remember that certain tests are performed at certain weeks of pregnancy. Tests that can be performed earlier give parents time to decide. Moving early means less risk for both mother
and fetus.
Should I have a prenatal genetic test?
It is wise to consider in advance how you will act if the test result is 'positive'. Do some couples
have a genetic disease in their babies? He wants to learn. It becomes easier to plan and organize everything in advance. In some cases, they may prefer to terminate the pregnancy. Some couples do not want to know anything before
birth. That's why he doesn't get tested. There is no right or wrong.
The decision is yours.
Screening test? Diagnostic test?
Diagnostic tests:
Chromosome number and structure disorders It detects most of them.
There are diagnostic tests for most hereditary disorders.
Its main disadvantage is the slight risk of miscarriage.
The genetic counselor can recommend special tests by taking family history and interprets the results.
Conclusion
Prenatal genetic examinations are tests that give parents information about the presence of some genetic disorders in their unborn babies.
There are two types of prenatal tests for genetic disorders:
Prenatal screening tests: It determines the risk of aneuploidy and some additional disorders in your baby.
Prenatal diagnostic tests: It definitely determines the presence of aneuploidy or a certain hereditary disease in your baby
. In diagnosis, fetal cells in the fluid taken by amniocentesis or
placental cells taken by chorionic villus biopsy are used.
Pregnant women should be offered both screening and diagnostic test options. In prenatal diagnostic tests, genetic counselors determine the appropriate method for your
situation. Most of the time, the result is 'negative', meaning
normal. If the result is 'positive', it means the presence of the examined condition. Whether to get tested or not, in the end there is no 'right' or 'wrong' path to follow. The decision is entirely yours.
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