Genetic diagnosis procedures are procedures performed by obtaining the cells of the baby in the womb. For this purpose, a needle is used to enter the baby's partner (Placenta), the fluid in which it floats (Amniotic fluid) or the umbilical cord (cordocentesis) under ultrasonography and a sample containing the cells is taken. Amniocentesis at 16-22 weeks of pregnancy. Chorionic villus sampling was performed between weeks 10-14 of pregnancy. cordocentesis is performed after the 22nd week of pregnancy. Generally, the main reason for these procedures is to detect a high risk of chromosomal disorder in the baby or to detect a possible genetic disease. The most common reasons are the high risk of trisomy 18 or 21 in screening tests (double, triple test, quadruple test); It is the presence of Down syndrome or another chromosomal disorder in the family or the detection of findings suggestive of chromosomal disorder in detailed ultrasonography.
How is the chromosome analysis (genetic diagnosis) of the baby in the womb performed?
Genetic disease determination (karyotype analysis) is performed by culturing cells from the blood, amniotic fluid and placental tissue, examining the chromosome regions of the baby from these cells and performing chromosome counting. The most commonly known chromosomal disorder is Down Syndrome. Frequently, by chromosome analysis, the baby's chromosome structure is determined with 99.7% reliability and genetic diagnosis is made within 15-21 days. In cases where rapid results are required, genetic diagnosis can be achieved in a few days by looking at the results of certain chromosomes (most commonly 13, 18, 21, X and Y chromosomes) using the FISH or QF-PCR method. The probability that the FISH or QF-PCR method will be normal and the full chromosome analysis will not be normal is very low. Very rarely, a second attempt is needed in cases where there is no growth in the cell culture.
Many different genetic tests (conventional cytogenetics, molecular methods) can be performed depending on the result desired to be obtained from the cells taken. Markers for metabolic diseases, hereditary anemias (sickle cell anemia, Mediterranean anemia), fetal blood group, and intrauterine infections can be investigated. The perinatology specialist who evaluates you and the medical genetics specialist whose knowledge is consulted will decide which tests should be performed on the sample taken.
Amniocentesis v Can chorionic villus sampling also be performed in twin pregnancies?
Both procedures can also be applied in multiple pregnancies (twin pregnancy, triplet pregnancy).
What should I do before my genetic diagnosis appointment?
There is no need for any special preparation before these procedures. However, be sure of your blood type before each of the 3 procedures. In couples with blood incompatibility (Rh), it is recommended to administer Anti-D immunoglobulin (Rhogam) (blood incompatibility injection) to the expectant mother within 72 hours after the intervention.
What happens to my daily life after amniocentesis and chorionic villus sampling? When can I return?
After the procedure, I can return to daily life after approximately 2-3 days of rest. There is no harm in the pregnant woman taking a bath or shower the day after the procedure.
Are the tests that investigate the free DNA of the fetus in the blood sample taken from the mother equivalent to genetic diagnosis tests? strong>
No. These tests are actually screening tests, their scope is limited, their most important advantage is that they reduce unnecessary genetic diagnosis procedures due to false positivity of the screening test. Low-risk results are meaningful, especially for Down syndrome. If the results are reported as high risk, a genetic diagnosis method such as amniocentesis or chorionic villus sampling should be used. New data are needed to use these tests as first-line screening tests. You can get information from a perinatology specialist for more detailed information on this subject.
For more detailed information, you can get information from a perinatology specialist.
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