Cytogenetics is the science that studies chromosomes by number and structure. In cytogenetic analysis, chromosomes are obtained from cells that can divide, such as blood, skin biopsy, amniotic cells, and low material. In addition, chromosomes can be obtained directly from some tissues such as bone marrow, chorionic villi, and testis.
Prenatal Diagnosis Methods
During the follow-up of the obstetrician, genetic tests can be performed by interventional methods when necessary. These are called prenatal diagnostic tests.
The process of transabdominal removal of amniotic fluid from the farthest place to the baby’s head under the guidance of ultrasound is called amniocentesis. The amniotic fluid consists of cells poured from the baby’s skin, respiratory system, digestive system, and excretory system, and mostly baby urine. Amniotic fluid can be taken up to 10-20 cc ideally between 15-18 weeks of gestation. The test result is given within 2-3 weeks.
Chorionic Villus biopsy
It is the procedure of taking a biopsy from the chorionic villi by trans-cervical or trans-abdominal route, ideally at 11-13 weeks of gestation, from the farthest place to the baby’s head under ultrasound guidance. The test result is taken within 2-3 weeks.
It is the procedure of taking 2 ccs of fetal blood sample directly from the umbilical cord into a heparinized tube under the guidance of ultrasonography in pregnant women who are at 20 and/or older gestational weeks. The test result is taken within 5-10 days.
For a detailed and accurate analysis of the unbalanced chromosomal material in the entire genome, more specifically, when there are fine deviations from the balanced genome, the CGH (Comparative Genomic Hybridization) technique is required and it is possible to investigate chromosomal anomalies in more detail, especially with the array-based CGH technique, which cannot be confirmed by conventional methods.
During pregnancy, if your baby’s chromosome analysis resulted normally even though your doctor saw an anomaly in ultrasonography examination, or if normal chromosome structure was found in chromosome analysis made from abortion material, molecular karyotyping, which is a much more sensitive technique, may be recommended as further examination. The test result can be obtained within 10-20 days.
Postnatal Diagnostic Methods
Postnatal Diagnosis is a chromosomal examination made from various tissues such as peripheral blood or abortion material, skin, and/or gonad in the newborn, child, or adult after birth.
Chromosome analysis can be performed from 2-5 cc blood taken from the arm into a heparinized tube, regardless of hunger/satiety. The test result can be obtained within 10-15 days.
In abortions occurring for any reason, it is possible to perform chromosome analysis of the fetus by studying the placenta. The test result can be obtained within 2-3 weeks.
Molecular Cytogenetics Laboratory
The fluorescent in situ hybridization (FISH) technique is a molecular cytogenetic method based on the hybridization of the patient’s DNA with normal DNA particles (probes) labeled with fluorescent dyes in its environment without disrupting the chromosome structure. The FISH method can be used to detect numerical or structural anomalies of prenatal and postnatal chromosomes, as well as in cancer genetics and Preimplantation Genetic Diagnosis (PGD). The test result can be obtained within 5-7 days.