PREIMPLANTATION GENETIC DIAGNOSIS
In recent years, developments in genetics allow genetic analysis to be carried out on embryos developed in vitro by in vitro fertilization ethods and the placement of selected healthy embryos in the uterus of the mother before pregnancy occurs. This method is called pre- regnancy genetic diagnosis (Preimplantation Genetic Diagnosis-PGD).
One of the most important application areas of the PGT technique embryos that do not have a genetic disease but may not have a genetic disorder in their chromosomes.
These disorders are more common in women of advanced age (35 years and older). This situation may result in infertility as it both reduces the chance of attachment of the embryo (implantation) and may cause unwanted abortions. As a matter of fact, 40 out of every 100 pregnancies in women aged 39 and over have problems that occur due to a numerical chromosomal disorder
The aim of PGD is to increase implantation rates, reduce spontaneous abortions and increase healthy baby birth rates by selecting hromosomally normal embryos. Indeed, the miscarriage rate, which can reach up to 23 percent in normal pregnancy due to chromosomal disorders, may decrease to 9 percent after PGD.
Pre-pregnancy genetic diagnosis is performed by taking 1 or 2 cells from embryos developed as a result of fertilization of egg and sperm cells obtained from mother and father candidates in laboratory environment. Special methods called Fluorescence In Situ Hybridization (FISH), Microarray-based comparative genomic hybridization (aCGH) or Polymerase Chain Reaction (PCR) are used for genetic diagnosis. Diagnosis of numerical chromosomal disorders such as monosomy or trisomy (Down syndrome and other trisomies) and single gene diseases (such as hemophilia, Mediterranean anemia, cystic fibrosis, muscular dystrophies) in the baby to be born is possible with PGD. Thus, healthy babies are born by transferring disease-free, healthy embryos to the expectant mother.
DIAGNOSIS BEFORE PREGNANCY
- In couples with a genetic or hereditary disease carrier,
- In couples who have a child or children with a previous genetic disease,
- For the purpose of HLA genotyping (tissue typing),
- In the identification of diseases showing genetic predisposition (tendency)
- Women in the advanced age group (37 years and over) who have been accepted for assisted reproductive techniques,
- In couples with recurrent early pregnancy miscarriages,
- In couples who could not achieve pregnancy with assisted reproductive techniques despite multiple applications or who lost their pregnancy due to miscarriage,
- It is applied in cases of chromosomal disorders or genetic diseases associated with severe male infertility.
HOW IS THE PGT TEST DONE?
- Whether the patient is suitable for PGD is evaluated by the reproductive health specialist, genetic counselor and the doctor of the related disease.
- The couple is prepared for the IVF procedure.
- The egg taken from the mother is fertilized in the laboratory with the sperm taken from the father.
- 1-2 blastomere cells are removed from the obtained embryo by biopsy by embryologists
- Cells obtained by biopsy are prepared and tested according to the method to be applied.
- Embryos with genetic diseases or chromosomal disorders are selected and discarded and healthy embryos are transferred to the mothers womb.
