Preimplantation Genetic Diagnosis
The earliest diagnosis of genetic diseases — PGT/PGS
The earliest diagnosis of genetic diseases is possible with preimplantation genetic diagnosis. Preimplantation Genetic Diagnosis, or PGT/PGS for short, is a method that allows embryos to be examined hereditarily and genetically. For couples who are carriers of genetic diseases to have healthy babies, embryos obtained through IVF or microinjection are evaluated with genetic testing, and healthy embryos are selected and transferred to the mother's womb. The aim here is to prevent the transmission of chromosome anomalies, reduce the risk of miscarriage and select genetically healthy embryos. With preimplantation genetic diagnosis, the loss of the baby due to diseases that may arise from birth or later can be prevented, and families carrying genetic diseases can be enabled to have healthy children.
Who Should Undergo PGT/PGS Testing?
- Expectant mothers aged 36 and over
- Couples who have had two or more IVF attempts without achieving pregnancy
- Couples with recurrent early pregnancy losses (miscarriages) not due to translocation carrier status
- Couples who are balanced translocation carriers
- Couples at risk for certain single-gene diseases that can be diagnosed, such as Familial Mediterranean Anemia, Sickle Cell Anemia, Cystic Fibrosis and SMA
- Selection of an embryo HLA-compatible with family members
- Couples who have had a child with a genetic disease from a previous pregnancy
- Mothers with a history of aneuploid (chromosomal disorder) pregnancy
- Cases of gonadal mosaicism (where the partners' genetic test results are normal despite two or more births with the same abnormality)
- TESE cases (cases accompanied by severe male infertility)
- Poor responders (cases with insufficient response to the hyperstimulation protocol)
- For diseases showing X-linked inheritance; determination of embryo sex if direct genetic diagnosis of the disease in question is not possible
What Are the Benefits of PGT/PGS?
- It increases the chance of success of IVF treatment.
- It increases the clinical pregnancy rate.
- It reduces the risk of pregnancy ending in miscarriage.
- It reduces the need for medical termination of pregnancy.
- It reduces the rate of multiple pregnancy.
- It reduces the financial burden and psychological pressure of recurrent failed IVF attempts.
How Is the PGT/PGS Method Performed?
- To perform preimplantation genetic diagnosis, a cell sample must be taken from each of the patient's embryos. During PGT application, the possibility of harm to the embryos is negligibly low (the damage rate has been determined as 0.3%).
- After classical IVF treatment stimulation, the collected eggs are combined with sperm by applying the microinjection method on the same day, and the resulting embryos are monitored until the blastocyst stage.
- A biopsy procedure is performed on your embryos on the 3rd day (one or two cells are removed from each embryo). This procedure does not harm your embryos.
- The genetic test results of your embryos can be obtained within 6-12 hours.
- Embryos determined to be healthy are reported for transfer to the expectant mother.
- The transfer of healthy embryos that do not carry the disease in question starts the mother on a healthy pregnancy.
The Newest Method Used for Preimplantation Genetic Diagnosis: NGS
With Preimplantation Genetic Diagnosis (PGT), a method applied for about 20 years, initially five different chromosomes (13, 18, 21, X, Y or 13, 16, 18, 21, 22) could be examined with the FISH method, and over time this number increased to 9 chromosomes. In recent years, 24 chromosome screening began using microarray (aCGH) technology, and immediately afterwards, from 2015 onwards, the NGS technique took its place in IVF applications and spread rapidly.
NGS (Next Generation Sequencing), the abbreviated form of the New Generation Sequencing definition, which we prefer for our patients as the most accurate, most reliable and most current technique, is a new genetic testing method used for 24 chromosome screening in embryos. NGS, which can be described as a revolutionary DNA sequencing technology in genetic research, enables the entire human genome to be examined and sequenced both numerically and structurally within a short period of time such as a single day.
The NGS method can detect mosaic embryos better compared to other PGT methods. In addition to the ability to screen a very wide gene area both numerically and structurally, its other advantages are obtaining more definitive results with a low error margin, reaching results faster and lower cost. Moreover, when this method is used, single-gene disease testing and HLA typing can be performed together with 24 chromosome screening at the same time.