Preimplantation Genetic Diagnosis (PGD / PGT / PGS)

The earliest diagnosis of genetic disorders is possible through Preimplantation Genetic Diagnosis. Preimplantation Genetic Testing (PGT/PGS) is a method that allows embryos to be analyzed genetically and hereditarily. Embryos obtained via in vitro fertilization (IVF) or microinjection from couples who are carriers of genetic disorders are examined, and healthy embryos are selected for transfer to the uterus. The goal is to prevent the transmission of chromosomal abnormalities, reduce the risk of miscarriage, and select genetically healthy embryos. This process helps prevent loss of the baby due to genetic disorders after birth or later in life and enables families carrying genetic diseases to have healthy children.

Who Should Undergo Preimplantation Genetic Testing?

• Women aged 36 and above

• Couples who failed to achieve pregnancy despite two or more IVF attempts

• Couples with recurrent early pregnancy losses (excluding balanced translocation carriers)

• Couples who are balanced translocation carriers

• Couples at risk for certain single-gene disorders (e.g., Beta-thalassemia, Sickle Cell Anemia, Cystic Fibrosis, SMA)

• Couples needing HLA-compatible embryo selection

• Couples who have had a previous child with a genetic disorder

• Women with a history of aneuploid pregnancies

• Cases of gonadal mosaicism (normal parental genetic tests but abnormal offspring)

• TESE cases (severe male infertility)

• Poor responders to ovarian stimulation protocols

• For X-linked disorders, if direct genetic diagnosis of the disease is not possible, embryonic sex determination may be performed

Benefits of PGT/PGS

• Increases the success rate of IVF

• Raises the clinical pregnancy rate

• Reduces the risk of miscarriage

• Minimizes the need for medically indicated pregnancy termination

• Reduces the incidence of multiple pregnancies

• Decreases financial and psychological burden from repeated IVF failures

How is PGT/PGS Performed?

Cells are biopsied from each embryo without significant risk (damage rate ~0.3%).

After standard IVF stimulation, eggs are fertilized using microinjection and cultured to the blastocyst stage.

On day 3, a biopsy is performed (1–2 cells removed per embryo), which does not harm the embryos.

Genetic testing results are available within 6–12 hours.

Healthy embryos are selected for transfer, starting a pregnancy with minimal risk of genetic disorders.

NGS: The Latest Method for Preimplantation Genetic Testing

Initially, FISH was used to analyze 5 chromosomes (e.g., 13, 18, 21, X, Y).

Later, microarray (aCGH) enabled testing of all 24 chromosomes.

Since 2015, Next-Generation Sequencing (NGS) has become widely used in IVF.

Advantages of NGS:

Highest accuracy and reliability

Can detect mosaic embryos better than other methods

Allows simultaneous analysis of single-gene disorders, HLA typing, and 24-chromosome screening

Low error rate and faster results

Cost-effective compared to older techniques

NGS is a revolutionary DNA sequencing technology that can analyze the entire human genome both structurally and numerically in a very short time, offering precise and comprehensive preimplantation genetic testing.