Preimplantation Genetic Testing (PGT-A) | Dr. Hakan Özörnek

Preimplantation Genetic Testing (PGT-A)

In contemporary IVF treatment, the newly implemented preimplantation genetic testing (PGT-A) allows both patients and carrier couples to have healthy babies. During IVF treatment, embryos obtained by fertilizing eggs with sperm can be screened for many familial and chromosomal diseases through the sampling of 1 or 2 tissues (blastomeres) before being implanted into the mother's uterus.

Couples carrying chromosomal or genetic diseases, even if they do not have issues like infertility, can have healthy children through IVF treatment and the subsequent application of PGT to embryos. This process involves taking 1 or 2 tissue samples from embryos formed by fertilizing eggs from the mother with sperm from the father during IVF treatment. These samples are then tested, and the embryos identified as healthy are implanted into the mother's uterus.

PGT-A is particularly recommended for diseases that are inherited and cannot be treated after birth. The first PGT-A baby was born in the United States in October 2000, and this method was used to select and transfer the only healthy embryo from about 15 embryos in that pregnancy.

PGT-A, which began to be applied in the late 1990s in the United States and Europe, is used in our center for patients deemed necessary. If there are recurrent miscarriages, failed IVF attempts, advanced age, or genetic or chromosomal diseases (disease or carrier status) in one of the partners, the use of the PGT-A method may be recommended. This method involves selecting and transferring embryos that are healthy and do not carry genetic diseases. For example, the occurrence of ornithine carbamoyltransferase deficiency, a disease causing liver disease and transmitted from the mother to the baby through the X chromosome, can be prevented by selecting and implanting embryos that do not carry this disease using the PGT-A method in IVF treatment.

In today's world, conditions such as hemophilia, Duchenne and muscular dystrophy, Tay-Sachs, cystic fibrosis, sickle cell anemia, fragile X syndrome, Down syndrome, and some other chromosomal diseases can be diagnosed using the PGT-A method.

The result of the PGT-A method, which is applied without harming the embryos, can be obtained within 2 weeks. This method can be performed through:

  • Polar body biopsy from maternal ovaries (oocyte) (can detect diseases specific to the mother only).
  • Tissue sampling from a 3-day-old embryo (6-8 cells) (blastomere biopsy) (most commonly used method in practice).
  • Tissue sampling from a 5-day-old embryo (blastocyst biopsy). The array CGH method is currently used for genetic diagnosis, allowing the complete numerical identification of all 46 chromosomes in humans.

Research is ongoing for the future possibility of detecting genetically inherited diseases such as cardiovascular diseases, diabetes, hypertension, and cancers using the PGT method. The goal is to eradicate these diseases entirely in future generations.

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