Preimplantation Genetic Testing (PGT)

What is PGT, PGD, PGS

PGT is pre-implantation genetic testing. It is a new term for both PGS/PGD. It is a procedure performed in the laboratory during an IVF cycle in order to detect/screen abnormalities in the chromosomes of the embryos (PGS, Pre-implantation genetic screening) or to test the embryo, before it implants for a known, specific genetic disorder, usually caused by a single gene disorder (PGD, Pre-implantation genetic diagnosis).

Appropriate candidates for PGT

• Advanced maternal age (>35 years)
• Couples who have experienced 2 or more IVF/ICSI cycle failures
• Couples who have had recurrent (2 or more) miscarriages/ recurrent implantation failures
• Male partner with severe male factor infertility
• Couples who have previously had a pregnancy with a chromosomal anomaly or a family history of an abnormal child
• Known genetic disorders in one or both parents or in either/both families

Steps involved

• Stimulation of the ovaries
• Collection of eggs from the ovaries
• Insemination or injection of sperm
• Fertilization
• Embryo biopsy
• Embryo testing
• Embryo freezing
• Embryo transfer following results

Benefits of PGT

• Reduces likelihood of conceiving a child with severe genetic disease
• Reduces miscarriages
• Increases chances of pregnancy, especially in advanced maternal age, recurrent miscarriages, recurrent implantation failure

Drawbacks of PGT

• Enough number of embryos may not be available on Day 5/6 for biopsy.
• More than one stimulation cycle might be required for embryo pooling
• The biopsied cells might not be representative of the cells that form the fetus
• Normal results might result in an abnormal embryo (so prenatal diagnostic tests are mandatory)
• High cost & mandatory genetic counselling