PGT

Preimplantation genetic testing (PGT) is a medical genetic technique used in conjunction with in vitro fertilization (IVF) to screen embryos for genetic abnormalities before they are transferred to the uterus. PGT encompasses several approaches: PGT-A for aneuploidy screening, PGT-M for known monogenic disorders, and PGT-SR for structural chromosomal rearrangements. The goal is to improve pregnancy outcomes by selecting embryos with a higher likelihood of healthy development.

The testing occurs after IVF and embryo creation. A few cells are biopsied from each embryo, typically at the blastocyst stage (trophectoderm) or less commonly at the cleavage stage. The genetic analysis uses a range of techniques, including fluorescent in situ hybridization (for some applications), polymerase chain reaction (PCR) for known mutations, and array-based methods or next-generation sequencing to detect chromosomal copy-number variations. Results are used to guide which embryos are transferred. Clinically, PGT is complemented by genetic counseling to discuss benefits, limitations, and potential outcomes.

PGT can reduce the risk of serious genetic diseases being passed to offspring and may decrease miscarriages related to chromosomal abnormalities. However, it has limitations: mosaicism can yield inconclusive or misleading results, not all conditions can be tested, and biopsy carries a small risk to the embryo. Turnaround times, access to specialized laboratories, cost, and ethical or regulatory considerations also influence its use. PGT is a screening tool, not a guarantee of a healthy pregnancy, and decisions about testing are made within a broader clinical and personal context.