PGD

Preimplantation genetic diagnosis (PGD) is a reproductive technology used with in vitro fertilization (IVF) to detect genetic abnormalities in embryos before implantation. PGD is typically pursued by couples with a known genetic risk, or those seeking to reduce the chance of hereditary disease in their children. The aim is to select embryos that are healthy for transfer to the uterus.

In an IVF cycle, eggs are fertilized to form embryos. A few cells are biopsied from the embryo at the blastocyst stage (usually day 5) or earlier, and DNA is analyzed for specific mutations or chromosomal abnormalities using methods such as PCR, FISH, array-based testing, or sequencing. Embryos deemed to be free of the targeted conditions are transferred, while others may be frozen for later use.

Applications include preventing single-gene disorders (for example recessive or dominant mutations), reducing aneuploidy-related miscarriage, and, in some cases, HLA matching to produce a donor child. PGD does not guarantee a healthy baby and may miss mosaicism or mutations outside the tested scope. It also raises ethical questions about embryo selection and access.

Risks and limitations include the invasive embryo biopsy, potential for diagnostic error, residual risk of disease, cost, and variable success rates. Guidelines emphasize genetic counseling and informed consent. The availability and regulation of PGD vary by country, reflecting differing medical standards and ethical norms.