Explaining PGD: Preimplantation Genetic Diagnosis
A normal embryo must have forty-six chromosomes in the correct combination to be viable. As a woman ages, the number of eggs remaining in her ovaries decrease and the ones that remain are more likely to give rise to embryos with abnormal chromosome counts (aneuploidy). Preimplantation Genetic Diagnosis (PGD) is a method used to screen embryos for aneuploidy. The biopsied cell then undergoes genetic or chromosomal analysis.
In this technique, a few cells are safely removed from the embryo when it is 5-6 days old (called a blastocyst). The biopsied cells then undergo chromosomal analysis. We use very accurate genetic methods to analyze the cells such as Comparative Genomic Hybridization (CGH). The gender of the embryo can also be determined at the same time.
PGD also makes it possible to select gender, a procedure we discuss in greater detail in the gender selection section of this website. For more information, please see gender selection.