Page "Preimplantation genetic diagnosis" Paragraph 1

The term pre-implantation genetic screening ( PGS ) is used to denote procedures that do not look for a specific disease but use PGD techniques to identify embryos at risk.

PGD is a poorly chosen phrase because, in medicine, to " diagnose " means to identify an illness or determine its cause.

An oocyte or early-stage embryo has no symptoms of disease.

They are not ill. Rather, they may have a genetic condition that could lead to disease.

To " screen " means to test for anatomical, physiological, or genetic conditions in the absence of symptoms of disease.

So both PGD and PGS should be referred to as types of embryo screening.