This document provides an overview of preimplantation genetic diagnosis (PGD). PGD is an in vitro fertilization procedure that tests embryos for genetic conditions before implantation. It was first reported in 1990 and combines advances in genetics and assisted reproduction. The document discusses the indications for PGD, including chromosomal disorders and monogenic diseases. It also describes the technical processes involved, such as blastomere biopsy and genetic analysis using fluorescence in situ hybridization, array comparative genomic hybridization, and polymerase chain reaction. Both the benefits and risks of PGD are outlined.