PGD improves pregnancy rates by identifying the presence of certain kinds of genetic disorders which can seriously affect the health of a baby. PGD/PGS testing are recommended for couples that have a family history of inherited disease or recurrent IVF failures, recurrent pregnancy loss, advanced maternal age or any genetic conditions.

PGD is performed on day 5 or day 6 of embryo development, also known as the "blastocyst" stage of embryo development. Trophectoderm biopsy on day 5 or 6 at the expanded blastocyst stage is a better way to do embryo biopsy. This process involves removal of cell from the trophectoderm, which is the tissue that can become placenta if the embryo implants after embryo transfer to the uterus.

Since the inner cell mass which can become a fetus after the embryo implants is not disturbed, trophectoderm biopsy minimizes the procedural risk to the embryo. Trophectoderm biopsy is less traumatic to the embryos than blastomere biopsy and therefore results in a higher success rate. Biopsy is performed and the embryos are frozen and subsequently thawed and transferred later after results of testing are available.