Preimplantation Genetic Diagnosis | PGD

Pre-implantation genetic diagnosis

Pre-implantation genetic diagnosis (PGD ) is the genetic profiling of embryos prior to implantation (as a form of embryo profiling), and sometimes even of oocytes prior to fertilization. PGD is considered in a similar fashion to prenatal diagnosis. When used to screen for a specific genetic disease, its main advantage is that it avoids selective abortion, as the method makes it highly likely that the baby will be free of the disease under consideration. PGD thus is an adjunct to assisted reproductive technology, and requires in vitro fertilization (IVF) to obtain oocytes or embryos for evaluation. Embryos are generally obtained through blastomere or blastocyst biopsy. The latter technique has proved to be less deleterious for the embryo, therefore it is advisable to perform the biopsy around day 5 or 6 of development.
It prevents the transmission of diseases such as Cystic Fibrosis, Thalassaemia or Muscular Dystrophy, among many others.

Pre-implantation genetic diagnosis Process

Genetic study
After in vitro fertilization, and before the transfer to the uterus, the genetic material of the embryo is studied in order to detect genetic alterations.

biopsy
A biopsy is performed on each embryo or eggs and those which have a specific congenital disease are discarded.

Transfer
One to two healthy embryos are transferred. The healthy embryos can be frozen.

The PGD can be obtained in two different ways

Preimplantation Genetic Diagnosis with embryos

This study is done when the embryos are preferably at the blastocyst stage or at the 6-8 cell phase, depending on embryo quality and quantity. To study their genetic material, a biopsy is carried out on each one. Those with a genetic disease are discarded and only the healthy embryos are selected, which are the ones that are transferred to the uterus.

Preimplantation Genetic Diagnosis with eggs

This technique allows us to detect genetic or chromosomal diseases in the egg, before the embryo is formed. A part of the egg, the so-called polar corpuscle, is analyzed, so only hereditary pathologies from the mother can be detected. A biopsy is done, and once the polar corpuscle is removed, the oocytes are inseminated with the intracytoplasmic sperm injection (ICSI). After two days, the genetic result is obtained and the embryos from the healthy oocytes are selected for transfer.