What is pre-implantation genetic diagnosis (PGD)?
PGD is performed when patients have a family history of a genetic disease or are carriers of a gene mutation and as a result, have an increased chance to have a child affected with a genetic disease. The aim of PGD is to provide patients at risk of passing on a genetic disorder to their children the chance to have an unaffected pregnancy. The purpose of PGD is to identify affected embryos at a very early stage and avoid transferring them, thus preventing them from implanting in the womb. The effect of such a procedure is to increase the probability that embryos that implant and create a pregnancy will be unaffected by the specific disease tested. Preimplantation analysis is not yet considered to be a standard technique and consequently it is recommended that patients who become pregnant undergo prenatal testing using CVS or amniocentesis.
Who should consider having PGD?
- People with a family history of X-linked disorders
- People with chromosome translocations, which can make it difficult for an embryo to implant in the uterus, may cause recurrent pregnancy loss, or lead to mental or physical conditions in the offspring
- Carriers of autosomal recessive diseases (For carriers of autosomal recessive diseases, the risk an embryo may be affected is 25%.)
- Carriers of autosomal dominant diseases (For carriers of autosomal dominant disease, the risk an embryo may be affected is 50%.)
Those interested in PGD =/- PGS should be referred to Mount Sinai Fertility. An appointment with a Genetic Counsellor will also take place.
In terms of the cycle itself, the entire procedure consists of five different steps, usually performed by different experts and laboratories:
- Patients having PGD +/- PGS undergo ovarian stimulation and IVF-ICSI to create embryos. This part will take place at Mount Sinai Fertility.
- The second part involves embryo biopsy performed by an embryologist at Mount Sinai Fertility. The biopsy, which takes place at the appropriate stage for the ordered testing, is done to remove material from the embryo.
- The biopsy samples are then transported to the appropriate genetics reference laboratory.
- The genetics reference laboratory analyses the biopsy samples.
- Should there be embryos for transfer, this will take place at Mount Sinai Fertility no sooner than the next month after the IVF cycle. Usually the embryos are frozen after biopsy. A frozen, thawed embryo transfer is planned in the next month if genetic testing demonstrates at least one unaffected and/or chromosomally normal (euploid) embryo for transfer.