Preimplantation genetic diagnosis (PGD) is a technique used to identify genetic defects in embryos created through in vitro fertilization (IVF) before transferring them into the uterus. PGD is performed in conjunction with IVF and is offered to fertile and infertile couples.
PGD combines recent advances in genetics and reproductive medicine. For preimplantation genetic diagnosis, the early embryo is examined after IVF for single gene defects, chromosomal disorders, or to determine the sex of the embryo for sex-linked genetic disorders. The process starts with a basic in vitro fertilization. When the embryo is at the 6- to 8-cell stage, 1-2 cells are removed and sent to the genetic laboratory for diagnosis using either polymerase chain reaction (PCR) or fluorescence in situ hybridization (FISH) techniques, depending on which disease is being sought. The healthy embryos are then transferred into the mother’s uterus.
PGD is recommended when embryos may be affected by a certain genetic condition. Only healthy and normal embryos are transferred into the mother’s uterus, thus preventing miscarriages, the need for pregnancy termination, or birth defects. Primary candidates for PGD include:
1. Couples in whom one partner has a family history of inheritable genetic disease or carries such a disease.
2. Women 35 years or older.
3. Women who have recurrent miscarriages.
4. Couples with repeated IVF failure.
5. Couples with chromosomal translocations, which can cause implantation failure, recurrent miscarriages, or mental or physical problems in offspring.
Preimplantation genetic diagnosis has many challenges including:
▪ Removal of a single cell without breaking it or causing serious damage is technically difficult.
▪ Not all chromosomal and genetic abnormalities can be diagnosed with PGD because only a restricted number of chromosomes can be examined at one time.
▪ Damage to the embryo may accidentally occur...