Preimplantation Genetic Diagnosis, PGD
Patients facing known genetic risks for having a healthy baby now have treatment options through in vitro fertilization. Preimplantation genetic diagnosis (PGD) and preimplantation genetic screening (PGS) are laboratory procedures that, when coupled with IVF, can provide diagnostic information about the genetic health of an embryo prior to placement in the patient’s uterus in an attempt to establish pregnancy.
Preimplantation genetic screening (PGS) is performed to screen for embryonic abnormalities in chromosome number (aneuploidy) or structure (translocation) which commonly lead to implantation failure, pregnancy loss or birth defects. PGS methods are readily performed for most patients without significant advance preparations beyond those related to IVF. The cost of adding PGS to an IVF attempt is approximately $4,400.
Recent advances in the methodology also permit the evaluation of mitochondrial DNA, a portion of genetic material that is separate from the main package of nuclear DNA, which may further enhance the selection of an embryo with the best chance for success. Mitochondrial DNA testing adds on $500 to the above fee.
Preimplantation genetic diagnosis (PGD) is primarily performed to diagnose single gene defects in embryos that can lead to inherited disease in the fetus or offspring. This test is most relevant for couples who are both carriers for a known genetic disease such as cystic fibrosis.
PGD is also employed less often to avoid Rh factor incompatibility between Rh-sensitized mother and the intended offspring, or to identify HLA genes that match those of an existing sibling with hematologic disease.
PGD often requires the construction of DNA probes or materials specific to the genetic profiles of the parents and possibly grandparents which can take weeks to months prior to commencing treatment. Accordingly, fees for PGD are generally higher than for PGS.
PGS and PGD require the removal of a small number of cells (biopsy) from each embryo for the genetic test that will produce results in 2-15 days. The cells are taken from a small portion of the cellular layer that would develop into placenta. Recent studies indicate that embryo biopsy does not harm the ability of an embryo to establish pregnancy.
While the genetic analysis is performed, the embryos are maintained in cryopreservation storage at RMSCVA. After the genetic results are obtained, appropriate embryos may be selected for the eventual thaw and transfer into the uterus of the patient or a gestational carrier.