Preimplantation genetic diagnosis (PGD) is a form of genetic testing or genetic screening used with in vitro fertilization (IVF). Your physician may recommend PGD if there is a chance your embryos will be affected by certain chromosomal problems or a sex-linked disorder. These conditions can prevent implantation of embryos, lead to pregnancy loss, or result in the birth of a child with physical problems or mental retardation.
The PGD procedure allows genetic screening to be performed on early embryos prior to implantation and pregnancy development, thereby decreasing the likelihood of a chromosomal abnormality or sex-linked disorder.
Couples who elect PGD undergo an in vitro fertilization (IVF) cycle to create embryos. Before the embryos are transferred to the woman's uterus, genetic analysis is performed to identify embryos that do not carry the chromosome defect.
Preventive Measures During PGD Cycle
It is important for a couple undergoing PGD to alter their sexual activity during the PGD cycle. Beginning with day five of treatment with follicle stimulating hormones (FSH), the couple must refrain from sexual intercourse until cycle completion (regular menstruation or positive blood pregnancy test). Intercourse during this time could lead to a pregnancy with an embryo that has not been tested.
Risks of PGD
The biopsy technique required to perform PGD has been in use since 1990. The chance of accidental damage to an embryo during the removal of cells is very low. The risks of biopsy include decreasing the embryo’s chance for survival and continued development prior to implantation. Embryo biopsy is not known to lead to an increase in children born with congenital abnormalities, birth defects, mental retardation or other possible problems with development.
It is important to know that there may be no embryos available for embryo transfer, as PGD may reveal that all embryos are chromosomally abnormal. A normal pregnancy outcome cannot be guaranteed whether or not there is an embryo biopsy.
Accuracy of PGD
Overall, preimplantation genetic diagnosis is an accurate process for determining the chromosomal content of a cell from an embryo. There is a small risk of incorrect identification or unclear results in the biopsied embryo.
Some embryos are a mixture of normal and abnormal cells, called mosaicism. Because only one or two cells are taken for biopsy, the selected cells may not be representative of the embryo as a whole. For example, if a cell that has normal chromosomal content is analyzed, while other unanalyzed cells contain a chromosome abnormality, the embryo could be incorrectly diagnosed as normal. For many conditions, the option of testing early in pregnancy through prenatal diagnosis is available.
Cost of PGD
Preimplantation genetic diagnosis costs are in addition to the cost of in vitro fertilization and embryo transfer. They include the cost of the DNA probes, analysis, the biopsy procedure and professional physician and staff fees. There is a non-refundable fee for initial blood chromosome studies for both partners. Once a cycle has begun, there is an additional fee for PGD for translocations for each cycle.
Insurance companies generally do not cover the cost of PGD. Staff at the Reproductive Medicine Center can provide patients a detailed cost analysis for PGD.