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Preimplantation genetic diagnosis (PGD) is a state of the art procedure used in conjunction with in vitro fertilization (IVF) to select embryos free of chromosomal abnormalities and specific genetic disorders for transfer to the uterus. These genetic conditions can interfere with embryo implantation and may even result in pregnancy loss, or in the birth of a child with physical problems, developmental delay or mental retardation.
There are three similar terms which are often confused: preimplantation genetic testing, diagnosis and screening. The easiest way to understand the differences is to remember that the “testing” refers to the identifying techniques themselves, while the diagnosis (PGD) is when one or both parents has a known genetic abnormality or is at increased risk (see indications below)– and testing is indicated and performed on the embryo(s). Conversely, the “screening” (PGS) refers to the screening of embryos from presumed chromosomally normal genetic parents.
PGD is performed as a part of an In Vitro Fertilization cycle where multiple eggs are produced, retrieved from the ovaries and fertilized with the partner’s sperm in the Embryology Laboratory. IVF is necessary to provide access to the embryo in vitro on day 3 post-retrieval (~8 cells). One or two cells are removed from each embryo through a procedure called embryo biopsy. These cells are analyzed in the PGD Laboratory to determine which embryos are free of genetic abnormalities. This sophisticated and technologically advanced testing identifies which embryos are free of abnormalities and more able to achieve the patient’s goal of a healthy baby.
PGD may be recommended by your physician when there is a possibility (indicated by your medical history or advanced maternal age) that your embryos could be affected by a genetic disease. PGD testing can only be performed within the context of an IVF cycle where eggs and sperm, united in the laboratory, develop into embryos. Reproductive Resource Center of Greater Kansas City offers PGD screening for chromosome disorders and single gene defects.
Potential Indications for PGD
- Inherited genetic disorders
- Recurrent Miscarriage
- Advanced Maternal Age
- Unexplained Infertility
- Unsuccessful IVF Cycles
Today, PGD technology reduces the potential for adverse pregnancy outcomes for couples “at risk” by enabling us to test the embryos for certain genetic abnormalities before they are chosen for transfer back to the woman. For example: 10 embryos resulted from an IVF cycle and through PGD testing, 6 were identified as genetically abnormal and four were normal. Armed with this knowledge, only the normal embryos would be selected for embryo transfer thereby reducing the possibility of miscarriage or birth defects.
In case you missed it, you’ll want to read our earlier post about RRC Embryologist Michelle Kiehl. Michelle recently attended the annual American Society for Reproductive Medicine (ASRM) meeting in Denver and spoke at length with us about what she learned– particularly in the area of embryology.
*Pictured is Derica, one of our talented Embryologists, busy at work!