Preimplantation Genetic Diagnosis (PGD)
Preimplantation genetic diagnosis (PGD) is a way to test embryos for genetic defects prior to performing an embryo transfer. PGD was developed in the early 1990′s and has recently undergone many improvements. We are now able to evaluate all chromosomes in a comprehensive manner that was nto available until recently.
PGD is a way for patients undergoing In Vitro Fertilization (IVF ) to prevent a pregnancy affected by a genetic condition or chromosomal disorder. There are various types of PGD available, depending on the needs of the individual couple. The specific type of PGD required should be discussed with your physician.
The embryos that are found to be normal are transferred into the uterus and have a high likelihood of implanting and resulting in the birth of a healthy baby.
The Different Types of PGD Available.
- Comprehensive Chromosomal Screening (CCS) where all chromosomes are evaluated to make sure that there are 2 of all chromosomes present –plus an XY for a male or an XX for a female embryo.
- Limited chromosomal screening –typically looking at 3 to 5 chromosomes (usually X, Y, and 21). This can evaluate sex chromosomal abnormalities and chromosomal 21 abnormalities (Down’s Syndrome).
- Single Gene Disorders. This is used when there is a genetic disorder that runs in a family and when one of the patients undergoing IVF is found to be a carrier or affected by this gene. In order to prevent this disease from affecting other individuals, PGD can be done to select those embryos that do not carry the affected gene. Examples of single gene disorders include: cystic fibrosis, sickle cell disease, thallasemia, Tay-sachs disease, Huntington disease, and many others. Almost any genetic disorder that can be linked to a specific gene can by identified using PGD.
Who Can Benefit from PGD?
PGD can benefit any couple at risk for passing on a genetic disease or condition. The procedure is performed prior to implantation so the need for amniocentesis later in pregnancy is reduced or negated. Mostly commonly PGD is used by women age 35 and over, carriers of genetic disorders, women experiencing recurrent pregnancy loss, or any patient desiring to ensure the transfer of chromosomally normal embryos. Some couples will also use PGD for family balancing or gender selection which like any form of PGD has an important medical utility to avoid sex chromosome-linked diseases like hemophilia and Duchenne’s muscular dystrophy.
For more information about IVF and PGD please contact our office.