The PGD Procedure
Pre-implantation genetic diagnosis (PGD) is a technology that allows analysis of the genetic make-up of the early embryo before it is transferred into the uterus. PGD is similar to other invasive prenatal screening tests. Namely, it is done prior to implantation of the early embryo.
PGD is able to detect three basic genetic characteristics in the embryo
- Chromosomal aneuploidy – an abnormal number of chromosomes (e.g. Down’s Syndrome, Trisomy 13, Trisomy 18, Turner’s Syndrome.)
- Single gene defects – specific genetic mutations leading to known diseases (e.g. Cystic fibrosis, Tay-Sachs, Thalassemia.)
- Gender (male or female)
In order for PGD to be performed, couples must undergo IVF with or without ICSI to allow for the formation of early embryos in the laboratory. When embryos are three days old (typically containing 7-8 cells), PGD is performed by inserting a tiny needle into each embryo and removing 1 or 2 cells (called blastomeres). Various techniques of gene amplification and chromosomal analysis are next applied in order to analyze removed blastomeres for their genetic make-up. Embryos determined to be abnormal, or of the wrong gender (in the case of sex linked genetic diseases, or for sex selection purposes), are discarded. Normal embryos are transferred into the uterus within 24 hours of the procedure. Numerous animal and human studies have documented the safety of PGD and its benefits in assuring that a healthy embryo is chosen for transfer.
Who are candidates for PGD?
Couples who are known carriers of specific genetic mutations or who have p reviously had a genetically affected child have a significantly increased risk of having a genetically affected offspring .
Couples who are known carriers of a chromosomal aberration such as a translocation have a significantly increased risk of recurrent pregnancy loss and implantation failures.
Women of advanced reproductive age and couples who have had recurrent pregnancy loss due to chromosomal aneuploidy .
Couples who have several children of one gender and are interested in sex selection/family balancing .
CIA offers all PGD services. For more information, please contact us at any time
What is PGD?
There are two types of PGD. The first technique screens couples who have a known risk for inherited diseases such as cystic fibrosis, Tay-Sachs, muscular dystrophy, chromosomal translocations among others. The second screens for aneuploidy to test for common chromosomal abnormalities associated with advanced maternal age, repeated IVF failures or recurrent pregnancy loss.
PGD is a highly sophisticated procedure that is offered by a limited number of facilities. Some centers limit its availability to couples who have experienced repeated miscarriages due to genetic disorders or who have already had one pregnancy/child with a genetic disorder and face the same high risk in subsequent pregnancies. Some centers make the procedure available to women of advanced reproductive age.
Since PGD is time sensitive, only available in a few clinics and the process requires advanced preparation, couples considering PGD should make arrangements well in advance of their IVF cycle.