What Is Pre-implantation Genetic Testing?
How is the PGD performed?
Pre-implantation genetic diagnosis begins with the normal process of in vitro fertilization that includes egg retrieval and fertilization in a laboratory. Over the next three days the embryo will divide into eight cells.
Preimplantation genetic diagnosis involves the following steps:
• First, one or two cells are removed from the embryo.
• The cells are then evaluated to determine if the inheritance of a problematic gene is present in the embryo.
• Once the PGD procedure has been performed and embryos free of genetic problems have been identified, the embryo will be placed back in the uterus, and implantation will be attempted.
• Any additional embryos that are free of genetic problems may be frozen for later use while embryos with the problematic gene are destroyed.
Who might benefit from PGD?
Preimplantation genetic diagnosis can benefit any couple at risk for passing on a genetic disease or condition.
The following is a list of the type of individuals who are possible candidates for PGD:
• Carriers of sex-linked genetic disorders
• Carriers of single gene disorders
• Those with chromosomal disorders
• Women age 35 and over
• Women experiencing recurring pregnancy loss
• Women with more than one failed fertility treatment
PGD has also been used for the purpose of gender selection. However, discarding embryos based only on gender considerations is an ethical concern for many people.
What are the benefits of PGD?
The following are considered benefits of PGD:
• PGD can test for more than 100 different genetic conditions.
• The procedure is performed before implantation thus allowing the couple to decide if they wish to continue with the pregnancy.
• The procedure enables couples to pursue biological children who might not have done so otherwise.
Human eggs are often chromosomally abnormal – and the percentage of eggs with a chromosomal abnormality increases with increasing female age. In general, about 30 to 60 per cent of human embryos have some type of chromosomal abnormality. This increases significantly with advancing female age.