Pre implantation genetic diagnosis is a technique used to identify genetic defects in embryos created through in vitro fertilization (IVF) before transferring them into the uterus. Because only unaffected embryos are transferred to the uterus for implantation, Pre implantation genetic diagnosis provides an alternative to current post conception diagnostic procedures, i.e., amniocentesis or chorionic villus sampling, which are frequently followed by pregnancy termination if results are positive. PGD is performed in conjunction with IVF and is offered for both fertile and infertile couples.
Picture 1. Pre implantation Genetic Diagnosis Workup. (American Society for Reproductive Medicine, 1996)
Edwards and Gardner successfully performed the first known embryo biopsy on rabbit embryos in 1968. In humans, “PGD was developed in the United Kingdom in the mid 1980s as an alternative to current prenatal diagnoses” (Harper, 2001). PGD is presently the only option available for avoiding a high risk of having a child affected with a genetic disease without facing the dilemma of pregnancy termination following positive prenatal diagnosis. In 1989 in London, “Handyside and colleagues reported the first unaffected child born following PGD performed for an X-linked disorder” (Pergament, 1994).
As of May 2001, more than 3000 PGD clinical cycles have been reported. These cycles were performed at more than 40 centers around the world, and almost 700 children have been born, thus demonstrating the reliability and safety of the procedure. PGD is currently available for most known genetic mutations.
It has been well known that women experience an age related decline in the fertility rate starting at 35-36 years of age that carries across the type of treatment performed. Ultimately, “the decline in fertility observed in women over 40 years of age results in less than one half the fertility rate compared to women fewer than 40 as a group” (Lewis, 2000).......
