Preimplantation Genetic Diagnosis

At Yale, it is possible to increase the chance of successful pregnancy through a technique known as PGD—preimplantation genetic diagnosis.

PGD 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, PGD provides an alternative to current postconception diagnostic procedures, 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.

During the process

One single cell from an eight-cell embryo is removed and analyzed using a procedure called FISH (fluorescence in situ hybridization). This procedure allows us to examine whether an embryo has the correct chromosome numbers and can, for example, help detect embryos that have a high chance of carrying an extra chromosome 21 (Down's syndrome) or other common chromosomal problems that could lead to miscarriage.

We can currently examine 9 of the 23 chromosomes (chromosomes X, Y, 13, 15, 16, 17, 18, 21, and 22), but we are feverishly researching new techniques to have an accurate rapid assessment of all the chromosomes.

When can PGD help?

• Advanced maternal age: It is known that women approaching 40 are at a higher risk of having a baby with a chromosome abnormality (most notably Down's syndrome). With PGD, embryos are tested for chromosome defects before being transferred into the uterus.
• Multiple IVF failures: Failure to achieve a pregnancy after multiple cycles of IVF with embryo transfer can leave couples in a distressed state. PGD may help answer the question of why the embryos aren't implanting.
• Recurrent spontaneous miscarriages: To reduce the risk of recurrent spontaneous abortions or miscarriage in couples where one or both are carriers of chromosomal defects (balanced translocations).
• Genetic disease: To avoid the risk of transmitting genetic disease when one or both parents have a genetic disease such as hemophilia or muscular dystrophy that could be transferred to offspring.