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Pre-implantation genetic diagnosis (PGD) is a laboratory procedure — used in conjunction with in vitro fertilization (IVF) — to evaluate the risk of passing on genetic conditions, such as cystic fibrosis or sickle cell anemia, or structural changes in chromosomes.

Typically, couples in need of this screening are not infertile but have a family history of a disease and want to reduce the risk of passing on the condition. Some couples are found to be at risk for an inherited condition when undergoing routine genetic screening for fertility treatment and seek PGD in the course of their care.

Families also may use PGD when considering having a child who can provide matching stem cells as a bone marrow donor.

PGD is available for almost any inherited condition for which the exact mutation is known. A unique test must be developed for each couple. This test design may take several months to complete before beginning an IVF cycle.

PGD uses IVF, where multiple eggs are matured and retrieved. The oocytes — or primitive egg cells — are inseminated with a single sperm using intracytoplasmic sperm injection (ICSI).

The resulting embryos are grown in culture until the six-to-eight-cell stage, which is day three of embryo development. At this point, the embryo is biopsied with the removal of one to two cells. This process does not damage the cells remaining within the fertilized egg.

The isolated cells are evaluated for the specific genetic conditions anticipated. Embryos that are unaffected are transferred back to the woman's uterus on day five of embryo development.

Two main techniques are used for the genetic assessment:

• Polymerase chain reaction (PCR) — In this process, multiple copies of the gene of interest are made by a process of amplification. This amplification process allows the identification of very small amounts of DNA to make the diagnosis.

• Fluorescent in situ hybridization (FISH) — FISH allows the laboratory to count the number of chromosomes in an isolated cell. This technique is used primarily for expected abnormalities in chromosome number, such as in Down syndrome, or translocations, which affect the structure of the chromosome.

At UCSF Medical Center, our embryology laboratory staff has extensive experience with embryo micromanipulation and biopsy. A genetic counselor is available to coordinate your cycle with the IVF team and the PGD laboratory to make the process as smooth as possible.

For more information or a consultation, please contact:
Pre-implantation Genetic Diagnosis Program (415) 353-7397