Success Rates Newsletter 24-Hour Access for Patients Locations and Directions Referral HSG Services New Patient Forms Selecting a Physician Tubal Reversal Egg Donation Program Sperm Cryopreservation Minimally Invasive Surgery Recommended Links

Pre-implantation genetic diagnosis (PGD) is a technique used during In Vitro Fertilization procedures to screen the embryos for genetic or chromosomal disorders prior to transfer into the uterus. This screening may prevent the transmission of many heritable genetic and chromosomal disorders. PGD allows couples at high risk for having a child with a serious genetic or chromosomal abnormality to avoid giving birth to children with certain genetic disorders. The development of PGD has also enabled the pre-selection of chromosomally normal embryos for transfer, decreasing the chances of pregnancy loss. PGD requires specialized micromanipulation technology, equipment and experience. Coordination of genetic counseling, embryology/in-vitro fertilization (IVF) technology and molecular genetic analysis is necessary.

Procedure

To accomplish PGD, embryos are derived through IVF. The first stage of the procedure involves creating an opening in the zona pellucida (shell) surrounding the oocyte (egg) or embryo using micromanipulation techniques. Usually 3 days after fertilization, the embryo is composed of 6-8 cells (blastomeres). A single cell is obtained at this time, and is genetically evaluated. Removing this single cell will not compromise embryo development. The embryo is returned to the incubator.

Genetic Analysis

DNA from the biopsied cells is studied using the molecular techniques of polymerase chain reaction (PCR) and fluorescent in situ hybridization (FISH). PCR is used to detect monogenic disorders (see Table 1). DNA from the blastomere is isolated. The sequence of interest is amplified with PCR and then studied for presence or absence of the mutation. FISH is utilized to study chromosome number and in some cases, structure. The FISH technique involves the use of differently colored fluorescent probes, which attach to the chromosomes – the chromosome pairs are then analyzed.

Practical and Ethical Issues

The goal of a PGD cycle is the birth of an unaffected, healthy child. PGD has not yet been demonstrated to increase pregnancy/IVF success rates, and does add additional cost to the IVF procedure. To date, study of the approximately 1,000 children born in association with PGD has been reassuring, with no adverse outcomes experienced in excess compared to the general population. However, since the majority of these children are less than five years old, continued tracking and study is necessary. As such, the technique should be utilized to prevent the conception of children bearing significant genetic or chromosomal abnormalities. Public concern exists about the use of PGD for social reasons, such as sex selection. It is imperative that appropriate ethical guidelines are established and adhered to at centers offering PGD. Continuing efforts to develop methods to screen for a larger number of disorders are underway. Overall, PGD is becoming an increasingly valuable procedure offering at risk couples improved chances of carrying a healthy, unaffected child.

Table 1 Monogenic disorders for which PGD has been utilized

PLEASE CALL (813) 676-8825 TO SCHEDULE A CONSULTATION WITH ONE OF OUR PHYSICIANS TO LEARN MORE ABOUT PGD AND OTHER SERVICES OFFERED AT THE REPRODUCITVE MEDICINE GROUP.