To PGD or Not to PGD by Corey Senn For some couples, it's the right recipe for healthy babies  print article      send to a friend

De-Mystifying PGD

PGD starts off like a regular in vitro fertilization (IVF). "I had to take all the regular fertility shots and get my hormones to a level where they could harvest my eggs," says Tiffany. At that point, her unfertilized eggs were fertilized in a laboratory using her husband's sperm. On the third day after fertilization, a single cell was removed from each embryo.

At this point in the process, a series of tests are run to check for diseases or defects that a couple may carry. On day 5, the clinic can tell which embryos, if any, are affected by a particular disease or defect. The healthy embryos are then reinserted into the woman's uterus through a simple and painless procedure.

Most people have some idea whether they are carriers of a particular genetic or chromosomal disease, either through a family history of the disease; having had a child born with a disease; through routine health exams; or because of their ethnic/racial group. For instance, cystic fibrosis is the most common genetic disorder among Caucasians, Tay-Sachs afflicts many within the Jewish community, and sickle cell anemia is prevalent among African-Americans. But as Michael Feinman, MD, of the Westlake Village, California based Huntington Reproductive Center points out, "most couples opt for PGD because they have had a child that was affected with the disease or a pregnancy that was affected by the disease."

Who Can Benefit?

PGD tests three basic groups (see accompanying table). The first is those who suffer from a single gene defect. These diseases include, among others, Tay-Sachs, sickle cell anemia, muscular dystrophy, hemophilia, and cystic fibrosis.

PGD is also ideal for anyone with a chromosomal defect. Infertility specialists use special stains, or probes, to check for the five or six most common chromosomal abnormalities. By far, the most common defect of this kind is Down's syndrome. Chromosome testing is particularly important for women over 35--when the incidence of chromosomal defect increases.

If one member of a couple has a chromosomal rearrangement, known as a balanced translocation, the couple may also benefit from PGD. A balanced translocation is often responsible for a woman experiencing multiple miscarriages.

The Limits of Testing

PGD cannot detect every genetic disease yet; scientists have not yet cracked the code for certain disorders, such as multiple sclerosis. Yet, according to Sue Gitlin, M.S., a member of the research faculty at the Jones Institute of Infertility (associated with the Eastern Virginia Medical School), "As long as we know what the specific genetic cause is for the disease, then we have the capability of trying to incorporate a test that is sensitive enough to detect for this in a single cell." As scientists continue to decode more and more genes, they will be able to detect an ever-increasing number of diseases.

PGD will never be 100% accurate. "The reason why we have this limitation is because we're working with one or two cells from an embryo. We can't go back and do the things that they can when they have hundreds of cells (as with an amniocentesis)," explains Gitlin. But to put things into perspective, neither the Jones Institute of Reproductive Medicine (which has performed PGD since 1993) nor the Huntington Reproductive Center (which diagnoses 5-10 PGD cases per week) has ever made a misdiagnosis.

The cost of PGD is roughly $3,500 above and beyond a normal in vitro fertilization cycle. For Tiffany and Steven Doctors, the entire cost of the IVF and PGD testing was $11,000. But don't assume the price tag means clinics are getting rich off of PGD. The equipment and testing is expensive--the biggest payoff for the clinics is helping couples to have healthy children. And while these costs may seem high, doctors point out that they are nothing when compared to the cost of caring for a child with a serious genetic disorder.

The Benefits of PGD

PGD essentially protects a couple from having a child with their problematic genetic or chromosomal history. For the Doctors, PGD revealed that two of their embryos were affected. These would have been children born with Tay-Sachs disease. Without PGD, couples are essentially "playing the odds" as to whether or not they will have an affected child. (If both parents are carriers of a disease, they have a 25% chance of having an affected child.)

PGD also saves couples from having to choose whether to end a pregnancy of a child they know will be born with a debilitating disease. As Dr. Feinman points out, "For a certain group of people, PGD offers a new way to prevent disease without having to face a termination of pregnancy--obviously a very emotional and difficult choice." This is not to say that couples that decide not to terminate a pregnancy will love their child any less. But the fact is a child born with a debilitating disease presents a whole new set of emotional and physical challenges for everyone involved. "We have a son that experienced our daughter's death at a very young age," explains Tiffany. "There would be no way we would want to put him through all that again. To have a beautiful, healthy child--it's an amazing thing they can do with PGD."

In April of this year, with the help of PGD, Tiffany Doctors gave birth to a healthy baby girl.