Q: I read a wonderful story about how PGD (preimplantation genetic diagnosis) was used to create a sibling to help a child who needed a perfect bone marrow match to treat her rare disease. It’s hard to argue with that logic, but I’ve also read that PGD could be used in the future to let parents pick a baby’s gender or even other characteristics, such as eye and hair color. Is that true? Have you any experience with PGD and if so, what are the perks and when would an average couple want to consider it?
A: Our IVF laboratory in Atlanta has extensive experience with PGD. In fact, we were one of the first laboratories in this country to offer this service to patients. I frequently find myself in the position of counseling patients about the pros and cons of this technology to help them decide whether PGD is something they would want to consider. PGD is wonderful technology if used appropriately.
First, PGD requires IVF. Once the embryos are created, they are allowed to develop for three days until they are at the six-to-eight cell stage. At this point, one cell is removed from each embryo (embryo biopsy) for testing (which can take one-to-two days). The embryos are returned to the incubator until testing is complete, when the best embryos are selected for transfer to the mother’s uterus and hopefully a pregnancy ensues (no guarantees of course). Additional good quality embryos can be frozen for later use.
PGD should never be done without good reason. One should weigh carefully the benefits versus the risks of the procedure before deciding to do PGD. Although most good quality embryos tolerate embryo biopsy very well, some embryos may be slightly damaged by the biopsy procedure so that they slow in their development or stop altogether and cannot be used at all.
PGD is not used to create “designer babies.” PGD, at this moment, cannot determine eye or hair color and it will not be able to do so in the foreseeable future. Yes, it can tell you the sex of the embryo, but what PGD can do best is help people have healthy babies. Most of the time when PGD is done, it is done to detect abnormalities in the embryo. The removed cell is either tested for aneuploidy (extra or absent chromosomes) by FISH (fluorescent in situ hybridization) or for single gene defects by PCR (polymerase chain reaction) technology. Many inherited diseases can be detected in this way.
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