What’s Preimplantation Genetic Diagnosis?
Preimplantation genetic diagnosis, or PGD, is a technique that can be used as part of in vitro fertilization (IVF). It allows the genetic testing of embryos, so that only those embryos that are healthy are transferred into the uterus. This may increase the chances of a successful pregnancy, since embryos that have a chromosomal or other major genetic abnormality, and would therefore not be capable of developing into a viable baby, will not be transferred. It also allows the intended parents to avoid passing on certain genetic diseases to their children, since only those embryos that are free of the disease will be transferred.
If you’re choosing IVF with PGD, make sure you’re choosing it because you really want it, not to please someone else or to fit an imagined ideal. No one else can make the choice for you; it’s your body, and you’re in charge of it. After you do your research and understand the procedure, if you believe that PGD is right for you, then proceed. To help you in your decision-making process, we have some information about the risks and benefits of having PGD at Preimplantation Genetic Diagnosis (PGD): Risks and Benefits.
Please note that this page is for informational purposes only, and is not a substitute for qualified, individualized medical advice. You should discuss your potential elective procedure with your own doctor(s), including your primary care physician and the doctor who will perform your procedure if you decide to proceed.
How it’s done
Some centers make a distinction between preimplantation genetic screening (PGS), in which embryos from healthy parents with no known genetic disease are screened for potential problems, and preimplantation genetic diagnosis (PGD), in which embryos from parents with a known genetic disease in the family are checked for that disease. Other centers call both of these activities PGD, or both PGS. For the purposes of this article, the screening of embryos from parents with and without known genetic diseases will be referred to as PGD, since the process of screening is the same in either case.
PGD is performed during the embryo incubation part of the IVF procedure. (For more information about the various steps of the IVF procedure, which is complex, please visit our page called In Vitro Fertilization (IVF): the Procedure and Recovery.) When eggs and sperm are mixed, embryos are generally created within a few hours (if intracytoplasmic sperm injection, or ICSI, is used, then embryos are created at the time of that procedure). The embryos are then incubated for several days. After 3-4 days, the embryos have enough cells to allow for PGD. One or two cells is carefully removed from each embryo. Because the cells at this early stage are still pluripotent, meaning that they can develop into any kind of cell in the body, removing one or two cells from the embryo does not damage it or affect its ability to develop into a baby.
The cells then undergo genetic testing. This testing can detect major chromosomal abnormalities; some such abnormalities, such as Down’s syndrome, could result in a baby with health problems, while most of them render the embryo incapable of developing into a baby at all. The testing can also detect certain genetic diseases, such as cystic fibrosis or Tay-Sachs disease. The embryo can be screened for a panel of the most common genetic diseases; if the parents have a particular genetic disease in the family that is not included in that panel, the embryo will also be tested for that specific disease.
After the testing, the embryos that have chromosomal abnormalities are discarded. If there are several healthy embryos remaining, only one or a few may be selected for transfer; the remaining embryos may be stored for potential use in future IVF cycles, if the intended parents so choose.
Preparing for the procedure
Choosing your clinic
When choosing an assisted reproductive technology clinic (sometimes called a fertility clinic), there are several factors you may want to take into consideration. One is the physician(s) and others who will oversee your care. Make sure that your physician is board-certified; you may want to know that a board-certified reproductive endocrinologist (a specialist in the hormones involved in reproduction) is on the staff, as a consultant if necessary. You should also expect that your clinic will be a member of the Society for Assisted Reproductive Technology (SART), and follows the guidelines of the American Society for Reproductive Medicine (ASRM). You might also want to consider the clinic’s success rates, which are collected and published by the Centers for Disease Control (CDC), but you should be aware that interpreting this data is more complicated than you might think.
For more help in your search for a reproductive medicine specialist, visit our How to Find the Best Assisted Reproductive Technology Clinic page. At Doctor Review, you can also search providers for patient reviews to help you find the very best.
Getting ready for the procedure
Before going through IVF with or without PGD, both the man and the woman will have several diagnostic procedures, blood tests, and examinations. In some cases, other types of infertility treatment, such as ovulation induction (stand-alone; this is also part of IVF) or intrauterine insemination, may be done first, and IVF will only be necessary if these are unsuccessful. Each time that embryos are created for IVF, the parents can choose whether or not to use PGD.
The recovery from a cycle of IVF that uses PGD is the same as for a non-PGD cycle. See the IVF page for more details.