In IVF, eggs are fertilized to create embryos, and then the embryos are incubated for several days. By this time, the embryos have several cells each. For PGS, one or two cells are removed (this does not harm the embryo). The DNA (genetic material) is extracted from the cell and then analyzed. PGS can look for chromosomal abnormalities (such as Down syndrome) or for the most common single-gene genetic diseases (such as Tay-Sachs disease and cystic fibrosis), and can also look for particular diseases that run in the family.
After the testing, the embryos that contain major genetic abnormalities or diseases are discarded. Of the remaining healthy embryos, one to four are transferred into the woman’s uterus (the number transferred depends on her medical history and age). If the healthy embryos are too numerous to transfer all at once, the couple may choose to freeze the extra embryos for potential use in future IVF cycles.
Why Choose PGS?
Couples may choose preimplantation genetic screening if the woman is over 34, which increases the risk of chromosomal abnormalities. Those who have experienced recurrent miscarriages, particularly early miscarriages, also may want to use PGS, because many chromosomal abnormalities lead to miscarriages (since the embryo is unable to develop into a viable baby). Similarly, those who’ve had trouble getting pregnant using fertility treatments may choose the testing. Parents who’ve previously conceived embryos with chromosomal abnormalities also may choose PGS.
Additionally, couples who have a family history of a single-gene genetic disease, or who are known to be carriers of one of these diseases, may want to use PGS. Some examples of genetic diseases in this category are cystic fibrosis, sickle cell disease, Huntington’s disease, and Duchenne muscular dystrophy. If there’s a genetic disease that runs in your family, and you aren’t sure whether it’s a single-gene disorder, a genetic counselor or your doctor can help you figure out whether or not PGS would be appropriate in your case.
Why is PGS Controversial?
Many couples turn to PGS if they have a genetic disease in the family, or if they’re suffering recurrent miscarriages. This can cause babies to be born who otherwise would never have been conceived, because the couple didn’t want to risk passing on the genetic disease.
However, many people also see the potential for abuse of this technology. Embryos could eventually be selected for qualities, such as intelligence or athletic ability, rather than simply eliminating diseases. Many people also see a connection between PGS and eugenics (which attempts to alter the genetics of the overall human population through eliminating those who aren’t perfect). Because millions of deaths and inconceivable suffering have occurred historically as a result of eugenics, many people are opposed to the use of PGS. Some are particularly uncomfortable with the discarding of the embryos that have the disease or chromosomal abnormality, because they see this as equivalent to killing a human being for having a problem.
You will have to evaluate for yourself how you feel about PGS, and whether you feel that its potential benefits outweigh its potential downsides. If you have questions or would like more information about PGS, please discuss this with us when you come for your next appointment at our fertility clinic near Chandler.