Preimplantation Genetic Screening (PGS) is a method of screening abnormal chromosomes on the embryo before they are transferred to the uterus for fertilization. It is often done in a lab using in vitro fertilization (IVF).
Unlike Preimplantation Genetic Diagnosis (PGD) which is done when one or both parents have a known genetic abnormality, preimplantation genetic screening involves testing the embryos from presumed chromosomally normal genetic parents to determine aneuploidy.
Preimplantation genetic screening (PGS) is of the utmost importance because many embryos with chromosomal abnormalities hardly result in pregnancies. Besides, even when an embryo with an abnormal chromosome results in pregnancy, it can easily end in a miscarriage. The whole essence of this type of screening is therefore to make it possible for women to get pregnant through IVF and have healthy children with low risks of genetic disorders such as Down Syndrome. Of course, this test also looks out for those other abnormal chromosomes called translocations, that can cause growth or certain organ dysfunctions in children.
For the screening to be effective, one or more cells from each embryo are sent to the lab for testing. The unhealthy embryos are often discarded whereas the genetically healthy ones are transferred to the uterus for a possibility to attach to the lining and produce a pregnancy.
It is apparent that all women have some eggs that are chromosomally abnormal, just like all men have some sperms that are also chromosomally abnormal. The percentage of embryos that are abnormal can be further affected by many other factors, like age and the health history of the parents. Therefore, to ensure that healthy children are born, preimplantation genetic screening is recommended for parents opting for IVF.
Preimplantation genetic screening is particularly recommended for anyone who has or is a carrier of a known genetic disorder. However, it is also recommended for women with recurrent miscarriages, multiple failed fertility treatments and for older women whose ovaries do not work as expected.