Your embryos can be tested for abnormal chromosomes before they are transferred to the uterus. Known as preimplantation genetic testing (PGT), one or more cells from each embryo are prepared (typically at day 5 of embryonic development) and sent to a lab for genetic testing. Since this testing takes time, your embryos will usually be frozen while waiting for the results. Then, based on the PGT results, genetically healthy embryos will be thawed and transferred to the patient’s uterus.
There are two different PGT procedures available. Preimplantation genetic diagnosis (PGD) involves testing the embryos for specific genetic disorders and is recommended for someone who is a carrier of a known genetic disorder. Preimplantation genetic screening (PGS) involves testing the embryos for chromosomal abnormalities by counting the number of chromosomes, and is recommended for someone with recurrent miscarriage, older (over the age of 35), or with multiple unexplained failed fertility treatments. Many embryos with chromosomal abnormalities will not result in a pregnancy or will end in miscarriage. PGS also identifies the sex of the embryos, giving the intended parents the ability to transfer embryos of a given sex. A disadvantage of PGT is that it often eliminates a large number of embryos, which means fewer embryos will be available for transfer. The percentage of embryos that are abnormal can be affected by many factors, including the age and health history of the parents. We recommend that you work with a genetic counselor if you choose PGT for your embryos.