PGT-M and PGT-A are laboratory techniques that evaluate embryos before the embryo transfer
Both PGT-M and PGT-A occur during an IVF cycle. IVF embryos can undergo testing for chromosomal abnormalities or genetic diseases prior to embryo transfer. Doing so can decrease the chance of IVF cycle failure, miscarriage and birth defects. These techniques can assist in the selection of the embryo that is most likely going to result in a pregnancy and a healthy baby.
Embryo testing often occurs at the blastocyst stage (Day 5 of development) via trophectoderm biopsy (biopsy of placental cells). Day 5 embryo testing means that the embryos must be frozen immediately. Upon receiving the results, we will thaw the embryos and transfer a healthy one to the uterus.
Preimplantation Genetic Testing for Monogenic Disorders (PGT-M)
Formerly called PGD, PGT-M involves testing the embryos for specific diseases, such as cystic fibrosis, beta thalassemia and retinoblastoma. It can identify sex-linked diseases such as hemophilia. Testing can also occur for human leukocyte antigen (HLA) matching and chromosomal translocations. Embryos can undergo screening for mutations that increase the chance of disease, like the cancer predisposition mutation BRCA1. Most diseases and disorders that are the result of a genetic mutation can be tested for via PGT-M. Depending on the mutation, laboratory professionals can either use an existing protocol or develop a new one to identify the embryos that carry that specific mutation.
Preimplantation Genetic Testing for Aneuploidy (PGT-A)
Women over 35 or women with a history of recurrent miscarriage may be more likely to have embryos that are chromosomally abnormal. PGT-A, formerly PGS, can identify those embryos that have a gain or loss of genetic material (aneuploidy). Aneuploid embryos will most often not implant in the uterus after transfer (leading to a negative pregnancy test). However, they are the most common cause of miscarriages in the first trimester and can sometimes lead to the birth of a child with severe health issues. Like PGT-M, PGT-A also occurs on Day 5 of development. Therefore, the embryos are frozen and placed back in the uterus in a subsequent cycle. The screening is performed with technology that allows for testing of all 23 pairs of chromosomes.