Preimplantation genetic screening for aneuploidies(PGT-A)-
- PGS, preimplantation genetic screening, refers to removing one or more cells from an in vitro fertilization embryo to test for chromosomal normalcy. Embryos with a normal number of chromosomes can be transferred back to the uterus.
- PGS screens the embryo for normal chromosome number. There can be extra (trisomy) or missing (monosomy) chromosomes. Both conditions are a problem.
- Biopsy at the cleavage stage is done on day 3 of embryo development. At this point the embryo usually has 6 to 10 cells.
- The aim of PGS is to prevent recurrent miscarriages and to avoid having a child affected with the most common aneuploidy disorders – Down Syndrome (trisomy 21), Edwards Syndrome (trisomy 18), Patau Syndrome (trisomy 13), Turner syndrome (monosomy X), and Klinefelter syndrome (gonosomal trisomy XXY).
These trisomies originate from meiotic errors that may arise during the formation of gametes. - Indications-
- Couples with recurrent miscarriages
- Advanced maternal age-35 years and above
- Previous failed IVF’s-repeated implantation failures
- Low sperm counts-Male Infertility
- Benefits of Preimplantation Genetic Screening-
- Increases the chance of a healthy pregnancy across all age groups-The risk of having a pregnancy with a chromosome abnormality increases as females age.
- Reduces the likelihood of miscarriage- Embryos are chosen primarily on their visual quality –which cannot distinguish chromosomally normal embryos from abnormal ones. IVF cycles that do include PGS enable the identification of embryos with normal chromosomes, and are more likely to result in a pregnancy that leads to a healthy baby.
- Reduces time between IVF cycles-Preimplantation Genetic Screening reduces time between IVF cycles by allowing the identification of a normal embryo as soon as possible. If a woman goes through an IVF cycle and a normal embryo is not identified, she can start her next cycle right away.
- Allows for confident single-embryo transfer, which helps avoid the added health complications associated with twin or triplet pregnancies-PGS allows for single-embryo transfer by identifying the embryo that has the best chances of implanting and leading to a healthy child. Multiple pregnancies can cause increased risk for complications during pregnancy, such as preterm birth, abnormal placental function, preeclampsia, and others.