PGT-A, Preimplantation Genetic Testing for Aneuploidy
What is PGT-A?
PGT-A or Preimplantation Genetic Testing for Aneuploidy is proven to be effective at identifying chromosomally normal (euploid) and chromosomally abnormal (aneuploid) embryos. It is an accurate, safe, and cost-effective genetics screening service that helps fertility clinics improve the implantation rate for their patients’ success rate for a healthy pregnancy.
What’s involved in PGT-A Screening?
Though a quick, non-invasive biopsy of trophectoderm (TE) cells of a day 5 blastocyst, we are able to ensure the exact number and DNA content of each chromosome within each embryo sample. Only TE cells are needed for the biopsy. They are the outer cells that grow to be the placenta. The inner mass cells that grow to become the fetus are NOT biopsied for PGT-A.
Step 1: In vitro fertilization [introduction of the sperm and egg] occurs in your fertility clinic’s embryology lab and is monitored for viable embryonic development.
Step 2: The viable embryo blastocyst’s TE cells are biopsied on DAY 5 by your clinic’s embryology team and the blastocyst is cryopreserved. The biopsied TE cells are sent to our genomics lab for PGT-A screening.
Step 3: We screen the biopsied TE cells and report the findings to your clinic, identifying any euploid, euploid mosaic and/or aneuploid embryos.
Step 4: Embryo selection with your physician. On discussing the embryo selection for transfer with your physician, the PGT-A findings, along with zygote scoring and the morphology of the embryo should all be combined to inform your discussion. (You may wish to speak with a genetic counsellor about the results, particularly if mosaicism is involved.)
Step 5: The healthy embryos are thawed and transferred (healthy embryos not transferred can be frozen for future use).
Is PGT-A right for me?
PGT-A can help all women increase their chance of pregnancy, however it’s particularly relevant to women with:
- advance reproductive age (>35yrs)
- experience of several unsuccessful IVF cycles
- history of repeated miscarriage
- known history of chromosomal abnormality in both or either parent or in a previous pregnancy
PGT-A significantly increased chances of pregnancy
PGT-A is unanimously recommended by Canadian and International regulating bodies
The Preimplantation Genetic Diagnosis International Society (PGDIS) states that “Indeed, using these methods (preimplantation genetic diagnosis for aneuploidy, PGD-A, or preimplantation genetic screening, PGS) has now been shown in numerous studies to improve implantation, pregnancy and live birth rates (per embryo transferred) and reduce miscarriage rates.”
PGDIS Newsletter, July 19, 2016 – PGDIS Position Statement on Chromosome Mosaicism and Preimplantation Aneuploidy Testing at the blastocyst stage.”
The Society of Obstetricians and Gynaecologists of Canada (SOGC) states that “Preimplantation genetic screening […] increases implantation rates and improves embryo selection in IVF cycles in patients ‘with a good prognosis’.”
(Dahdouh et al., (2015) J. Obstet. Gynaecol. Can., 37(5):451-463).
A recent study on obstetrical and neonatal outcomes published by the American Journal of Obstetrics & Gynaecology (AJOG) states “By culturing embryos to the blastocyst stage, performing a trophectoderm biopsy, and amplifying DNA with qPCR assays on each chromosome, a single euploid blastocyst with high reproductive potential can be selected for transfer. This paradigm eliminates the risk of multizygotic multiple gestation and increases the chance for a healthy, term singleton delivery without requiring patients to undergo an increased number of failed cycles. The improved obstetrical and neonatal outcomes suggest this approach may become the standard of care for infertile couples requiring IVF.”
Eric J. Forman et al., February 2014, American Journal of Obstetrics & Gynecology, 157.e6
“A study performed at Reproductive Medicine Associates
of New Jersey demonstrated that TE biopsy is safer than biopsying a single cell on day 3, and it’s also more accurate. A separate collection of cells called the inner cell mass (ICM) becomes the actual embryo, and ultimately the baby, and is not touched by the embryologist when TE biopsy is performed.”
Eric Forman, MD, The Problem of Mosaic Embyros in IVF, https://www.fertilityiq.com/pgs- and-ccs-genetic-testing/the-problem-of-mosaic-embryos-in-ivf