Preimplantation Genetic Testing (PGT) with IVF Embryos can be tested for a serious genetic disorder using PGT-M, PGTSR, or they can be screened for the correct number of chromosomes using PGT-A. Only normal embryos are transferred.
Understanding the acronyms • PGT
Preimplantation Genetic Testing
• PGT – A: Preimplantation Genetic Testing – Aneuploidy • PGT – M: Preimplantation Genetic Testing – Monogenic Disorder • PGT – SR: Preimplantation Genetic Testing – Structural Rearrangement
Who can have PGT-M or PGT-SR?
Who can have PGT-A?
In New Zealand PGT is permitted for:
Anyone having IVF or ICSI can consider having PGT-A. It is possibe to do PGT-A at the same time as PGT-M or PGT-SR. PGT-A may be more suitable for:
• Serious conditions where a child has at least a 1 in 4 chance of inheriting the condition. • Chromosome abnormalities associated with recurrent miscarriage or advanced maternal age • Ethics Committee approval is required for other reasons, such as ‘saviour siblings’. PGT can’t be used for social reasons such as sex selection in New Zealand.
How does PGT work? People wanting PGT undergo IVF in the usual way. On day 3 of embryo development, a small hole is made in the soft shell of the embryo (called the ‘Zona Pellucida’) using a laser. Three or more cells are gently removed from each embryo, usually on day 5 (called ‘blastocyst biopsy’), and then the embryos are frozen. The cells are sent to a PGT laboratory for analysis. We commonly use Canterbury Health Laboratories in Christchurch or Monash IVF in Melbourne. The PGT lab tests the cells from each embryo and tells us which embryos are normal. Normal embryos can be thawed and transferred to the woman later.
Getting prepared for PGT-A The option of using PGT-A in IVF treatment is
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• People with many good quality embryos, to provide extra embryo selection •W omen aged 38 and older, because the chance of having the wrong number of chromosomes in an embryo increases from the age of 36.
discussed on page 73. You will need to decide whether to do PGT-A when you start your treatment cycle. If there is only one embryo suitable for PGT-A some people decide to have an embryo transfer instead of doing PGT-A, so we start luteal support to give this option. All PGT-A is privately funded. In addition to the standard consent form, there is a Fertility Associates consent form for PGT-A, and a consent form from the PGT lab too.
When is PGD-M or PGT-SR used? PGT-M is used to detect disorders caused by a change in a single gene (the M stands for monogenetic). Examples include Cystic Fibrosis (CF), Huntington’s Disease, Betathalassemia, Fragile X Syndrome (FXS) and Spinal Muscular Atrophy (SMA).
