How accurate is PGT-M?

PGT-M is highly accurate but not absolute, and your clinic should give you a specific figure for your own case. ESHRE recommends that the residual risk of misdiagnosis is established for each individual test set-up, and that this is stated in your work-up report along with the test limitations. That number is specific to your family and your condition, because it depends on the genetic markers available in your family and how close they sit to the gene in question. You should also be able to ask for the centre's overall misdiagnosis rate. ESHRE recommends published and in-house estimates be available on request to prospective patients, alongside pregnancy and live birth rates. Why misdiagnosis can happen, in plain terms: Sometimes only one copy of a gene amplifies in the test, and the other is missed — called allele drop-out. Genetic material can recombine between the marker and the gene, so the marker no longer reliably indicates the gene. Samples can be contaminated, or DNA damaged during biopsy. Strategies using many genetic markers across the genome generally carry lower residual risk than older approaches targeting a single region, because the effect of any one marker failing is diluted. Because a residual risk always remains, ESHRE recommends prenatal diagnosis is offered to all women who become pregnant following PGT. If you would rather not have an invasive test, cord blood testing after birth is an alternative — arrange it in advance.