How does PGT-A work?

The sequence, step by step: IVF, with eggs collected and fertilised as usual. Embryos are cultured to day 5 or 6, when they reach blastocyst stage. Not all embryos reach this point. A few cells — typically around five — are removed from the trophectoderm, the outer layer that becomes the placenta. The inner cell mass that becomes the baby is not sampled. The embryo is frozen while testing proceeds. The cells are analysed, usually by next-generation sequencing, to count chromosomes. Results return, generally within one to two weeks. Ask your clinic for their turnaround. An embryo is selected and transferred in a later frozen cycle. Two implications of this process worth understanding: Because the tested cells come from the placental lineage rather than the baby, results usually but not always reflect the embryo. This is the source of most of PGT-A's limitations. Because testing requires blastocyst culture, freezing and a later transfer, PGT-A changes the shape of your treatment. There is no fresh transfer in the same cycle. If few embryos reach blastocyst, few or none may be available to test. ESHRE notes there is no indication that embryo biopsy causes an increased risk of adverse neonatal outcome. A small number of embryos may not survive biopsy and freezing — ask your clinic for their own figures. Ask what happens if no embryo passes testing, and what that would cost you.