What is PGT-SR?

PGT-SR — preimplantation genetic testing for structural rearrangements — tests embryos when one partner carries a chromosome rearrangement such as a balanced translocation or inversion. A carrier is healthy, because all the genetic material is present, just arranged differently. The difficulty arises when eggs or sperm are formed: the rearranged chromosomes can segregate in ways that leave an embryo with too much or too little material. Those embryos usually do not implant or miscarry early, which is why translocations often present as recurrent pregnancy loss rather than as a health problem in the carrier. PGT-SR identifies embryos with a balanced chromosome complement so those can be transferred. Two technical points worth knowing: Most methods cannot distinguish an embryo that is completely normal from one that is a balanced carrier like you. Both are healthy and transferable, but you may not be told which is which. Testing cannot detect uniparental disomy, where both copies of a chromosome come from one parent, which is a recognised additional consideration for some translocations. Before committing, ask about the numbers. A balanced translocation substantially reduces the proportion of transferable embryos — one study found couples needed on average at least 4.5 blastocysts for a good chance of one transferable embryo. Several retrieval cycles may be needed, particularly with reduced ovarian reserve. And ask specifically about natural conception outcomes, which are better than most couples are told.