What are aneuploid embryos?

An aneuploid embryo has an abnormal number of chromosomes — extra or missing material. Most do not implant, and those that do usually miscarry early. A few chromosome abnormalities are compatible with a live birth, including Down syndrome. Aneuploidy is common and largely age-related. Errors occur when eggs divide, and the frequency rises with age. It is not caused by anything you did, and it is not a sign of poor health in either partner. Most clinics do not transfer embryos reported as aneuploid, and that is standard practice. A few nuances worth understanding: The result comes from a few cells taken from the placental lineage. It usually reflects the embryo, but not always. There is a difference between a fully aneuploid result and a mosaic result, where only some tested cells were abnormal. Mosaic embryos are handled differently, and clinic policies vary. Laboratories differ in reporting thresholds, so an embryo classed one way at one laboratory might be classed differently at another. If all your embryos were reported aneuploid, that is a hard result. It does not mean the next cycle will be the same, and it is not a verdict on your ability to have a child. Ask your clinic what the pattern suggests and what your realistic prospects are. If you are being encouraged to transfer an embryo reported as fully aneuploid, ask for genetic counselling first — this is not standard practice and needs clear justification.