When an embryo has more than, or fewer than, the normal number of chromosomes, that’s a condition known as aneuploidy. Embryos that are aneuploid may fail to implant in the uterus or may result in a miscarriage. Aneuploidy occurs across all age groups, but after a woman reaches age 35, the proportion of aneuploid embryos increases rapidly. Preimplantation genetic screening (PGS) is a way of identifying embryos with the correct number of chromosomes to improve your chances of a successful pregnancy. IVF pregnancy rates are significantly higher when PGS is used.