Preimplantation Genetic Screening (PGS) for Aneuploidy

Preimplantation Genetic Screening (PGS) for Aneuploidy: improved pregnancy rates in advanced maternal age, recurrent miscarriage and repeated IVF failure

Preimplantation genetic screening (PGS) for aneuploidy, or simply, aneuploidy screening, uses the same approach as PGD to identify embryos with abnormal numbers of chromosomes. Many of these embryos are not viable and will either fail to implant, cause miscarriage or rarely result in fetal or congenital abnormalities. Unfortunately, as aneuploid embryos initially develop normally and cannot be distinguished on the basis of their appearance, they are equally likely to be selected for transfer following IVF. There is now growing evidence in patients at high risk that identifying aneuploid embryos by PGS and transferring only embryos with the normal number of the chromosomes analysed improves pregnancy rates, reduces miscarriage rates and reduces the chance of congenital abnormalities associated with aneuploidy. Infertile patients who can benefit from aneuploidy screening include those in which the female partner is of advanced maternal age, couples having recurrent miscarriage (not caused by chromosomal abnormality in the parents) and couples with recurrent IVF failure.

FISHing for chromosomes
The nucleus of a single cell removed from an early human embryo Fluorescence in situ hybridisation (FISH) with a mix of chromosome specific probes for chromosomes X (green) Y (red) and 18 (blue).