Aneuploidy Screening (PGS) and array-CGH

Using the techniques developed for PGD, preimplantation aneuploidy screening (PGS) was developed to try to help identify the ‘best’ embryo for transfer by examining the chromosomes from embryos for couples going through IVF.   The main indications for PGS have been advanced maternal age (over 40), repeated IVF failure, repeated miscarriage and severe male factor infertility.  Up until recently, the technique used was called FISH and it only looked at a few of the 23 pairs of chromosomes present in the embryo.  The majority of clinics were performing biopsy on day 3 of development, which may not be the optimum time to examine the chromosomes.  Data from eleven randomised controlled trials have shown that PGS did not improve delivery rates.

At the CRGH we biopsy embryos at either the cleavage (day 3) or blastocyst (day 5) stage and we are now using array-CGH (comparative genomic hybridization) technology that allows all of the chromosomes from the embryo to be analysed.  Joyce Harper has written a review on the use of arrays in PGD and PGS, which was published in Fertility and Sterility in 2010 - Click here to see.