Two-year experience of Double-Factor Preimplantation Genetic Diagnosis: preliminary results

Preimplantation Genetic Diagnosis (PGD) was first employed successfully for a monogenic disease detection almost 20 years ago (Handyside et al., 1990). PGD was also applied to screen for chromosomal abnormalities in couples at risk of aneuploidy (i.e., Preimplantation Genetic Screening: PGS) six years later (Munne and Weier, 1996, Verlinsky et al., 1996, Verlinsky et al., 1996). Currently, both approaches have been extensively used worldwide with more than 2,000 scientific publications. Briefly, PGS aims for the selection of euploid embryos to transfer, aiming to increase their implantation rate. FISH for 9 chromosomes is mostly the technique applied in PGS. It seems, however, that according to recent publications PGS may not be useful (Staessen et al., 2004, Staessen et al., 2008, Hardarson et al., 2008, Mastenbroek et al., 2007). In fact, analyzing the latest data presented by the European Society of Human Reproduction and Embryology (E.S.R.H.E.), on average just 27.4% of the transferred PGS-selected embryos implant (3,926 positive heartbeats / 14,325 transferred embryos)( Harper et al., 2010). On the other hand, after 167,192 ART cycles in Europe using ICSI, the pregnancy rate is 29.8% (Andersen et al., 2008). Obviously, PGS patients differ from ICSI patients since the first ones suffer from repetitive implantation failure (RIF) or have an advanced maternal age (AMA), but the low implantation rate obtained in these patients still remains as a problematic issue. But, also referring to the E.S.H.R.E. data, the implantation rate in patients undergoing PGD for a monogenic disease, in which the maternal age is not at risk of producing aneuploid