Aneuploidy screening for embryo selection has come a long way ever since it was initially proposed as a means to improve clinical outcomes for infertile patients. It is obvious from the published data that PGS approaches using FISH to screen blastomeres, PBs, or TE samples are hampered by numerous technical issues that potentially could lead to increased misdiagnosis risks. Although there is evidence that day 3 PGS with the use of FISH may be capable of reducing the incidence of spontaneous abortion and aneuploid pregnancy, most laboratories have been unable to achieve any enhancement of implantation or pregnancy rates for patients undergoing IVF. The deficiencies of the early PGS methods have led several research groups to develop alternative molecular cytogenetic methods, examining the entire chromosome complement of single cells. These methods have now been optimized and validated, and they are increasingly used in a clinical setting. Because cleavage-stage biopsy carries a risk of misdiagnosis due to mosaicism, many IVF clinics have chosen either to sample the oocyte, via PB biopsy, or embryos at the blastocyst stage, via TE biopsy. Several RCTs are underway, taking place both in the United States and Europe, and using PB or blastocyst biopsy in combination with comprehensive molecular cytogenetic methods for PGS. We hope the results obtained from these RCTs will clarify whether or not PGS can make a significant positive difference in clinical outcomes for couples who require IVF to establish a successful pregnancy and ultimately a healthy live birth.
Dagan Wells is funded by the NIHR Biomedical Research Centre Program.
Semin Reprod Med. 2012;30(4):289-301. © 2012 Thieme Medical Publishers