Highly significant improvement in embryo implantation and increased live birth rate achieved after comprehensive chromosomal screening: implications for single embryo transfer

Abstract

OBJECTIVE: To improve the identification of viable embryos for uterine transfer with a view to increasing implantation and birth rates. DESIGN: Prospective clinical trial. MATERIALS AND METHODS: Comparative genomic hybridization (CGH) was used to screen all 23 pairs of chromosomes for aneuploidy in over 500 blastocysts derived from 115 patients. The patients were of advanced maternal age (mean 39 years) and in most cases had at least one previous failed IVF attempt (mean failed cycles 2). RESULTS: The CGH approach underwent extensive validation prior to clinical application, confirming concordance between the biopsied trophectoderm (TE) cells and the inner cell mass. A full chromosome screen was obtained for 93% of blastocysts tested. Almost all patients (96%) had at least one normal embryo available for transfer. Currently, 42 patients have had their blastocysts transferred, with the remaining patients scheduled to receive transfers in the coming weeks. The clinical pregnancy rate stands at 86% (36/42). Fifteen cycles have now gone to term, giving a birth rate per cycle of 80% (versus 60% in control blastocyst transfer cycles). Even more impressive was the implantation rate (fetal heart detected) which was increased from 28% in controls to 66% (54/82) in cases with CGH screening (2.4 fold increase, P<0.0003). CONCLUSIONS: We report the first births following comprehensive chromosome screening of blastocyst stage embryos. The sampling of several TE cells led to a robust diagnosis, less susceptible to problems such as chromosomal mosaicism than previous screening methods. Implantation and birth rates were exceptional (66% per embryo and 80% per cycle started respectively). These results were especially good given the poor reproductive history of the patients and were significantly better than cycles without chromosome screening. The dramatic improvement in implantation rate provides a clear indication that methods such as this will allow high pregnancy and birth rates in cycles involving single embryo transfer.