How many embryos should be transferred? A validated score to predict ongoing implantation rate.

Objective: To developed a prognostic score to predict ongoing implantation rate according to clinical and biological parameters and to choose the number of embryos to be transferred in patients undergoing IVF/ICSI.

Study Design: The transfer score was established using multivariate analysis of biological and clinical parameters in 3211 fresh embryo transfers in a retrospective study. Then we validated the score in 694 fresh embryo transfers in a prospective study.