The Evolution of Success Metrics in Assisted Reproduction
For decades, the primary benchmark of success in in vitro fertilization (IVF) was the live birth rate (LBR) per fresh embryo transfer. This metric, while useful, often failed to account for the total reproductive potential of a single ovarian stimulation cycle. With the advent of vitrification and the increasing shift toward frozen embryo transfers, the medical community has pivoted toward the cumulative live birth rate (CLBR) as the most comprehensive measure of clinical efficacy. CLBR includes births from both the fresh transfer and all subsequent frozen-thawed transfers derived from a single egg retrieval.
A central question for clinicians remains: what is the optimal number of oocytes to retrieve? While higher yields generally provide more embryos, they also raise concerns about ovarian hyperstimulation syndrome (OHSS) and potential declines in egg quality or endometrial receptivity. A new pooled analysis of four randomized controlled trials (RCTs) provides critical data on this relationship, specifically in the context of ovarian stimulation with follitropin delta.
