Three simple metrics to define in vitro fertilization success rates.

Describing clinical outcomes from assisted reproduction technology (ART) treatment cycles has been an evolving challenge throughout the world. Three simple metrics provide a transparent and highly accurate summary of ART outcomes. The first metric is the probability of having no embryos available to transfer. This metric incorporates all causes of failure from initiation of the treatment cycle up to the point immediately before actual embryo transfer. Patients will know what the risk is of failing, whether it is due to poor follicular stimulation, failed fertilization, poor embryo development, or abnormal preimplantation genetic testing for aneuploidy (PGT-A) results. The second and most important metric is sustained implantation rate: the probability that any transferred embryo will implant and progress to delivery. In the event of a single-embryo transfer, the metric is identical to delivery rate per transfer. By calculating per embryo, it provides a summary of the quality of outcomes within the program without the obscuring effect of multiple-embryo transfer. The final metric is the number of supernumerary embryos cryopreserved during the cycle. This speaks to the efficiency of the process by providing an estimate of potential benefits which may come from an additional transfer should the first one be unsuccessful or even to allow the couple to pursue an additional child without another full ART cycle. These metrics are easy to calculate and provide a detailed picture of the outcomes attained by the program.