Rescue ICSI Improved Cumulative Live Birth Rate for Cycles with Second Polar Body Extrusion Rate <50% in Young Women: Generalized Addictive Model

To determine the indications for early rescue intracytoplasmic sperm injection (ICSI) application. A retrospective cohort study SUBJECTS: The study included 19,808 patients who underwent conventional in vitro fertilization (IVF) or rescue ICSI for their first cycles between February 2017 and December 2021. Rescue ICSI cycles constituted the study group, where oocytes that had not extruded the second polar body 4-6 hours after insemination were rescued by ICSI. The control group consisted of conventional IVF cycles with no interventions to rescue oocytes without the second polar body. Generalized additive models (GAMs) were constructed to describe the relationship between the second polar body extrusion rate and cumulative live birth rate in conventional IVF and rescue ICSI cycles, respectively. The cutoff value of the second polar body extrusion rate guiding rescue ICSI application was determined from the intersection point of GAMs. Maternal age range applicable to rescue ICSI was further analyzed using the same method. Clinical outcomes were compared between conventional IVF and rescue ICSI cycles across different second polar body extrusion rate and maternal age subgroups. The second polar body extrusion rate and maternal age range for rescue ICSI application, normal fertilization rate, and cumulative live birth rate. GAMs showed that the cutoff value for the second polar body extrusion rate about rescue ICSI application was 50%. When the rate