Impact of embryologist workload on ICSI fertilization rates

Introduction: Intracytoplasmic sperm injection (ICSI) is a widely used insemination method for fertilization of mature oocytes (MIIs) during IVF. Previous studies have sought to understand the factors that may influence ICSI success rates, such as sperm quality, oocyte quality, or embryologist training. Here, we aimed to explore whether embryologist workload, measured by number of ICSI procedures per day, number of MIIs per day, or number of MIIs per procedure, impacts ICSI success.

Methods: Historical, deidentified electronic medical record (EMR) data were collected from four IVF clinics in the U.S. We performed a retrospective analysis of 1,951 retrievals undergoing a total of 2,973 ICSI cycles between 2017 and 2021. Cycles using surgical sperm were excluded. ICSI fertilization rates were calculated as the number of fertilized oocytes (2PNs) divided by the number of MIIs. In cases where a patient’s cohort of MIIs were divided among multiple embryologists, fertilization rates were calculated for each procedure separately. Mean fertilization rates and 95% confidence intervals (CIs) were calculated for varying bin sizes.

Results: Daily workloads of 1-2, 3-5, and 6-10 procedures per embryologist resulted in mean fertilization rates and 95% CIs of 72.8% (71.0%, 74.6%), 72.4% (71.4%, 73.4%), and 74.4% (71.6%, 77.2%), respectively. Daily workloads of 1-6, 7-12, 13-20, 21-30, 31-40, 41-50, 50+ MIIs per embryologist resulted in mean fertilization rates and 95% CIs of 72.5% (68.6%, 76.4%), 71.3% (68.7%, 74.0%), 71.8% (70.1%, 73.6%), 73.8% (72.4%, 75.2%), 72.7% (70.8%, 74.6%), 77.2% (74.8%, 79.5%), and 74.6% (71.4%, 77.8%), respectively. Finally, ICSI procedures processing 1-6, 7-12, 13-20, and 21+ MIIs resulted in mean fertilization rates and 95% CIs of 71.7% (70.4%, 73.0%), 73.7% (72.6%, 74.9%), 75.5% (73.6%, 77.4%), and 75.0% (70.4%, 79.6%), respectively. Overall, our results suggest that busier workloads may result in slightly improved fertilization rates; however, for most bins, this was not statistically significant.

Conclusions: In this study, we investigated whether embryologist workload was a potential concern for ICSI procedures. Our results demonstrate that ICSI fertilization rates appear stable across the number of procedures per day, number of MIIs per day, and number of MIIs per procedure.