Received June 15, 2023
Accepted December 15, 2023

Research Question: Does progesterone levels on hCG day influence maturation rates and number of mature oocytes during ovarian stimulation for IVF/ICSI cycles? Design: A retrospective, observational, analytic, cross-sectional and cohort study was performed at the Reproductive Endocrinology Department of the Centro Médico Nacional 20 de Noviembre in Mexico City between 2015 to 2020. All female patients underwent an ovarian stimulation cycle for IVF/ICSI, either with a mild or conventional stimulation protocol. Patients were classified according to their progesterone levels, Group 1 <1.5ng/ml and Group 2 >1.5 mg/ml. A Spearman Rho test, a simple linear regression model, a Principal Component Analysis and a Student's T-test, were performed. Results: A total of 600 patients were included. The overall results showed that there is a positive correlation between the number of retrieved, mature oocytes and progesterone levels on HCG day. After the Principal Component Analysis we observed that poor ovarian responders had the lowest maturation rate and number of mature oocytes. While the Student’s t test showed that progesterone levels beyond 1.5 ng/ml are associated to a higher number of mature oocytes but not a better maturation rate. Conclusions: Higher serum progesterone levels are associated with increased retrieved and mature oocytes in high responders. At the same time, higher progesterone levels in lower responders are not associated with optimal ovarian response.