Received September 25, 2023
Accepted March 20, 2024

Background: Late follicular premature progesterone rise is a complex phenomenon encountered during assisted reproductive technologies (ART) treatments; different etiologies can occur in the same patient. Low ovarian responders may be the best example since higher FSH doses and ovarian ageing-related changes may interact and generate a premature progesterone rise.  Objectives: This study aims to explore the correlation between progesterone levels on hCG day and the progesterone-to-follicle index and compare the progesterone-to-follicle index according to ovarian response.  Materials and Methods: We performed a retrospective, observational, analytic, cross-sectional, and cohort study at the Reproductive Endocrinology Department at Centro Médico Nacional 20 de Noviembre between January 2015 and January 2020. After verifying for normalcy, a Spearman Rho, Principal Component Analysis, and a simple linear regression model were performed. Treatment cycles were classified according to their ovarian response. Low-ovarian responders were classified according to Bologna Criteria. Then, an ANOVA test was performed to compare each group. Results: Our results show that the progesterone-to-follicle index correlates best with progesterone levels on hCG day. Comparing all the ovarian responses, low ovarian responders have the highest progesterone-to-follicle index of the four groups.  Conclusions: Low ovarian responders produce more progesterone per follicle than regular and high responders.