Received April 01, 2025
Accepted February 20, 2026

Background: Ovarian stimulation (OS) is a critical step in assisted reproductive techniques (ART); it has been routinely adopted since it substantially increases the whole process’s efficiency. Our study aims to compare the efficiency of mild OS with letrozole co-treatment vs conventional OS in expected low ovarian responders.  Materials and methods: A single-centre, observational, comparative, non-experimental and retrospective study using our database at the Reproductive Endocrinology Department at Centro Médico Nacional 20 de Noviembre in Mexico City was performed. Results: We compared the total rFSH dosage per oocyte, we noticed a statistically significant difference between groups, Group A 388.9 vs Group B 667.2 IU per retrieved oocyte (p<0.0002, 105 to 450 IU CI 95% ), Comparing total rFSH dosage per follicle, we noticed a statistically significant difference among Group A 397.5 vs Group B 590.2 IU per follicle (p <0.014, 39.2 to 346.2 IU, CI 95%) Conclusions: In expected poor ovarian responders, mild ovarian stimulation with letrozole co-treatment is much more efficient than conventional stimulation.