RESUMEN
OBJECTIVE: The aim of this study was to investigate the impact of pretreatment with transdermal estradiol (E₂) compared to oral contraceptive pills (OCPs) on controlled ovarian stimulation (COS) response in normal responders undergoing fresh in vitro fertilization (IVF)-embryo transfer (ET) cycles. METHODS: A retrospective cohort study was performed of normal responders undergoing fresh IVF-ET cycles who received pretreatment with transdermal E₂ versus OCPs prior to fresh IVF-ET. The total days of ovarian stimulation, total dosage of gonadotropins, total number of oocytes, and mature oocytes retrieved were noted. Pregnancy outcomes after ET were also recorded. RESULTS: A total of 2,092 patients met the inclusion criteria: 1,057 and 1,035 patients in the transdermal E₂ and OCP groups, respectively. Patients in the OCP group had a longer duration of COS (10.7±1.63 days, p<0.01) than the E₂ group (9.92±1.94 days). Patients in the OCP group also required higher cumulative doses of gonadotropins (2,657.3±1,187.9 IU) than those in the E₂ group (2,550.1±1,270.2 IU, p=0.002). No statistically significant differences were found in the total and mature oocytes retrieved or in the rates of biochemical pregnancy, clinical pregnancy, spontaneous miscarriage, and live birth between the groups. CONCLUSION: Our findings suggest that compared to OCPs, pretreatment with transdermal E₂ is associated with a shorter duration of ovarian stimulation and lower gonadotropin utilization, without compromising the oocyte yield or pregnancy outcomes in normal-responder patients undergoing fresh IVF.