Differences in Follicle Development and Hormone Dynamics Between Controlled Ovarian Stimulation (COS) Using Follitropin Delta and that Using Follitropin Alfa

Abstract

Background: We compared the performance of follitropin delta and follitropin alfa in the gonadotropin-releasing hormone (GnRH) antagonist protocol for controlled ovarian stimulation (COS) and discussed the distinctive features of follitropin delta in COS. Methods: Patients underwent COS using the GnRH antagonist protocol with either recombinant follicle-stimulating hormone (FSH) and oocytes were retrieved. We compared the results of COS, oocyte pick up, fertilization, embryo culture, and clinical pregnancy between the follitropin alfa group and the follitropin delta group. Results: The serum estrogen level at trigger was significantly lower in the delta than in the alfa group (3,576.69 ± 1,775.60 vs. 2,833.19 ± 1,567.88) as was serum P4 level (2.14 ± 1.26 vs. 1.19 ± 0.85). The stimulation duration (in days) were longer (12.97 ± 2.38 vs. 13.96 ± 2.26) and total gonadotropin dose significantly lower (199.69 ± 54.47 vs. 114.27 ± 39.92), respectively, in the delta group than in the alfa group. The ovarian hyperstimulation syndrome (OHSS) rate was significantly lower in the delta than in the alfa group (48.1% vs. 58.6%). Fertilization, good blastocyst, and clinical pregnancy rates were not significantly different. COS using follitropin delta is characterized by significantly slower follicle development than COS using follitropin alfa. A comparison of developing follicles showed that the minimum follicle was significantly smaller in the delta group on days 6–8 of COS. The maximum follicle was significantly smaller in the delta group on days 6–8 and 11–13 of COS. The number of follicles larger than 14 mm was significantly lower in the delta group on days 6–8 of COS. Conclusions: Using follitropin delta is associated with slow follicular development, slow serum E2 elevation, and longer stimulation duration; however, excessive elevation of serum estrogen levels during COS is reduced and so is the incidence of mild OHSS.