Optimizing FSH Concentration Modulation in the Short-Acting GnRH-a Long Protocol for IVF/ICSI: A Retrospective Study

Introduction: Exogenous gonadotropin (Gn) is given to regulate follicle-stimulating hormone (FSH) levels to achieve optimal ovarian response in in vitro fertilization/intracytoplasmic sperm injection (IVF/ICSI). The objective of this study was to analyze the optimal degree of change in FSH blood concentration with ovarian responsiveness in a short-acting gonadotropin-releasing hormone agonist (GnRH-a) long protocol for IVF/ICSI. Methods: This retrospective study was conducted at Changzhou Maternity and Child Health Hospital's Reproductive Center from May 2017 to May 2023. A total of 794 ovarian stimulation cycles for IVF/ICSI using the short-acting GnRH-a long protocol was included. Ovarian responsiveness was assessed based on the number of follicles > 14 mm on human chorionic gonadotropin (HCG) trigger day, refine-follicular output rate (Refine-FORT) and good quality embryos. Delta 1 referred to the change in FSH level between days 6-8 of gonadotropin usage and baseline FSH, while Delta 2 referred to the change in FSH level between HCG trigger day and days 6-8 of gonadotropin usage. Simple and multiple linear regression analysis were performed to adjust for confounding factors. Results: The number of follicles > 14 mm on HCG trigger day was found to be the most suitable indicator for evaluating ovarian responsiveness compared to the number of follicles > 16 mm and the number of retrieved oocytes. When Delta 1 ranged from 1.94 to 3.37, the number of follicles > 14 mm on HCG trigger day was the highest. When Delta 1 ranged from 3.37 to 5.90, the Refine-FORT was the highest. However, when Delta 1 exceeded 5.90, the number of follicles > 14 mm on HCG trigger day, Refine-FORT and good quality embryo all significantly decreased. On the other hand, when Delta 2 was <= - 1.58, the number of follicles > 14 mm on HCG trigger day and the Refine-FORT were both the highest. Conclusion: This study identifies optimal Delta 1 and Delta 2 ranges for effective ovarian responsiveness in a short-acting GnRH-a long protocol for IVF/ICSI and introduces the novel measure of the number of follicles > 14 mm on HCG trigger day. The optimal range for Delta 1 was 1.94 to 3.37, and Delta 2 should be < - 1.58 for achieving a higher number and quality of oocytes.