Related Experiment Video
Updated: Nov 7, 2025

Fertility Preservation Through Oocyte Vitrification: Clinical and Laboratory Perspectives
Published on: September 16, 2021
Fixed versus flexible antagonist protocol in women with predicted high ovarian response except PCOS: a randomized
Xiu Luo1,2,3, Li Pei2,3, Fujie Li1,2
1Chongqing Key Laboratory of Human embryo Engineering, Chongqing, China.
Background:
No previous study directly compares the fixed day-5 initiation versus the flexible initiation of GnRH antagonist administration in IVF/ICSI for those patients who are predicted as high ovarian responders without PCOS. To evaluate whether the number of oocytes retrieved is different by using the two GnRH antagonist protocols in Chinese women with predicted high ovarian response except PCOS.
Methods:
A randomized controlled trial of 201 infertile women with predicted high ovarian response except PCOS undergoing in vitro fertilization. Ovary stimulation was performed using recombinant FSH and GnRH antagonists. GnRH antagonist ganirelix (0.25 mg/d) was started either on day 5 of stimulation (fixed group) or when LH was > 10 IU/L, and/or a follicle with mean diameter > 12 mm was present, and/or serum E2 was > 600 pg/ml. Patient monitoring was initiated on day 3 of stimulation in flexible group.
Result(S):
No significant difference was observed between the fixed and flexible groups regarding the number of oocytes retrieved (16.72 ± 7.25 vs. 17.47 ± 5.88, P = 0.421), the Gonadotropin treatment duration (9.53 ± 1.07 vs. 9.67 ± 1.03, P = 0.346) and total Gonadotropin dose (1427.75 ± 210.6 vs. 1455.94 ± 243.44, P = 0.381). GnRH antagonist treatment duration in fixed protocol was statistically longer than the flexible protocol (6.57 ± 1.17 vs 6.04 ± 1.03, P = 0.001). There was no premature LH surge in either protocol.
Conclusion(S):
Fixed GnRH antagonist administration on day 5 of stimulation appear to achieve a comparable oocyte retrieved compared with flexible antagonist administration.
Trial Registration:
NCT02635607 posted on December 16, 2015 in clinicaltrials.gov.
Related Concept Videos
Hormonal Control of the Ovarian Cycle
Before puberty, the hypothalamus releases GnRH in a low frequency, low amplitude pulsatile manner. This along with the immature hypothalamic-pituitary-gonadal axis activity, results in low estrogen levels and the absence of a fully functional ovarian cycle. At puberty, GnRH secretion increases in both frequency and...
Types of Biopharmaceutical Studies: Controlled and Non-Controlled Approaches
Non-controlled studies, commonly employed for initial exploration, lack a control group, rendering them susceptible to biases and external influences. In contrast,...
Bioequivalence Experimental Study Designs: Completely Randomized and Randomized Block Designs
Randomized Experiments
Simple randomization
Simple...
Bioavailability Study Design: Healthy Subjects Versus Patients

