Abstract
Introduction: In an IVF cycle after ovulation stimulation, the goal is to prevent LH surge and wasting follicles. The use of GnRH antagonists to achieve this goal has been considered by infertility specialists in recent years. Two fixed or flexible drug regimens have been tested. The aim of this study was to compare the implications of induced pregnancy by two regimens with a flexible dose of GnRH antagonist and a half fixed dose of GnRH antagonist that was evaluated for the first time.
Materials and Methods: This randomized double-blinded controlled trial was conducted on 140 patients referring to the infertility department of Shariati Hospital between June 2017 and June 2018 who were candidates for IVF. Patients who were candidates for cyclic therapy with GnRH antagonists were randomly assigned (with a randomized table of numbers) to either the fixed dose group with a half dose of the GnRH antagonist (Group A, n = 70) or the flexible GnRH antagonist dose (Group B, n = 70).
Results: There was also difference in the numbers of IVF or IUI cycles across the two groups. The mean degree of the sperm motility and sperm morphology percentages were similar in the spouses of women in the two groups. With regard to the outcome of IVF, no difference was revealed in the mean number of mature follicles, number of retrieved oocytes, and number of transferred embryos (Table 3). The successful clinical pregnancy rate in the groups A and B was 20.0% and 18.6% respectively with no difference (p = 0.830). The successful clinical pregnancy rate in the groups A and B was 20.0% and 18.6% respectively with no difference (p = 0.830). Based on the multivariable logistic regression analysis, the fixed dose regimen with half dose of GnRH antagonist or GnRH flexible dose antagonist dose did not affect the IVF success. The final determinants of the success of IVF were the percentage of sperm morphology (OR = 1.237, P = 0.015) and BMI of the patients (OR = 0.836, P = 0.019).
Conclusion: Both GnRH antagonist regimens with flexible doses and the GnRH antagonist with a half fixed dose have similar effects on the outcome of IVF. Among the factors predicting the success rate of IVF, the role of reducing the morphology of sperm and obesity is very prominent.

Key words: IVF, GnRh antagonist, flexible dose, half dose, pregnancy.