Objective: To assess the effect of different starting follitropin’s beta dose (50 IU, 75 IU and 100 IU daily) for ovulation induction combined with intrauterine insemination on mono-follicular development. Subject: Prospective study. Setting: Centre for Assisted Reproduction SANUS, Pardubice. Subject and method: From March 2005 to November 2007 we performed a total number of 111 ovarian stimulations for patients with unexplained infertility, anovulatory disorder or mild male factor. We divided patients into groups based on patient’s response to clomifen citrate treatment. We examined follicular growth day 9 by transvaginal ultrasound and if necessary we adjusted gonadotropins’s dose. Results: We performed 104 intrauterine inseminations (94% of cycles with ovulation induction). We proved mono-follicular development in 36%, 37% and 36% (ns), number of follicles 1,9 ± 0,8, 2,2 ± 1,2 and 2,5 ± 1,8 (ns), endometrial thickness (mm) 8,5 ± 1,2, 8,6 ± 1,7 and 9,1 ± 1,8 (ns), total dose of rFSH (IU) 440 ± 156, 583 ± 154 and 830 ± 268 (p<0.001) in 50 IU, 75 IU and 100 IU follitropin’s beta groups. We achieved a total of 18 pregnancies (pregnancy rate 17%). Conclusions: 50 IU follitropin beta daily offers 36% probability of mono-follicular development. The disadvantage may be an increased risk of cycle cancellation due to low ovarian response. Daily doses 75 IU or 100 IU increase total consumption of rFSH.

        Key words: ovulation induction, intrauterine insemination, clomifene citrate, gonadotropins, follitropin beta, pregnancy rate, OHSS