Ovulation induction with a starting dose of 50 IU of recombinant follicle stimulating hormone in WHO group II anovulatory women: the IO‐50 study, a prospective, observational, multicentre, open trial

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Abstract
Objective To assess the efficacy and safety in clinical practice of a low dose regimen of 50 IU of recombinant follicle stimulating hormone in induction of ovulation. Design Prospective, observational, non‐comparative, open, multicentre study. Setting Eighty‐eight infertility clinics and teaching hospital fertility units throughout Spain. Population Women with normogonadotrophic chronic anovulation (WHO group II) with or without echographic diagnosis of polycystic ovary syndrome. Methods Low dose step‐up protocol of recombinant follicle stimulating hormone administration (follitropin beta, Puregon) with a starting dose of 50 IU and weekly increments according to follicular response monitored prospectively by transvaginal ultrasonography. Patients were followed for a minimum of one cycle and a maximum of six. Main outcome measures Rate and size of follicular growth, cumulative ovulation rate, follicle stimulating hormone doses and duration of treatment, pregnancy and cycle cancellation rate, ovarian hyperstimulation syndrome and multiple pregnancy. Results A total of 945 treatment cycles were evaluated. In 817 cycles, ovulation was induced with human chorionic gonadotrophin (hCG) and in 501 (61.3%) unifollicular development (a follicle of ≥18 mm) was achieved. A total of 128 cycles (13.5%) were cancelled because of ovarian hyper‐responsiveness or spontaneous ovulation. The cumulative ovulation rate (confirmed by mid‐luteal serum progesterone concentrations) after six treatment cycles was 84%. There were 136 clinical pregnancies (14.4% pregnancies per cycle). The cumulative pregnancy rate after six treatment cycles was 53.1%. Eight twin pregnancies occurred. Thirteen women miscarried and there were two cases of ectopic pregnancies. The median of average daily doses of follitropin beta in all cycles was 50 IU. Between 68% and 86% of patients received treatment with follitropin beta for a maximum of 14 days. Ovarian hyperstimulation syndrome occurred in 64 (6.8%) cases but no case of severe ovarian hyperstimulation developed. Conclusions Low dose regimen of 50 IU of recombinant follicle stimulating hormone (Puregon) is efficient, safe and well tolerated for inducing follicular development in WHO group II anovulatory women.

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