Therefore, it seems clear that the search for developing mono or bifollicular cycles is important in ovarian induction cycles, for the purpose of preventing the above mentioned multiple pregnancy problems and the risk of OHSS. The intent of this study was to figure out the real mono-bifollicular development rate that is obtained under normal care conditions following OI treatment with follitropin alpha filled by mass prescribed in accordance with standard practice. Therefore, a measure of the efficiency of the product for achieving the development of one or two follicles. Data was collected from 56 centres of the Autonomous Communities that accepted this observational study, until achieving a total of 410 ovulation induction cycles.