Importance of a 5- versus 7-day pill-free interval in a GnRH antagonist protocol using corifollitropin alfa: a prospective cohort study in oocyte donors

In this prospective cohort study, oocyte donors were recruited prospectively and assigned to receive corifollitropin alfa: 5 days after pill discontinuation (group D5; 42 donors), or 7 days after pill discontinuation (group D7; 50 donors) in a gonadotrophin-releasing hormone antagonist protocol. Fixed additional daily doses of 200 IU recombinent FSH (rFSH) were started after 7 days of corifollitropinalfa, until triggering. No significant differences in basal characteristics were observed between both groups. In group D5, mean (SD) total additional rFSH dose was 659 (452) IU; in group D7, total rFSH dose was 459 (356) IU (P = 0.022). Duration of stimulation was significantly longer in group D5 compared with group D7 (P = 0.002). No differences were found in total number of oocytes obtained. Total number of injections was significantly lower in group D7 compared with group D5 (9.8 [3.2] versus 11.9 [3.9], respectively; P = 0.004). Total cost of medication used for donor treatment was significantly higher in group D5 than in group D7 (P = 0.015). After more than 22 days of pill-taking, extending the pill-free interval to 7 days significantly reduces the total dose of gonadotrophins, duration of stimulation, total cost of medication and total number of injections.