Short follicular phase of stimulation following corifollitropin alfa or daily recombinant FSH treatment does not compromise clinical outcome: a retrospective analysis of the Engage trial

Abstract

To evaluate whether a short follicular phase of ovarian stimulation compromises the chance of pregnancy, subjects from a double-blind, randomized trial treated with a single dose of corifollitropin alfa (n=756) or daily recombinant FSH (n=750) were categorized as early responders if three follicles ⩾17mm were reached and human chorionic gonadotrophin (HCG) was administered prior to or on stimulation day 8, and as normal responders if three follicles ⩾17mm were reached and HCG was administered after stimulation day 8. In the corifollitropin alfa and recombinant FSH groups, 23.2% and 29.1%, respectively, were early responders (P=0.01). Regardless of the treatment group, the initial ovarian response was higher in early responders, but with two extra days of stimulation, the number and size of follicles on the day of HCG in the normal responders was similar to those of the early responders. The number of oocytes was similar in both response groups following corifollitropin alfa treatment (13.6 versus 14.5) and recombinant FSH treatment (12.8, both groups). The ongoing pregnancy rates were comparable for early and normal responders regardless of the treatment group, supporting successful outcome following a stimulation period of only 1week.During ovarian stimulation for assisted reproduction, some women respond earlier than others to treatment with follicle-stimulating agents and require fewer days of treatment. To evaluate whether such short stimulation jeopardizes the chance of pregnancy, clinical outcomes of early responders and normal responders were compared in women aged 18–36years treated with either a single dose of corifollitropin alfa (756 women) or daily recombinant FSH (750 women) for the first 7days of stimulation. On average, about 25% of the evaluated women were early responders. The initial ovarian response was higher in early responders than in normal responders but the number of eggs retrieved and the ongoing pregnancy rates in early and normal responders were similar regardless of the treatment group. This study shows that the chance of ongoing pregnancy was not compromised in women requiring only 1week of stimulation compared with women who required a longer duration of stimulation.