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

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 18-36 years treated with either a single dose of corifollitropin alfa (756 women) or daily recombinant FSH (750 women) for the first 7 days 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 1 week of stimulation compared with women who required a longer duration of stimulation.