Overview Fixed Versus Flexible Gonadotropin-releasing Hormone (GnRH) Antagonist Initiation Status: Completed Trial end date: 2008-03-01 Target enrollment: Participant gender: Summary This is a comparison of pregnancy achievement between two GnRH antagonist protocols which differ in the timing of GnRH antagonist initiation. Phase: Phase 4 Details Lead Sponsor: Aristotle University Of ThessalonikiTreatments: Cetrorelix