Research Question: Is there an association between the ovulation trigger dose of human chorionic gonadotrophin (HCG) and endogenous progesterone production during the luteal phase?
Design: This randomized controlled four-arm study, at the Fertility Clinic, Odense University Hospital, Denmark, included women undergoing gonadotrophin-releasing hormone (GnRH) antagonist IVF treatment with ≤11 follicles ≥12 mm. Group 1-3 were triggered with 5000 IU, 6500 IU or 10,000 IU HCG, respectively, receiving 17α-hydroxyprogesterone caproate intramuscularly for luteal-phase support (LPS) to measure endogenous progesterone production. Group 4 received 6500 IU HCG trigger and vaginal progesterone.