It is well known that implantation of the developing blastocyst occurs during the luteal phase of the menstrual cycle when the endometrium is under the direct influence of Progesterone (P).Several prospective randomized controlled trials have evaluated the benefits of luteal phase P support in ovulation induction cycles and a recent review and meta-analysis demonstrated that it may be of benefit to patients undergoing ovulation induction with gonadotropins in intrauterine insemination (IUI) cycles. Until now, injectable P was offered only in an oil-base solution owing to the insoluble properties of the molecule, which made the IM route mandatory. A recent publication, however, demonstrated the efficacy of a new P formulation that could be a game changer. The aim of the present pilot trial will be to compare the efficacy and tolerability of 25 mg/d of the new SC P with 90 mg/d of vaginal gel P for luteal phase support (LPS) in COH and IUI cycles.