 Vaginal progesterone is used for luteal support in in vitro fertilization therapy and has been proven to effect pregnancy rates. However, the role of progesterone in COH is still unclear. In this study, the investigators want to examine the effect of giving vaginal progesterone after COH with IUI on pregnancy rates. The investigators want to study if luteal vaginal progesterone results in a higher pregnancy rate compared to no progesterone therapy in COH with IUI. At present, fertility centres vary in the use of progesterone after insemination, most likely due to the lack of studies on this subject. 