 At the Fertility Clinic all patients undergoing COH with injectable medications and IUI, regardless of whether they are in the study, have a baseline transvaginal ultrasound and blood tests. Patients start the injectable medications for COH until the ovarian follicles are large enough, then a medication to release the eggs is given. The IUI is done approximately 36 hours later. The day after the IUI, study patients will be given vaginal progesterone while the control patients will receive no progesterone. All patients will be followed until a pregnancy test is done and a viable foetus is confirmed by ultrasound. 