Progesterone (Cyclogest) support is required after egg collection as the follicles are ruined and ovarian progesterone production is impaired. Generally on the day of egg collection or next day is the usual time to start. This time is rather speculative without any evidence. Also some clinics recommend to use hCG injection (Pregnyl, Gonasi) to induce ovarian progesterone production. In this case progesterone support can be started later. Finally Cyclogest pessaries can be administered equally well via the back passage if you are worried about infection.