My RE does exactly what you asked about. They time the HCG to be right at 36 hours before IUI. One way they do it is by setting a specific IUI time. They do them at 11 am. The patient does the HCG trigger 36 hours before IUI (so 11 pm 2 days before the procedure). I administered my trigger last night, and my IUI is tomorrow at 11.
2/10/11 at 8:40am