Ladies I have an IUI question please help.

My wife is having an ultrasound on Wednesday to see when she will ovulate. And once we know, our known donor will go get his sperm washed. My question is, how many times do you go and get IUI in one cycle? We are only doing it once and I don't know what the chances are on getting pregnant with just one try. She won't be taking any fertility drugs. This will be out first try with IUI at a doctor's office. Any comments or advice will help.