I have plan to began IUI treatment in 2011, by then I will be 33 years old.

Anon, you are fortunate to have such a regular cycle. When you begin IUI (IntraUterine Insemination), the process should be that much easier. And 33 is a great age to be trying.

Here is what one website says:

"How successful is IUI?
Natural IUIs, meaning that no fertility drugs were used, tend to have lower success rates, dipping down to about 6% in some cases. However, IUIs done with fertility drugs that produce multiple eggs have success rates of up to 30% associated with them. Additionally, sperm count greatly affects the outcome with IUI. Using sperm samples with a smaller count often cause less success. Overall, though, a success rate of 15% to 20% is associated with IUI."

And from another site:
"Success rates depend on you or your partner's fertility problem and your age. Most people who turn to IUI have a 5 to 20 percent chance of becoming pregnant with each cycle. Your chances will be closer to 20 percent if you take fertility drugs in conjunction with the procedure. There are no national statistics on live birth rates."

One of the reasons so many women use fertility medicine while doing IUI is to increase the possibility of pregnancy. It also helps pinpoint the exact time of ovulation. A cycle of IUI is expensive, and fertility medicine can increase your odds. Of course, it also increases the chance of multiple births.

Several websites for fertility or fertility centers do mention IUI without medication. Here are a couple:

http://www.sharedjourney.com/iui/faqs.html

http://www.infertilitydoctor.com/treat/iui.htm

http://www.ucsfivf.org/ucsf-iui.htm

And here's a fertility forum where women are talking about IUI without medicine:

http://forums.fertilitycommunity.com/intrauterine-insemination-iui/2020176463-anyone-doing-iui-au-natural-no-drugs.html

Sounds like it'll be very important for you to get a doctor who understands your desire to try IUI naturally. Quiz your fertility specialist right up front about their success rates without (and with) medication, and be sure you're happy with the answers you get before you proceed.