I have an IUD and am pregnant right now...and am wanting to know alot of answers!!
I also have an 10 year IUD. For almost 3 years now and in the last year I have became pregnant twice both ending in a miscarrage at 7 to 8 week along. Just long enough to find out that I was and then I wasn't.
Every birth control device or medication on the market has a failure rate, and the IUD is no different.
It is considered highly effective, though. You should not have to worry about conceiving while using it, but you should always be aware of pregnancy as a possibility, if you begin to have signs that you are pregnant.
Also...the IUD does not give you any protection against STD's, so if that is a concern, condoms should always be used along with it.