Can you tell me, are women with iuds more prone to infections?

Probably not...: ...at least not serious infections. When IUDs were new, they seemed to predispose to pelvic inflammatory disease (PID, fallopian tube infection). It turned out this was a problem for just one type, the Dalkon Shield, no longer on the market. IUDs today rarely cause serious infections. But to be safe, if a vaginal infection, STD, etc is present, insertion is delayed until cured.