Hi Lav
My reflexology tutor (back in '97) taught that IUD's were a contraindication and to avoid the uterus reflex. What evidence for this is I don't know. Personally I think that working with the intent to stimulate healing within and create homeostasis, problems of that nature won't occur. Having said that my tutor was one for heavy pressures and digging into the ankles may cause uterine contractions.
Prehaps it depends on technique and what your belief system is. It wouldn't stop me treating a client with an IUD, I wouldn't use heavy pressure around the ankles anycase, it's too painful for most clients, and channelling/balancing energy on those points is more effective.
Best Wishes
Reflex Pixie