Copper
"I ended up in the ER for serious pains after vomiting for over 24 hours, feeling like a case of severe food poisoning. I realized my lower abdomen was swollen and warm to the touch. When I pushed on it, I felt a sharp pain in my uterus. Doctors took an ultrasound and couldn't locate it at first because it had moved from the original position, perforating my uterus. They were able to surgically remove it, thankfully. I would not recommend anyone get one."