Earlier quoted context omitted.
>>IUDs dont fail They absolutely do, and it's often life threatening when it happens. It's very unlikely, but it's not absolute protection. https://www.webmd.com/sex/birth-control/get-pregnant-iud
It does say that the baby's and the mother's health could be in danger, but where does it say it's often life threatening? Never heard about an IUD failing at all so thanks for the link anyhow
IUDs greatly reduce overall risk of pregnancy. The risk is not zero, though. When IUDs do fail, and they will, they increase the risk of ectopic pregnancies. The vast majority of those are located in the uterine tubes. Those are life threatening. There is no space for the fetus in the tube, it will rupture and cause severe bleeding which can and will kill the mother if left untreated. It's an important cause of acute abdomen.