It is made in different shapes depending on the manufacturer. The IUD is inserted through the cervix and into the uterus to prevent the newly fertilized egg from implanting. The exact action is not known but it is thought that implantation is prevented by the 'foreign body' reaction in the lining of the uterus. If a patient becomes pregnant with an IUD in place, septic abortion and septic shock and death can occur. There is an increase in ectopic pregnancy in IUD users.
Pelvic infection is common.
An increased risk of tubal infertility has been observed in IUD users and this increase is significant enough that women are cautioned to discuss the option at length with their doctors before inserting the device. Partial embedding of the IUD can cause difficulty in removal. Perforation of the uterus can occur. This can be a silent process until widespread infection is apparent. The IUD can come out or travel to the wrong place.