An intrauterine device (IUD) is a small, T-shaped contraceptive placed inside the uterus to prevent pregnancy. As a form of long-acting reversible contraception, it is over 99% effective, making it one of the most reliable birth control methods available. The device sits correctly at the top of the uterus, known as the fundus, where it is most effective. Although designed to remain securely in place for years, the IUD can rarely shift from this optimal position, a complication referred to as displacement or expulsion. Understanding how this movement occurs and what signs to look for is important for IUD users.
Mechanisms That Cause IUD Movement
The majority of IUD movement is attributed to dynamic forces within the uterus, primarily strong muscular contractions. The uterus is a powerful muscle, especially during menstruation, and these contractions can sometimes exert enough pressure to push the IUD downward out of its ideal placement in the fundus.
Expulsion is the partial or complete movement of the IUD out of the uterus and through the cervix, often happening in the first three months after insertion. A primary factor contributing to this is a mismatch between the size of the IUD and the dimensions of the uterine cavity. If the device is too large or too small, the body may attempt to expel it, which is more common in individuals who have not previously given birth.
Anatomical variations within the uterus also influence the device’s stability. Conditions such as uterine fibroids or congenital structural irregularities can alter the shape of the cavity, making it difficult for the IUD to sit securely. If the IUD is not properly seated, it may become malpositioned, shifting into the lower uterine segment or partially embedding in the uterine wall.
Another, though rare, form of displacement is perforation, where the IUD pushes through the uterine wall. This serious event can occur immediately during insertion if excessive force is used, or it can happen later as a secondary migration. Secondary perforation is thought to be caused by asymmetrical uterine forces gradually pushing the device into the muscle layer, allowing it to penetrate the myometrium over time.
Finally, the initial placement technique is a factor in maintaining position. If the IUD is not inserted correctly and seated firmly against the fundus, it can migrate downward later. Ensuring proper positioning during the procedure is a safeguard against subsequent displacement.
Recognizing the Signs of Displacement
One of the most common signs that an IUD has moved is a change in the length of the retrieval strings, which hang down through the cervix. If the strings feel noticeably longer or shorter than usual, or if they cannot be felt at all, the device may have shifted. However, strings can sometimes coil up inside the cervix, so a missing string warrants medical follow-up but does not definitively mean displacement.
Physical discomfort is another indicator of a displaced IUD. This can manifest as severe, persistent cramping not relieved by over-the-counter pain medication. Some people may also experience sharp pain during sexual intercourse, or their partner may feel the hard plastic tip of the IUD protruding from the cervix.
Changes in menstrual patterns, distinct from the typical side effects of IUD use, can also signal a problem. A sudden onset of heavy, irregular bleeding or spotting that is significantly different from previous cycles suggests contraceptive efficacy may be compromised. If the IUD has partially expelled, the protective effect is lost, increasing the risk of unintended pregnancy.
In cases of partial expulsion, the patient may even feel the bottom of the T-shaped device coming out of the cervix. Any of these symptoms, or the suspicion of pregnancy, means the IUD’s position is no longer reliable. It is important to avoid attempting to adjust the device and seek medical advice immediately.
Consequences and Medical Action
The most significant consequence of IUD displacement is the loss of contraceptive effectiveness. Once the device is no longer correctly positioned at the uterine fundus, the risk of unintended pregnancy increases substantially. This loss of protection means a barrier method of contraception, such as condoms, must be used immediately to prevent conception.
If displacement is suspected, a healthcare provider will first perform a pelvic examination to check the string length and feel for the device. The definitive diagnostic step is typically a transvaginal ultrasound, which allows the provider to accurately locate the IUD and confirm its position relative to the uterine fundus. If the device cannot be located within the uterus, an X-ray may be used to determine if it has migrated into the abdominal cavity.
Management for a displaced IUD usually involves removal. If the device is found in the lower uterine segment or partially expelled, it can often be removed during a simple office procedure. Following removal, the patient and provider can discuss options, including inserting a new, correctly sized IUD or selecting an alternative form of contraception.
Displacement can also lead to more serious complications, such as an increased risk of pelvic inflammatory disease (PID) or, rarely, an ectopic pregnancy if conception occurs. If the IUD has perforated the uterus and migrated into the pelvic or abdominal cavity, surgical intervention, such as laparoscopy, is required to retrieve it. This is necessary because a device outside the uterus carries a risk of damaging adjacent organs like the bowel or bladder.