An intrauterine device (IUD) is a small, T-shaped form of long-acting reversible contraception inserted into the uterus to prevent pregnancy. Both hormonal and copper IUDs boast an effectiveness rate exceeding 99% when correctly placed. The device offers long-term protection, lasting anywhere from three to twelve years, depending on the specific type. For the device to function optimally, its position within the uterine cavity is important.
Normal Versus Low IUD Placement
Correct placement of an IUD requires it to be situated high within the uterine cavity, specifically in the fundus. The fundus is the dome-shaped upper portion of the uterus. This high position ensures the device’s mechanisms of action are fully engaged, with its horizontal arms fully extended across the top of the cavity.
A low-lying IUD has migrated downward from this optimal fundal location. Clinicians define this malposition as the IUD being located more than two centimeters below the fundus. This descent changes the anatomical relationship of the device, compromising its ability to prevent conception. In cases of partial expulsion, a portion of the IUD or its stem may extend into the cervical canal.
How Effectiveness Changes
A low-lying IUD has reduced contraceptive efficacy compared to a correctly placed one. Displacement significantly increases the risk of unintended pregnancy above the baseline rate. Providers advise patients to assume the device is no longer fully effective and to use a backup contraceptive method immediately.
The mechanism of failure differs between IUD types. Copper IUDs prevent pregnancy primarily by creating an inflammatory reaction toxic to sperm and eggs. This spermicidal effect is greatest when the copper is situated close to the top of the uterus where fertilization takes place. Downward displacement reduces this localized coverage, lessening the spermicidal field and increasing the chance of fertilization.
Hormonal IUDs release a progestin hormone that thickens cervical mucus and thins the uterine lining. A low position can compromise the local hormone delivery needed to suppress the endometrium and maintain the hostile environment for sperm. Any significant displacement of either type of IUD warrants clinical attention and a change in contraceptive strategy.
Identifying a Low-Lying IUD
Patients may experience signs and symptoms if their IUD has moved out of position. The most common indicator is a change in the length of the IUD strings felt during a self-check. The strings may feel noticeably longer than usual or become completely absent, suggesting a partial expulsion or a shift in orientation.
Symptoms of Displacement
New or worsening pelvic pain and cramping may occur after the initial insertion period. Abnormal uterine bleeding, such as heavier flow or spotting between periods, may also signal displacement. In cases of partial expulsion, the hard plastic tip of the IUD may be felt protruding from the cervix.
Diagnosis
When displacement is suspected, a healthcare provider performs a pelvic exam to check the strings. Transvaginal ultrasound is the standard diagnostic tool used to confirm the IUD’s precise location relative to the uterine fundus and cervical canal. If the device cannot be visualized within the uterus by ultrasound, X-rays of the pelvis may be used to determine if the IUD has perforated the uterine wall and migrated into the abdominal cavity.
Management of a Displaced IUD
Once a low-lying IUD is confirmed by imaging, the primary course of action is removal. Repositioning is generally not recommended, as it is often ineffective and the device is likely to migrate again. The removal process is typically straightforward and performed in the provider’s office.
Following removal, the patient may have a new IUD inserted immediately, provided there are no contraindications like infection. Alternatively, the patient may switch to a different contraceptive method, such as an oral pill, implant, or injection. Discussing the cause of displacement is essential, as a recurrent issue may suggest a different method is more appropriate.
During the period before removal or replacement, the use of barrier methods, such as condoms, is strongly advised. Backup protection is required because the low-lying IUD cannot be depended upon to prevent pregnancy.