An intrauterine device (IUD) is a small, T-shaped contraceptive device inserted into the uterus by a healthcare provider. It is a highly reliable method of birth control with a failure rate of less than 1%. However, in some cases, the IUD can move from its correct position. This can result in partial or complete expulsion, where the device shifts or is pushed out entirely. This article explores the primary factors that contribute to displacement and expulsion and details the signs to watch for.
Uterine Factors and Anatomy
The most common and unavoidable causes of IUD movement are related to the natural function and structure of the uterus itself.
Strong Uterine Contractions
The uterus is a powerful muscle that regularly contracts, most noticeably during menstruation. For some individuals, these contractions can be strong enough to push the IUD out of its optimal position. The uterus may also perceive the IUD as a foreign body, triggering more intense contractions to expel it. This is a primary cause of displacement, particularly in the initial months after insertion while the body is still adjusting.
Heavy Menstrual Bleeding
There is a strong correlation between heavy menstrual bleeding (menorrhagia) and IUD expulsion. Studies indicate that individuals with heavy periods, and sometimes painful periods (dysmenorrhea), are at a significantly higher risk of expulsion. The forceful uterine contractions associated with heavy bleeding may contribute to the device being pushed out.
Uterine Shape and Size
The uterus's unique size and shape play a role in how well an IUD is retained. A uterus that is smaller than average, for instance due to congenital abnormalities like a bicornuate or arcuate uterus, may not accommodate the standard IUD size, increasing the risk of expulsion. In contrast, a uterus that has recently stretched, such as after a full-term pregnancy, may be a different size than before and cause improper fitting.
Fibroids or Polyps
Intrauterine abnormalities like fibroids or polyps can alter the shape of the uterine cavity. These growths can interfere with the IUD's fit, pushing against the device and causing it to dislodge over time. A healthcare provider typically evaluates the uterus for these conditions before insertion.
Factors Related to Insertion
Incorrect Placement
The skill and experience of the healthcare provider performing the insertion are critical. Improper placement of the IUD during the procedure is a leading cause of early displacement. A misplaced device may not seat correctly against the fundus (top) of the uterus, making it more vulnerable to movement or expulsion. A post-insertion check is usually recommended to ensure proper positioning.
Timing of Insertion
Research has shown that the timing of insertion relative to childbirth significantly impacts the risk of expulsion. Insertion immediately postpartum (within 10 minutes of placental delivery) and early postpartum (up to 4 weeks) have significantly higher expulsion rates than insertions performed during the standard interval period (four weeks or more after delivery). The uterus needs time to shrink back to its pre-pregnancy size and shape.
User-Related Factors and Myths
Menstrual Cup Use
While the evidence is conflicting, some studies have suggested a potential association between menstrual cup use and IUD expulsion, especially during the first year. The vacuum created by a menstrual cup during removal may theoretically pull on the IUD strings and dislodge the device. Users are often advised to break the suction seal before removal.
Tampon Use (Myth Debunked)
Contrary to popular belief, tampons do not cause IUD displacement when used correctly. The risk is minimal unless a dry tampon catches on the IUD strings and is pulled forcefully. The recommendation is to ensure the tampon is fully saturated and to remove it slowly and gently.
Vigorous Exercise or Sex (Myth Debunked)
Vigorous exercise, heavy lifting, or sex will not typically dislodge a properly placed IUD. The IUD is located high inside the uterus, well protected from external forces. The strings are designed to be thin and soft, and a partner feeling them is usually not a sign of displacement. If pain occurs during sex, it is wise to get checked, but the act itself is not a known cause of expulsion.
What to Do If You Suspect Displacement
If you believe your IUD has moved, it's essential to take action. Use a backup contraception method, such as condoms, until a healthcare provider can confirm the device's position.
Common Signs of IUD Displacement:
- Changes in string length (strings feel longer, shorter, or are missing).
- Feeling the hard plastic of the IUD at or near the cervical opening.
- Unusual or severe cramping and pelvic pain.
- Heavy, irregular, or unexpected bleeding or spotting.
- Pain during intercourse.
- Abnormal vaginal discharge.
The Diagnostic Process
Upon visiting a healthcare provider, the following steps are typically taken to assess the situation:
- Pelvic Exam: The provider will first check for the IUD strings during a pelvic exam. If the strings are missing or their length has changed significantly, it indicates potential displacement.
- Ultrasound: If the IUD cannot be located, an ultrasound is performed to determine if it is still within the uterus, has been expelled, or has embedded in the uterine wall.
- Removal: A partially expelled or displaced IUD must be removed. A new device can often be inserted during the same appointment, assuming no infection or other contraindications are present.
Comparison of IUD Expulsion Risks
| Factor | Copper IUDs | Hormonal IUDs | Notes |
|---|---|---|---|
| Expulsion Rate (First Year) | Varies, but studies show rates around 2.3% to 5.6%. | Varies, but studies show rates around 2.3% to 6.3%. | Expulsion is most common within the first three months for both types. |
| Risk of Expulsion by Age | Higher risk in younger users (14-19 years) compared to older women. | Higher risk in younger users (14-19 years) compared to older women. | Risk of expulsion decreases with age for both types of IUDs. |
| Heavy Bleeding Risk | Often causes heavier, more painful periods, which is a risk factor for expulsion. | Typically reduces or eliminates menstrual bleeding, potentially lowering the risk of expulsion. | Heavy menstrual bleeding is a significant risk factor for expulsion. |
| Postpartum Insertion | Associated with higher expulsion rates when inserted immediately or early postpartum. | Associated with higher expulsion rates when inserted immediately or early postpartum. | Expulsion rates are significantly higher for vaginal delivery insertions in the immediate postpartum period. |
| Device Shape | TCu380A design may have different expulsion risks than other copper IUD frames. | Different hormonal IUDs have different sizes (e.g., Mirena, Kyleena, Skyla), which can affect fit. | Device fit relative to uterine size is important for both types. |
Conclusion
While IUD expulsion is not a common event, it is a risk for all users, with most instances occurring early after insertion. Factors like strong uterine contractions, heavy periods, uterine abnormalities, and the timing and technique of insertion are the most significant contributors. Dispelling myths, such as the idea that sex or exercise can dislodge an IUD, is important for user peace of mind. Regular self-checking for the IUD strings and being aware of the signs of displacement are the best ways for users to monitor their device. If displacement is suspected, using a backup contraceptive and contacting a healthcare provider is the appropriate course of action to ensure continued protection and health. For more detailed information on IUD safety and guidelines, users can consult authoritative sources such as the American College of Obstetricians and Gynecologists.
