An IUD can move out of its correct position because of uterine muscle contractions, a mismatch between the device’s size and the uterine cavity, or the timing of when it was placed. About 10 in 100 IUD users experience some degree of displacement within three years, and the rate is similar for both hormonal and copper types.
How Uterine Contractions Push the IUD
Your uterus is a muscular organ that contracts regularly, not just during your period. These contractions generate force that acts directly on the IUD sitting inside the cavity. When the forces are symmetrical, pushing evenly on all sides, the device stays put. But when there’s an imbalance, the combined muscle force points in a single direction, gradually nudging the IUD downward toward the cervix or, in rare cases, pressing it into the uterine wall.
This imbalance often comes down to a size mismatch. If the IUD is too small relative to the cavity, it can shift around more freely. If the uterine cavity is unusually shaped or enlarged, contractions may push unevenly against the device. The uterine muscle is strong enough, when applying force asymmetrically, to embed an IUD into the wall or push it partially out through the cervix.
Uterine Size and Shape
The dimensions of your uterine cavity play a surprisingly specific role. Research has identified a threshold of about 5.4 centimeters for the transverse (side-to-side) diameter of the uterus. Below that measurement, a slightly wider cavity actually helps stabilize the IUD, with each additional centimeter of width reducing the risk of malposition by about 74%. But once the cavity exceeds 5.4 cm, the relationship reverses sharply: each additional centimeter increases the risk of the IUD shifting by 112%.
Conditions that enlarge or distort the uterus can push the cavity past that threshold. Adenomyosis, fibroids, and congenital uterine anomalies (like a heart-shaped uterus) all change the internal geometry enough to make the IUD less stable. A provider may measure your uterine cavity before or during insertion, but subtle changes over time can also affect fit.
Timing of Insertion Matters
When the IUD is placed relative to childbirth is one of the strongest predictors of whether it will move. The uterus is dramatically larger and softer right after delivery, and it shrinks rapidly over the following weeks. An IUD placed during that shrinking process is more likely to end up in the wrong spot or get pushed out entirely.
The numbers are striking. IUDs placed within 10 minutes of delivering the placenta have an expulsion rate around 10%. Those placed between 10 minutes and four weeks postpartum fare worse, with expulsion rates near 30%. Waiting at least four weeks drops the rate to roughly 2%, which is comparable to insertion at any other time. Both immediate and early postpartum placements carry more than six times the expulsion risk compared to waiting. Many people still choose immediate postpartum placement because it guarantees they leave the hospital with contraception, but the tradeoff is real.
Age, Parity, and IUD Type
Whether you’ve given birth before (parity) affects expulsion risk, but the pattern depends on which type of IUD you have. For hormonal IUDs, women who have previously given birth have a higher 36-month expulsion rate (about 12.2%) compared to those who haven’t (6.9%). For copper IUDs, it’s the opposite: nulliparous women (those who haven’t given birth) have a 14.3% expulsion rate, while parous women sit around 8.2%. The reasons likely involve differences in cavity size and how each device interacts with the uterine lining.
Overall, the three-year expulsion rate is about 10 per 100 users for both hormonal and copper IUDs. A large study of over 322,000 women found nearly identical one-year expulsion rates of about 2.3% for both types, rising to roughly 4.5% at five years. Hormonal IUDs had a 30% lower expulsion risk overall, but a somewhat higher risk of perforation (where the device pushes through the uterine wall). Perforation, though, is rare for both types, occurring in fewer than 2 out of every 1,000 insertions.
Heavy Periods and Other Triggers
Heavy menstrual bleeding has been linked to higher expulsion risk, likely because the stronger, more frequent contractions that produce heavy flow also generate more force against the IUD. The cervix dilates slightly more during heavy periods, giving the device a wider exit path. Using a menstrual cup has also been flagged as a possible contributor, since the suction created when removing the cup could tug on the IUD strings, though evidence on this is limited.
Physical activity, including exercise and sex, does not reliably cause an IUD to move. The device sits inside the uterine cavity, which is a separate space from the vaginal canal. Vigorous movement won’t dislodge it. However, if an IUD is already partially displaced, intercourse might cause you or your partner to feel the hard plastic tip protruding into the vaginal canal.
Signs Your IUD Has Shifted
A slight shift may cause no symptoms at all. Many women with a low-lying IUD never know it’s moved until an imaging scan. But a more significant displacement tends to announce itself. The most reliable self-check involves your IUD strings: they hang about two inches into the vaginal canal, and you can feel them with the tip of your longest finger. If the strings feel noticeably longer, shorter, or have disappeared entirely, the IUD may have moved.
Other signs depend on which type you have. With a hormonal IUD, unexpected heavy or period-like bleeding is a red flag, especially if you’d gotten used to a lighter flow or no bleeding at all. With a copper IUD, a sudden change in your period pattern, lighter than usual, or a shift in cycle length, can signal displacement. Both types can cause sharp, sudden cramping, unusual discharge, or pain during sex if the device has shifted significantly. If the IUD has partially come out, you or a partner may be able to feel the hard plastic tip of the device itself, not just the strings.
What Happens if It Moves
Not every displaced IUD needs to come out. According to guidance from the American College of Obstetricians and Gynecologists, the decision depends on where the IUD has ended up and whether you’re having symptoms. An IUD that has slipped down into the cervix is considered partially expelled and should be removed, since it’s likely to come out on its own and isn’t providing reliable contraception. But an IUD that’s sitting low in the uterus while still above the cervical opening is a different situation.
If you have no symptoms and the device is above the internal opening of the cervix, leaving it in place is often the better option. Removing a low-lying IUD is more likely to result in an unintended pregnancy than keeping it, because many people don’t immediately replace it with equally effective contraception. Many IUDs that appear low shortly after insertion actually migrate upward to the correct fundal position within three months. Removing and replacing them all would mean a lot of unnecessary procedures.
Perforation, where the IUD passes partially or fully through the uterine wall, is the most serious form of movement but also the rarest. It happens in roughly 1 in 1,000 insertions. It can be completely asymptomatic or cause persistent low abdominal pain and “lost” strings (where you can no longer feel them). In extremely rare cases where the device migrates into the abdominal cavity and contacts the bowel or bladder, symptoms can include fever, changes in bowel habits, or urinary problems. Perforation is typically detected by ultrasound and usually requires a minor procedure to retrieve the device.