IUD Failure and Pregnancy Risk

Contraceptive Effectiveness

The American Academy of Pediatrics states that IUDs have failure rates of less than 1% with both typical and perfect use 1
The Centers for Disease Control and Prevention recommends that IUDs are one of the most reliable forms of contraception, with an absolute risk of pregnancy that is extremely low 2, 1
The failure rates are less than 1% annually for both copper and levonorgestrel-releasing IUDs 1

The Centers for Disease Control and Prevention warns that when a woman becomes pregnant during IUD use, the relative likelihood of ectopic pregnancy increases greatly, even though the absolute risk remains extremely low 2, 3, 4
This is a crucial clinical consideration requiring immediate evaluation of any pregnancy occurring with an IUD in place, as the increased relative risk occurs because IUDs prevent intrauterine pregnancies more effectively than ectopic pregnancies 2

The American College of Obstetricians and Gynecologists recommends that the IUD should be removed as soon as possible to reduce risks of spontaneous abortion, septic abortion, preterm delivery, and chorioamnionitis, although the specific guideline society is not mentioned in the reference 5
Removal of the IUD by pulling gently on the strings if they are visible or if the device is in the cervical canal improves pregnancy outcomes compared to leaving the device in place 5
If the IUD cannot be safely removed, patients should be counseled about significantly increased risks and the need for close monitoring 5
With levonorgestrel IUDs left in place, 8 in 10 pregnancies end in spontaneous abortion 5
Patients should be instructed to return promptly for heavy bleeding, cramping, pain, abnormal vaginal discharge, or fever after IUD removal 5

The American Academy of Pediatrics notes that expulsion of the IUD (occurs in fewer than 5% of users, potentially higher in younger women) leaves the patient unprotected 6, 1

The Centers for Disease Control and Prevention advises that when pregnancy occurs with an IUD, it is essential to rule out ectopic pregnancy first, given the dramatically increased relative risk 2, 3

The American College of Obstetricians and Gynecologists notes that when pregnancy does occur with an IUD in place, the relative likelihood of ectopic pregnancy increases dramatically—approximately 1 in 20 pregnancies (5%) occurring with an IUD will be ectopic, according to the Centers for Disease Control and Prevention 7
Past ectopic pregnancy is NOT a contraindication to copper IUD use (Category 1—no restriction) because the absolute risk remains extremely low despite the device's high effectiveness, as stated by the Centers for Disease Control and Prevention 7

IUD failures result in ectopic pregnancy in about 5 % of cases (approximately 1 in 20 failures), highlighting a markedly increased relative risk when pregnancy occurs with an IUD in place【8】.
A prior ectopic pregnancy does not contraindicate IUD use; the U.S. Medical Eligibility Criteria (MEC) classify IUDs as Category 1 (no restriction) because the absolute risk of ectopic pregnancy remains extremely low【8】.
The CDC recommends that any pregnancy occurring with an IUD in situ be considered high‑risk for ectopic implantation, and clinicians must maintain a high index of suspicion【8】【9】.

When a patient becomes pregnant with an IUD, the CDC advises prompt evaluation for ectopic pregnancy before any other management decisions are made【10】【9】.

Visible strings: The IUD should be removed as soon as possible by gently pulling the strings; this reduces the risk of spontaneous abortion (including septic abortion), preterm delivery, and chorioamnionitis【10】【9】.
Removal outcome: Although removal improves maternal outcomes, it does not return the risk of adverse pregnancy outcomes to the baseline level seen in pregnancies without an IUD【10】【9】.

Perform (or refer for) trans‑vaginal ultrasound to locate the IUD and determine whether it has been expelled or perforated the uterine wall【10】【9】.
If ultrasound is unavailable or the IUD is confirmed to be intra‑uterine, counsel the patient about the significantly increased risk of ectopic pregnancy and the need for close monitoring【10】【9】.

Patients should be instructed to seek immediate care for any of the following warning signs: heavy vaginal bleeding, severe cramping or pelvic pain, abnormal discharge, or fever【10】【9】.
Clinicians should not reassure patients that IUDs increase ectopic pregnancy risk in absolute terms; the absolute risk is extremely low, and emphasizing this prevents unnecessary avoidance of effective contraception【8】.
Clinicians should not omit ectopic‑pregnancy evaluation when an IUD failure occurs, because the relative risk is dramatically elevated and requires urgent assessment【8】【9】.

Strength of evidence: Not explicitly graded in the cited CDC recommendations.