5.1 Long-Acting Reversible Contraception (LARC): IUDs & Subdermal Implants
Key Takeaways
Long-acting reversible contraceptives (LARCs), including intrauterine devices and the subdermal implant, provide Tier 1 contraceptive efficacy with typical-use failure rates under 1% (<0.1% for implant, 0.1–0.2% for LNG-IUS, 0.8% for Cu-IUD), completely removing adherence requirements.
The Copper T 380A IUD (Paragard) is non-hormonal, FDA-approved for up to 10–12 years, acts via a sterile spermicidal foreign-body inflammatory reaction, serves as the gold-standard emergency contraceptive within 5 days of coitus, and characteristically increases menstrual volume and dysmenorrhea.
Levonorgestrel intrauterine systems (52 mg Mirena/Liletta [8 years], 19.5 mg Kyleena [5 years], 13.5 mg Skyla [3 years]) act locally via cervical mucus thickening and profound endometrial decidualization/atrophy, inducing amenorrhea in 20% to 50% of 52 mg users at 1 year, making 52 mg LNG-IUS first-line therapy for heavy menstrual bleeding.
The single-rod etonogestrel implant (Nexplanon, 68 mg; FDA-approved for up to 5 years since January 2026 and dispensed through a REMS program) achieves Tier 1 efficacy primarily via pituitary LH suppression (ovulation inhibition) and cervical mucus thickening; prospective counseling regarding unpredictable, non-cyclical bleeding is the single most effective intervention to prevent premature discontinuation.
LARC complications are managed conservatively: acute mild-to-moderate pelvic inflammatory disease is treated with broad-spectrum antimicrobials with the IUD in situ unless no clinical improvement is observed after 48–72 hours; missing strings require sequential evaluation with a cytobrush, transvaginal ultrasound, and abdominal radiography if perforation is suspected.
Tier 1 Efficacy & Clinical Rationale for LARC
Contraceptive methods are stratified into three clinical tiers based on typical-use failure rates:
- Tier 1 (<1% failure rate): Long-acting reversible contraceptives (LARCs)—including intrauterine devices (IUDs) and subdermal implants—alongside permanent sterilization. These "set-and-forget" methods eliminate user compliance and adherence errors.
- Tier 2 (4–9% failure rate): Injectables, oral contraceptive pills, transdermal patches, and vaginal rings.
- Tier 3 (10–25%+ failure rate): Barrier methods, fertility awareness-based methods (FABMs), withdrawal, and spermicides.
LARC methods combine Tier 1 efficacy with immediate return of baseline fecundity upon removal. One-year continuation rates for LARCs exceed 80–88%, compared to roughly 50–60% for short-acting methods. ACOG and the CDC endorse LARCs as first-line options for all reproductive-age individuals, including nulliparous women and adolescents.
Copper Intrauterine Device (Paragard)
The Copper T 380A (Paragard) features a radiopaque polyethylene T-frame wrapped with 380 mm² of exposed copper wire on the stem and arms.
- Mechanism of Action: Continuous release of copper ions into the uterine cavity and fallopian tubes produces direct spermicidal cytotoxicity, inhibiting sperm motility, capacitation, and acrosome reaction. The foreign body also induces a sterile endometrial inflammatory reaction, preventing fertilization. It does not disrupt established post-implantation pregnancy.
- Duration of Use: FDA-approved for up to 10 years; clinical trials demonstrate efficacy for up to 12 years.
- Emergency Contraception (EC): Serves as the gold standard for postcoital EC when placed within 5 days (120 hours) of unprotected intercourse (>99.9% efficacy).
- Bleeding Profile & Management: As an entirely non-hormonal method, endogenous ovulatory cycles persist. The primary side effect is increased menstrual bleeding (30–50% increase) and dysmenorrhea, predominantly during the first 3 to 6 months. First-line management consists of scheduled NSAIDs (e.g., ibuprofen 600–800 mg TID or mefenamic acid 500 mg TID with meals) taken 1 to 2 days prior to or at menses onset for the first 5 days.
Levonorgestrel Intrauterine Systems (LNG-IUS)
Four levonorgestrel-releasing intrauterine systems are available in the United States:
| Device Name | Total LNG Mass | Initial Daily Release | Approved Duration | Dimensions & Inserter Outer Diameter | Expected 1-Year Amenorrhea | Clinical Distinctions |
|---|---|---|---|---|---|---|
| Mirena | 52 mg | ~20 mcg/day | Up to 8 years | 32 x 32 mm; Inserter: 4.4 mm | 20% (up to 50% by 5 yr) | FDA-indicated for contraception and heavy menstrual bleeding (HMB). |
| Liletta | 52 mg | ~20 mcg/day | Up to 8 years | 32 x 32 mm; Inserter: 4.8 mm | 19% to 24% | FDA-indicated for contraception and HMB; public health pricing. |
| Kyleena | 19.5 mg | ~17.5 mcg/day | Up to 5 years | 28 x 30 mm; Inserter: 3.8 mm | 12% | Smaller frame and inserter; silver ring for ultrasound visibility. |
| Skyla | 13.5 mg | ~14 mcg/day | Up to 3 years | 28 x 30 mm; Inserter: 3.8 mm | 6% | Smallest frame; lowest systemic absorption; lower amenorrhea rate. |
Mechanism of Action & Bleeding Profiles
LNG-IUS devices act primarily via profound local progestogenic effects: thickening cervical mucus into an impenetrable barrier within 24–48 hours, inducing stromal decidualization and glandular atrophy, and altering uterotubal transport. Ovulation is maintained in the majority of cycles, preserving endogenous estradiol levels.
Unscheduled spotting is common during the first 3 to 6 months. With ongoing endometrial atrophy, flow decreases substantially; by 12 months, 20% to 50% of 52 mg LNG-IUS users develop amenorrhea or oligomenorrhea. Patients should be reassured that amenorrhea results from local endometrial suppression rather than premature menopause or retained blood.
Etonogestrel Subdermal Implant (Nexplanon)
Nexplanon is a single radiopaque ethylene vinyl acetate rod (4 cm x 2 mm) containing 68 mg of etonogestrel, preloaded in a disposable applicator.
- Mechanism & Efficacy: Releases 60–70 mcg/day initially, decreasing to 25–30 mcg/day at 3 years. Its primary mechanism is complete ovulation suppression via pituitary LH surge inhibition, supported by rapid cervical mucus thickening. With a failure rate <0.1%, it is the most effective reversible contraceptive available. In January 2026 the FDA extended approval from 3 to 5 years and placed the implant under a REMS program that requires trained, certified inserters.
- Bleeding Pattern Counseling: Unpredictable, non-cyclical bleeding is the most common side effect and leading reason for discontinuation (~30% infrequent bleeding, ~20% amenorrhea, ~15–20% frequent/prolonged spotting). The 90-day bleeding pattern predicts long-term bleeding. Bothersome bleeding is managed with a 5- to 7-day course of scheduled NSAIDs (ibuprofen 800 mg TID) or a 10- to 20-day course of low-dose combined oral contraceptives (30–35 mcg EE); US SPR 2024 also lists a 5-day course of tranexamic acid or a 7–10-day course of tamoxifen.
- Insertion & Non-Palpable Rods: Placed subdermally in the non-dominant upper inner arm, 8–10 cm proximal to the medial humeral epicondyle, avoiding the biceps-triceps sulcus. Palpation is verified immediately. Non-palpable rods mandate immediate backup contraception; blind exploration is contraindicated. Localize via high-frequency ultrasound (≥10 MHz), non-contrast MRI, or serum etonogestrel assay, followed by specialized surgical extraction.
Clinical Insertion Protocols & Complication Management
- Insertion Timing: LARCs can be initiated anytime during the cycle if pregnancy is reasonably excluded (quick start). Backup contraception for 7 days is needed if an implant is placed >5 days, or an LNG-IUD >7 days, after menstrual bleeding started (none for the copper IUD; US SPR 2024). Immediate post-abortion placement is safe and effective. Immediate postplacental placement (within 10 minutes of placental delivery; US MEC 2024 Category 2 for both IUD types) has higher expulsion rates (10–25%) than delayed placement at 4–6 weeks (2–5%), but delivers significantly higher 1-year continuation.
- Lost Strings & Perforation: If strings are absent at the os, probe the canal with a cytobrush. If unretrieved, obtain a urine pregnancy test and transvaginal ultrasound. If the uterine cavity is empty, obtain abdominal/pelvic radiographs to evaluate for peritoneal perforation. Uterine perforation occurs in ~1 per 1,000 insertions; major risk factors include active lactation (~6-fold increase due to uterine softening) and insertion ≤36 weeks postpartum.
Important
If acute pelvic inflammatory disease (PID) develops with an IUD in situ, initiate CDC-recommended broad-spectrum antibiotics with the IUD in place. Immediate removal does not accelerate recovery. Remove the device only if clinical improvement is absent after 48 to 72 hours of antimicrobial therapy.
A 22-year-old nulliparous college student presents requesting highly effective contraception. She is interested in a levonorgestrel intrauterine system (LNG-IUS) but mentions she was previously told by a provider that IUDs are contraindicated in women who have never had children because of an elevated risk of pelvic inflammatory disease (PID) and future infertility. What is the most evidence-based clinical guidance to provide this patient?
Intrauterine devices are approved only for parous women because nulliparous uterine anatomy results in a 50% expulsion rate.
LNG-IUS placement should be deferred until age 25 due to an unacceptable risk of ascending Chlamydia trachomatis pelvic infection in nulliparous adolescents and young adults.
Both copper IUDs and LNG-IUS devices are safe, highly effective first-line contraceptive options for nulliparous individuals, with no increased risk of PID beyond the first 20 days post-insertion.
Nulliparous individuals should exclusively use the single-rod etonogestrel implant because uterine sounding below 7 cm is an absolute contraindication to IUD insertion.
A 26-year-old woman with a 52 mg levonorgestrel intrauterine system (Mirena) inserted 9 months ago presents to the clinic complaining of bilateral lower quadrant pelvic pain, fever (38.2°C / 100.8°F), and purulent vaginal discharge for 3 days. Bimanual pelvic examination reveals marked cervical motion tenderness and bilateral adnexal tenderness without palpable masses. A clinical diagnosis of acute mild-to-moderate pelvic inflammatory disease (PID) is established. The patient is hemodynamically stable, tolerating oral fluids, and has no signs of peritonitis. What is the most appropriate management plan regarding her IUD?
Start outpatient ceftriaxone, doxycycline, and metronidazole, leave the IUD in place, and reassess in 48–72 hours.
Remove the IUD immediately before administering any antimicrobial agents to eliminate the microbial biofilm nidus.
Administer an intramuscular dose of ceftriaxone, remove the IUD 1 hour later, and transition to combined oral contraceptives.
Hospitalize the patient immediately for emergent surgical removal of the IUD and diagnostic laparoscopy.
A 29-year-old woman presents for follow-up 6 months after the insertion of a single-rod etonogestrel subdermal implant (Nexplanon). She is frustrated by unpredictable, light vaginal bleeding and spotting occurring every 10 to 14 days. She denies pelvic pain, fever, or dyspareunia. Her urine pregnancy test is negative, and a speculum examination is unremarkable with no cervicitis. What is the most appropriate first-line clinical management for this patient?
Recommend immediate surgical removal of the implant because irregular bleeding after 6 months indicates loss of contraceptive efficacy.
Reassure her that unpredictable bleeding is the most common benign implant side effect, and offer 5–7 days of scheduled NSAIDs.
Administer intramuscular medroxyprogesterone acetate 150 mg to induce complete endometrial desquamation.
Prescribe high-dose oral conjugated estrogens (1.25 mg daily) continuously for 6 months to regenerate endometrial spiral arterioles.
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