Emergency Contraception

Methods Available

1. Levonorgestrel (Progestin-Only Pill) - First-Line Oral Option

• Dose: 1.5 mg as a single dose (or two doses of 0.75 mg 12 hours apart - equally effective but less convenient)
• Window: Labeled for use within 72 hours of intercourse; the WHO permits use up to 120 hours though efficacy declines with time
• Efficacy: Prevents approximately 85% of expected pregnancies when used within 72 hours; most effective when taken within 24 hours
• Prescription: Available over-the-counter in the United States (since 2013 for all ages)
• Mechanism: Delays or inhibits ovulation. It works only if taken before ovulation - it is not an abortifacient. Studies confirm no pregnancies occurred in 87 women who took levonorgestrel 1-5 days before their expected ovulation day
• Side effects: Nausea, headache, irregular menstrual bleeding (resolves spontaneously within 1 week to 1 month)
• BMI concern: Evidence suggests reduced effectiveness at higher BMI; an increased dose may be needed in obese patients, though further study is required before a definitive recommendation

2. Ulipristal Acetate (UPA) - Preferred at 72-120 Hours

• Dose: 30 mg single tablet (brand name: ella)
• Window: Approved for up to 120 hours after intercourse; remains effective beyond the 72-hour levonorgestrel window
• Prescription required: Yes, by prescription only
• Efficacy: Superior to levonorgestrel when ovulation is imminent. Odds of pregnancy were 42% lower than levonorgestrel within 72 hours, and 65% lower in the first 24 hours. It works by delaying follicular rupture for 5+ days when the LH surge has already begun
• Mechanism: Selective progesterone receptor modulator (SPRM) - delays ovulation even when the LH peak is already occurring, giving it a wider effective window than levonorgestrel
• Side effects: Similar to levonorgestrel (nausea, headache); significantly less nausea than the combined estrogen-progestin (Yuzpe) regimen

3. Combined Oral Contraceptives - Yuzpe Regimen (Largely Obsolete)

• Dose: 100 mcg ethinyl estradiol + 0.5-1.0 mg levonorgestrel, taken in two doses 12 hours apart
• Largely fallen out of favor due to high rates of nausea (50.5% vs. 23.1% with levonorgestrel alone) and vomiting (18.8% vs. 5.6%), and lower efficacy (pregnancy rate 3.2% vs. 1.1% with levonorgestrel alone in the landmark WHO RCT of 1,998 women)
• Also associated with case reports of thrombotic events (not seen with levonorgestrel alone)

4. Copper Intrauterine Device (IUD) - Most Effective Option

• Window: Must be inserted within 5 days of intercourse; effective up to 7 days in some studies (approaching near-100% efficacy)
• Efficacy: Essentially 100% - the most effective form of EC available. Compared to 89% for progestin-only pills and 74% for Yuzpe regimen
• Mechanism: Inhibits sperm function, motility, and capacitation through a sterile inflammatory reaction; prevents fertilization (not implantation). The copper ions augment this effect. Unlike levonorgestrel/ulipristal, it does not require any timing relative to ovulation
• Ongoing benefit: The same copper IUD (ParaGard, Cu-T380A) provides highly effective contraception for up to 20 years. In one large trial, 94% of women continued using it at 12-month follow-up with no uterine perforations
• Risks: ~1/1000 risk of uterine perforation; uterine cramping is common
• Barrier to use: Requires a clinic appointment with a qualified provider within the time window; upfront cost in some settings

Note from Goldman-Cecil Medicine: A levonorgestrel 52 mg IUD (Mirena) has also shown efficacy as EC when inserted within 5 days of unprotected intercourse, though this is a more recent finding.

Comparative Summary

Mechanism of Action - Key Clarification

Counseling Points

• All methods are most effective the sooner they are taken
• Pregnancy remains possible in the same menstrual cycle after oral EC; patients should use a backup contraceptive method
• A pregnancy test should be done if menstruation is delayed by more than 3 weeks
• Irregular bleeding within 1 week to 1 month after oral EC is common and resolves without intervention
• EC is not intended to replace regular contraception; follow-up counseling on ongoing birth control is recommended
• Only 9% of women choose the copper IUD for EC despite its superior efficacy, largely due to access barriers (clinic visit, cost, misconception about 10-year requirement - it can be removed at any time)

Emergency Contraception

Available Methods

1. Levonorgestrel (Plan B, progestin-only) - First-line OTC option

• Dose: 1.5 mg single dose (or 0.75 mg × 2 doses, 12 h apart - equally effective)
• Window: Up to 72 hours (WHO allows up to 120 h)
• Efficacy: ~85% reduction in expected pregnancies
• Prescription: OTC (no prescription needed in the US)
• Mechanism: Delays/inhibits ovulation; works only if taken before ovulation - not an abortifacient
• Side effects: Nausea, headache, irregular bleeding (self-resolving within 1 month)
• BMI note: Reduced efficacy at higher BMI; higher dose may be considered but not yet definitively recommended

2. Ulipristal Acetate (ella, SPRM) - Preferred beyond 72 hours

• Dose: 30 mg single tablet
• Window: Up to 120 hours - maintains efficacy when levonorgestrel's has declined
• Efficacy: Odds of pregnancy 42% lower than levonorgestrel by 72 h; 65% lower in first 24 h; superior when ovulation is imminent (LH surge already begun)
• Prescription: Required
• Mechanism: Delays follicular rupture for 5+ days even after LH peak begins

3. Yuzpe Regimen (combined OCP) - Largely obsolete

• Dose: 100 mcg ethinyl estradiol + 0.5-1.0 mg levonorgestrel in 2 doses, 12 h apart
• Efficacy: ~74% - inferior to both options above
• Abandoned due to significantly higher nausea (50.5% vs. 23.1%) and vomiting (18.8% vs. 5.6%), and case reports of thrombotic events not seen with levonorgestrel alone

4. Copper IUD (Paragard) - Most effective option

• Window: Up to 5 days (near-100% efficacy); some evidence supports up to 7 days
• Efficacy: ~100% - far superior to any oral method (vs. 89% for LNG pills, 74% for Yuzpe)
• Mechanism: Sterile inflammatory reaction toxic to sperm - inhibits sperm motility, capacitation, and survival; prevents fertilization
• Advantages: Provides ongoing contraception for up to 20 years; 94% of women continue using it at 12 months
• Risks: ~1/1,000 uterine perforation; cramping
• Barrier: Requires clinic visit within the time window; upfront cost

New data (Goldman-Cecil): The levonorgestrel 52 mg IUD (Mirena) has also demonstrated efficacy as EC when inserted within 5 days of unprotected intercourse.

Side-by-Side Comparison

Key Counseling Points

• Take as soon as possible - all methods are most effective within 24 hours
• EC does not protect against pregnancy for the rest of the cycle - advise backup contraception
• Pregnancy test if next period is delayed >3 weeks
• Irregular bleeding within 1-4 weeks after oral EC is normal and self-resolving
• EC is not an abortifacient - all methods prevent ovulation or fertilization; none affect an implanted embryo
• Despite the copper IUD's clear superiority, only ~9% of women choose it for EC, largely due to access barriers and the misconception that it must remain in place for 10 years (it can be removed at any time)
• Follow-up counseling on ongoing contraception is always recommended