Emergency Contraception at 4 Days Post-Intercourse
At 4 days (96 hours) after unprotected sex, ulipristal acetate (UPA) 30 mg is the most effective oral emergency contraceptive option, while the copper IUD remains the single most effective method overall if insertion is feasible.
Primary Recommendations
First-Line Options
The copper IUD is the most effective emergency contraceptive at 4 days, with a failure rate of less than 1% and can be inserted up to 5 days after unprotected intercourse 1. This method provides the highest efficacy regardless of timing within the 5-day window and offers the added benefit of ongoing contraception 2.
Ulipristal acetate (UPA) 30 mg is the preferred oral option at 4 days after intercourse, as it maintains consistent effectiveness throughout the full 120-hour (5-day) window 1, 2. UPA is significantly more effective than levonorgestrel when taken 3-5 days after unprotected intercourse, with studies showing it prevents more pregnancies in this timeframe 1. The FDA label confirms UPA's efficacy when taken 48-120 hours after intercourse, with an observed pregnancy rate of 2.2% compared to an expected rate of 5.5% 3.
Why Not Levonorgestrel at 4 Days?
Levonorgestrel is NOT recommended at 4 days because its effectiveness decreases significantly after 72 hours, with pregnancy rates increasing substantially at 4-5 days post-intercourse 1, 2, 4. A meta-analysis demonstrated that levonorgestrel pregnancy rates were low within 4 days but increased notably at the 4-5 day mark 1. While levonorgestrel can technically be used up to 5 days, the evidence clearly shows reduced efficacy compared to UPA in this timeframe 5, 6.
Clinical Decision Algorithm
Step 1: Assess Patient and Timing
- Confirm the time since unprotected intercourse is approximately 96 hours (4 days) 2
- Verify negative pregnancy test before administering emergency contraception 3
Step 2: Choose Method Based on Availability and Patient Factors
If copper IUD insertion is available and acceptable:
- Insert copper IUD within 5 days of intercourse for maximum efficacy (<1% failure rate) 1, 2
- This provides ongoing contraception after insertion 2
If oral emergency contraception is preferred or IUD unavailable:
- Prescribe ulipristal acetate 30 mg as a single dose 1, 2, 3
- UPA is particularly important for women with higher BMI, as levonorgestrel may be less effective in obese women 1, 4, 7
Step 3: Post-Treatment Instructions
After UPA administration:
- Any regular contraceptive method can be started immediately 2, 4
- Critical: Use barrier contraception or abstain for 14 consecutive days (or until next menses) after UPA use 2, 4
- This extended backup period is necessary because UPA can interfere with hormonal contraception 2
After copper IUD insertion:
Important Caveats
Timing Matters
Even at 4 days, earlier is always better - efficacy decreases with each passing hour for all oral methods 4, 7. However, UPA maintains better efficacy than levonorgestrel throughout the 96-120 hour window 5, 6.
Weight Considerations
For women weighing >165 pounds or with obesity, UPA is significantly more effective than levonorgestrel regardless of timing 4, 7. The copper IUD remains the most effective option for all women regardless of weight 2, 7.
Follow-Up
Obtain a pregnancy test if withdrawal bleeding does not occur within 3 weeks of taking emergency contraception 8.
Common Pitfall
Do not assume levonorgestrel is adequate at 4 days simply because it can be used "up to 5 days" - the evidence clearly demonstrates reduced effectiveness compared to UPA at this timeframe 1, 2, 5.