What is withdrawal bleeding in a female patient who took levonorgestrel (emergency contraceptive)?

What is Withdrawal Bleeding After Levonorgestrel Emergency Contraception?

Withdrawal bleeding is the menstrual period that occurs after taking levonorgestrel emergency contraception, representing the hormonal response to the medication and serving as a key indicator that pregnancy has been prevented. 1, 2

Definition and Mechanism

Withdrawal bleeding after levonorgestrel is the menstrual bleeding that follows the hormonal disruption caused by the emergency contraceptive pill. 1 This bleeding occurs because:

• Levonorgestrel works by stopping or delaying ovulation through its high progestin dose, similar to how regular birth control pills function but at a much higher concentration. 3
• The subsequent drop in hormone levels after the medication is metabolized triggers endometrial shedding, resulting in withdrawal bleeding. 1

Expected Timing and Patterns

You should expect withdrawal bleeding to occur within 3 weeks of taking levonorgestrel, though the exact timing depends on when in the menstrual cycle the medication was taken. 1, 2, 3

Timing Variations:

• If taken early in the cycle (first 3 weeks): The menstrual period typically arrives earlier than expected, with the cycle being significantly shortened. 4
• The earlier in the cycle levonorgestrel is taken, the more pronounced the cycle shortening effect. 4
• Most women (69%) experience early or timely return of menses, while 21% have menses delayed by more than a week. 5

Bleeding Pattern Variations:

• Normal bleeding patterns occur in only 57% of women, while others experience alterations including intermenstrual bleeding/spotting, premenstrual bleeding/spotting, or heavier bleeding. 5
• The duration of the first menstrual period after treatment increases significantly with the cycle week when treatment was taken. 4
• Intermenstrual bleeding is uncommon, occurring in only 5% of women in the first cycle after treatment. 4

Critical Clinical Threshold

If withdrawal bleeding does not occur within 3 weeks of taking levonorgestrel, a pregnancy test must be performed immediately. 1, 2, 3 This is the most important safety threshold because:

• Absence of bleeding beyond 3 weeks may indicate pregnancy, as levonorgestrel will not work if the patient is already pregnant. 3
• The CDC explicitly recommends this 3-week cutoff as a key clinical decision point. 1, 2

Reassurance Points for Patients

All bleeding changes after levonorgestrel are transient and generally resolve by the next cycle. 2 Patients should understand:

• These menstrual disturbances are expected side effects and not harmful. 2, 5
• Approximately 30-43% of users experience prolonged or altered bleeding patterns, but these are temporary. 2
• The medication does not affect an existing pregnancy and will not protect against sexually transmitted infections. 3

Contraceptive Resumption After Levonorgestrel

Any regular contraceptive method can be started immediately after levonorgestrel use, but the patient must abstain from intercourse or use barrier contraception for 7 days. 1, 2 This is important because:

• The bleeding irregularities do not contraindicate starting regular hormonal contraception. 2
• Unlike ulipristal acetate (which requires 14 days of barrier backup), levonorgestrel only requires 7 days due to the absence of antiprogestin properties. 1

Common Pitfalls to Avoid

• Never dismiss the absence of withdrawal bleeding at 3 weeks—this mandates pregnancy testing regardless of other factors. 1, 2, 3
• Do not confuse withdrawal bleeding with treatment failure—bleeding changes are expected and do not indicate the medication didn't work. 2, 4
• If the patient vomits within 2 hours of taking levonorgestrel, another dose should be taken as the medication may not have been absorbed. 3