Levonorgestrel Emergency Contraception Is NOT Contraindicated in Pregnancy
Levonorgestrel emergency contraception is classified as "Not Applicable" for use in pregnancy—not because it is contraindicated, but because it serves no purpose once pregnancy has already occurred. The medication will not harm an existing pregnancy, the mother, or the fetus if inadvertently taken. 1, 2
Why This Misconception Exists
The confusion arises from misunderstanding the difference between "contraindicated" (harmful and should not be used) versus "not indicated" (serves no purpose but causes no harm):
- Emergency contraceptive pills are not indicated for known or suspected pregnancy because they work by preventing ovulation and fertilization—mechanisms that are irrelevant once pregnancy has begun 1
- No harm to the woman, pregnancy course, or fetus occurs if ECPs are inadvertently used during early pregnancy 1, 2
- The FDA drug label explicitly states: "Levonorgestrel tablet will not work if you are already pregnant and will not affect an existing pregnancy" 2
Mechanism of Action Clarifies Safety
Understanding how levonorgestrel works explains why it poses no risk to established pregnancy:
- Primary mechanism: Prevents or delays ovulation before the preovulatory LH surge 3, 4, 5
- Secondary mechanism: May inhibit sperm migration and affect fertilization 5
- All mechanisms occur before implantation—the medication has no effect on an implanted embryo 3, 6
Critical Evidence on Post-Ovulation Use
Research demonstrates that levonorgestrel emergency contraception has little to no effect on post-ovulation events:
- In a pilot study, all three pregnancies that occurred happened when women took the medication after ovulation had already occurred (Days +1 to +2) 6
- Among women who took levonorgestrel before ovulation, zero pregnancies occurred despite four being expected 6
- This strongly supports that levonorgestrel does not prevent implantation or disrupt early pregnancy 6
Clinical Implications
When Pregnancy Testing Is Needed
While levonorgestrel is safe if pregnancy exists, testing may be warranted in specific scenarios:
- If the next menstrual period is delayed by more than one week, pregnancy testing should be performed 2
- Severe abdominal pain after taking levonorgestrel requires immediate evaluation to rule out ectopic pregnancy 2
Common Pitfalls to Avoid
- Do not withhold levonorgestrel from women who are unsure of pregnancy status—the medication causes no harm even if pregnancy exists 1
- Do not confuse emergency contraception with medical abortion—levonorgestrel prevents pregnancy from starting; it does not disrupt established pregnancy 3
- Counsel patients that bleeding pattern changes do not indicate pregnancy or contraceptive failure—these are expected side effects 2
Bottom Line for Clinical Practice
Levonorgestrel emergency contraception should be provided without pregnancy testing when requested within 72 hours of unprotected intercourse, as the benefits of timely administration far outweigh any theoretical concerns, and no harm occurs if the patient is already pregnant. 1, 2, 3