Is the Morning After Pill Abortive?
No, emergency contraception pills (levonorgestrel and ulipristal acetate) are not abortive medications—they work by preventing or delaying ovulation before fertilization occurs, and they do not terminate an established pregnancy. 1
Mechanism of Action
How Emergency Contraception Works
- Levonorgestrel prevents pregnancy primarily by inhibiting or delaying ovulation when taken at least 2 days before ovulation occurs. 2
- If ovulation is imminent or has already occurred, levonorgestrel is no longer effective because it cannot prevent fertilization. 2
- Ulipristal acetate can delay ovulation even when taken 24-48 hours before expected ovulation, during the advanced follicular phase when LH levels have begun to rise—a time when levonorgestrel no longer works. 3, 4
- Research demonstrates no biological data supporting the view that levonorgestrel impairs embryo development or prevents implantation. 2
What Happens If Already Pregnant
- The CDC explicitly states that emergency contraceptive pills cause no harm to the woman, the course of her pregnancy, or the fetus if inadvertently used during an established pregnancy. 1
- Emergency contraception is classified as "not applicable" for pregnancy because the method is not indicated for known or suspected pregnancy, but poses no risk if accidentally taken. 1
Clinical Evidence on Timing and Effectiveness
Why Timing Matters
- The clinical observation that pregnancy risk increases with greater intervals between intercourse and emergency contraception administration supports that the mechanism is prevention of fertilization, not disruption of implantation. 2
- Emergency contraception prevents approximately 50-80% of pregnancies, with effectiveness declining as the time from intercourse increases. 2
- Ulipristal acetate maintains effectiveness up to 5 days (120 hours) after unprotected intercourse, while levonorgestrel effectiveness significantly decreases after 72 hours. 3, 5
Comparison to Truly Abortive Methods
- In contrast to emergency contraceptive pills, other methods like mifepristone and intrauterine devices can inhibit implantation and may work after fertilization has occurred. 2
- This distinction is critical: levonorgestrel and ulipristal acetate work before fertilization, while mifepristone (the abortion pill) works after implantation. 2
Important Clinical Considerations
Safe Use in Special Populations
- Emergency contraception can be used safely in breastfeeding women, with levonorgestrel being Category 1 (no restrictions). 1
- The American College of Cardiology/American Heart Association guidelines note that levonorgestrel (the morning-after pill) is safe for women with congenital heart disease, though acute fluid retention is a risk to consider. 1
When to Use Emergency Contraception
- Emergency contraception should be used after unprotected intercourse, contraceptive failure, or missed/late doses of regular contraception. 6
- It can and should be used even when already on regular hormonal contraception if unprotected intercourse has occurred. 6
- The copper IUD is the most effective emergency contraception option when inserted within 5 days of unprotected intercourse, but oral methods are more commonly used. 7
Common Misconceptions to Address
Access to emergency contraception is often limited due to prevailing misconceptions about how it works, despite all methods being extremely safe. 7 The scientific evidence clearly demonstrates that levonorgestrel and ulipristal acetate prevent pregnancy by blocking ovulation before fertilization can occur, not by terminating an established pregnancy.