Can Emergency Contraceptives Work If You're Unaware of Pregnancy?

If you take emergency contraception without knowing if you are pregnant, is it effective?

I would like to ask if I am unsure whether I am pregnant.
My last menstrual period ended between the 15th and 20th of last month, and I had several instances of ejaculation inside.
This month, I need my period to come early.
If I take emergency contraception today, will it prevent pregnancy this time? If I am already pregnant, will taking the emergency contraception be ineffective?

Y, 20~29 year old female. Ask Date: 2024/07/07

Dr. Zhang Kunmin reply Obstetrics and Gynecology

Hello, the effectiveness of emergency contraceptive pills is not 100%.
The failure rate is about 3% if taken within three days.
If taken after three days, the contraceptive effect is insufficient.
It is recommended to check for pregnancy if your period is more than a week late.
Thank you! Wishing you peace and health.
Dr.
Chang

Reply Date: 2024/07/07

More Info

Emergency contraceptives (EC), commonly known as "morning-after pills," are designed to prevent pregnancy after unprotected intercourse or contraceptive failure. They work primarily by delaying ovulation, preventing fertilization, or inhibiting implantation of a fertilized egg. However, their effectiveness is contingent upon the timing of administration relative to the menstrual cycle and the timing of ovulation.

If you are unsure whether you are already pregnant, taking emergency contraception is generally still recommended if you have had unprotected intercourse. However, it is crucial to understand that emergency contraceptives are not effective if a pregnancy has already been established. If you are already pregnant, taking EC will not terminate the pregnancy or harm the fetus, as these medications do not have abortifacient properties. They are not designed to disrupt an existing pregnancy.

In your case, since you mentioned that you had unprotected intercourse after your last menstrual period and are concerned about the possibility of being pregnant, taking emergency contraception as soon as possible is advisable. The sooner you take it after unprotected intercourse, the more effective it will be. For instance, levonorgestrel (Plan B One-Step) is most effective when taken within 72 hours, while ulipristal acetate (Ella) can be effective up to 120 hours after intercourse.

It's also important to note that if you are experiencing any unusual symptoms or have concerns about a possible pregnancy, it would be prudent to take a pregnancy test. If the test is negative and you take the emergency contraceptive, you can proceed with your plans without worry. If the test is positive, you should consult with a healthcare provider to discuss your options moving forward.

In summary, if you are uncertain about being pregnant and have had unprotected intercourse, taking emergency contraception is a reasonable step. However, if you are already pregnant, the emergency contraceptive will not be effective, but it will not harm the pregnancy either. Always consult with a healthcare professional for personalized advice and to discuss any concerns you may have regarding your reproductive health.

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