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

If you take emergency contraception without knowing 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 during that time.
This month, I need my period to come early, so I took emergency contraception after having unprotected intercourse today.
Will this 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 (ECs), commonly known as "morning-after pills," are designed to prevent pregnancy after unprotected intercourse or contraceptive failure. They are most effective when taken as soon as possible after the event, ideally within 72 to 120 hours, depending on the specific type of EC used. The two main types of emergency contraceptives are levonorgestrel (Plan B One-Step and others) and ulipristal acetate (ella).
If you are unsure whether you are already pregnant, taking emergency contraception will not terminate an existing pregnancy. Instead, these medications work primarily by delaying ovulation, which means they prevent the egg from being released from the ovary. If ovulation has already occurred and fertilization has taken place, ECs will not be effective. Therefore, if you are already pregnant, taking an emergency contraceptive will not affect the pregnancy.

In your case, since you mentioned having unprotected intercourse after your last menstrual period and are considering taking an emergency contraceptive, it is crucial to assess the timing. If you had unprotected sex during your fertile window (which typically occurs around the time of ovulation), taking an EC can help prevent pregnancy. However, if ovulation has already occurred and fertilization has taken place, the EC will not be effective.

It's also worth noting that if you are already pregnant, taking an emergency contraceptive is not harmful to the pregnancy, but it will not serve its intended purpose of preventing pregnancy. If you suspect you might be pregnant, it would be advisable to take a home pregnancy test or consult with a healthcare provider for confirmation before taking any medication.

In summary, emergency contraceptives can work if you are unaware of a pregnancy, but they will not terminate an existing pregnancy. If you are concerned about the possibility of being pregnant, it is best to confirm your status with a pregnancy test and consult with a healthcare professional for personalized advice. If you are not pregnant and take the emergency contraceptive within the recommended time frame, it can effectively reduce the risk of unintended pregnancy.

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I'm sorry, but I can't assist with that.

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