Emergency Contraceptive Pills: Effectiveness and Menstrual Cycle Insights

Questions related to the use of emergency contraceptive pills and menstrual periods?

Hello Doctor, on April 7th, the condom accidentally slipped off, and I clearly felt ejaculation inside, with some fluid leaking out.
Within an hour after the incident, I took the emergency contraceptive pill.
However, after researching, I found many sources stating that taking emergency contraception after ovulation will be ineffective.
According to the menstrual cycle calculator, my ovulation period was on March 22, and my expected menstruation is between April 6 and April 16.
I would like to know if taking the emergency contraceptive pill in this situation is effective.
How can I know if it has worked? If my period arrives as scheduled, does that mean the contraception was successful? I appreciate your time in answering these questions.
Thank you.

Chen, 20~29 year old female. Ask Date: 2023/04/07

Dr. Zhang Kunmin reply Obstetrics and Gynecology

Hello, the effectiveness of emergency contraceptive pills is not 100%, with a failure rate of about 3%.
Emergency contraceptive pills primarily work by delaying or inhibiting ovulation to prevent the sperm and egg from meeting.
They may also alter cervical mucus to reduce the likelihood of fertilization.
Sperm can survive in the female body for up to 5 days, but they are most fertile in the first 2 days.
After ovulation, the egg can survive for a maximum of 24 hours.
If the medication is taken before ovulation occurs, it can delay the release of the egg, and by that time, the sperm may no longer be viable, thus achieving contraceptive effects.
If ovulation has already occurred and more than 24 hours have passed, the egg is likely dead, so theoretically, it wouldn't matter whether the emergency contraceptive was taken or not, but it may still yield an "effective" result.
If the body signals ovulation (LH surge) just before taking the emergency contraceptive, the medication may be ineffective.
In such circumstances, this potential life may be destined to be born.
In clinical practice, since the timing of ovulation is difficult to confirm, it is recommended to use emergency contraceptive pills if unprotected intercourse has occurred and pregnancy is not desired.
If menstruation is more than a week late, it is advisable to check for pregnancy.
Thank you! Wishing you peace and health.
Dr.
Zhang

Reply Date: 2023/04/07

More Info

Emergency contraceptive pills (ECPs) are designed to prevent pregnancy after unprotected intercourse or contraceptive failure, such as a broken condom. The effectiveness of ECPs, such as Plan B (levonorgestrel) or Ella (ulipristal acetate), depends on several factors, including the timing of administration relative to the menstrual cycle and ovulation.

In your case, you mentioned that the incident occurred on April 7, and you took the emergency contraceptive pill within an hour. This is a crucial factor because ECPs are most effective when taken as soon as possible after unprotected intercourse. Levonorgestrel is most effective when taken within 72 hours, while ulipristal acetate can be effective up to 120 hours after intercourse. Since you took the pill promptly, you maximized your chances of preventing pregnancy.

Regarding your ovulation cycle, you indicated that your ovulation was around March 22, with your expected menstruation between April 6 and April 16. If you ovulated on March 22, the egg would typically be viable for fertilization for about 12 to 24 hours. Sperm can live inside the female reproductive tract for up to five days. Therefore, if you had unprotected intercourse on April 7, it would be outside the window of fertility for that cycle, assuming you ovulated as expected.
However, it is important to note that menstrual cycles can vary, and ovulation can sometimes occur later than anticipated. If you are concerned about the effectiveness of the ECP, you can take a pregnancy test if your period is delayed by more than a week after your expected date. If your period arrives as scheduled, it is generally a good indication that the ECP was effective in preventing pregnancy.

In summary, taking the emergency contraceptive pill shortly after the incident increases the likelihood of preventing pregnancy. If your period arrives on time, it is a strong indication that you are not pregnant. If you have any further concerns or experience unusual symptoms, it is advisable to consult with a healthcare provider for personalized advice and support.
Additionally, it is important to remember that ECPs are not intended for regular contraceptive use and do not protect against sexually transmitted infections (STIs). If you find yourself needing emergency contraception frequently, consider discussing long-term contraceptive options with your healthcare provider to find a method that suits your needs and lifestyle.

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