Emergency Contraceptive Pills: Effectiveness and Usage - Obstetrics and Gynecology

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Regarding oral emergency contraceptive pills?


Hello, doctor.
I would like to ask you about my situation.
I had unprotected sexual intercourse twice on February 26, once at 3 AM and again at 10 AM.
My last menstrual period started on February 7.
On March 1, I took two pills of emergency contraception.
Will these two instances of intercourse increase the likelihood of pregnancy? Currently, I only feel somewhat anxious and have no other symptoms.
Is the medication being absorbed properly? What is the effectiveness of the drug? (I purchased Postday brand while abroad; what is its efficacy?) If this medication is not effective, what other options do I have for emergency contraception? I am currently alone in South America and would like to avoid complications.
I would appreciate your advice and assistance!
I have researched that the dosage of mifepristone, used as an emergency contraceptive, is very small, requiring only 25 mg per dose.
For women who are already pregnant, a single oral dose of 25 mg mifepristone does not induce abortion.
The components can affect the development of the endometrium and its integrity, causing a temporary change in the environment necessary for the fertilized egg to survive, preventing implantation in the uterus.
It can also delay ovarian ovulation, causing a mismatch between ovulation and the development of the endometrium, thus achieving the purpose of emergency contraception and preventing unintended pregnancy.
Mifepristone (Postday) has a half-life of 26 hours and is rapidly absorbed, reaching peak plasma concentration within 15 minutes to 2 hours after ingestion, maintaining a prolonged therapeutic concentration.
A single dose taken within 72 hours after unprotected intercourse can effectively prevent pregnancy, with a failure rate of less than 1%.

leah, 20~29 year old female. Ask Date: 2011/03/03

Dr. Zhang Kunmin reply Obstetrics and Gynecology


Hello, the effectiveness of emergency contraceptive pills is 97% within 72 hours, but there is a difference in effectiveness between 24 hours and 72 hours.
This is a matter of probability and also depends on individual physiology.
If your period is late, it is best to undergo relevant examinations.
Thank you! Dr.
Chang

Reply Date: 2011/03/03

More Info


Emergency contraceptive pills (ECPs) are a crucial option for preventing unintended pregnancies after unprotected intercourse. In your case, you had two instances of unprotected sex on February 26, and you took two pills of the emergency contraceptive, Postday, on March 1. Let’s break down your concerns regarding the effectiveness, usage, and potential outcomes of this situation.


Effectiveness of Emergency Contraceptive Pills
ECPs, such as Postday, are most effective when taken as soon as possible after unprotected intercourse. They work primarily by delaying ovulation, which means they prevent the ovaries from releasing an egg. If taken within 72 hours after unprotected sex, ECPs can reduce the risk of pregnancy by up to 89%. However, their effectiveness decreases the longer you wait after intercourse. Since you took the pills approximately 48 hours after the last instance of unprotected sex, you are within the effective window.


Impact of Multiple Intercourse Events
Regarding your question about whether having two instances of unprotected sex increases the likelihood of pregnancy, it is important to note that the risk of pregnancy is based on whether ovulation has occurred. If you had unprotected sex before ovulation, the risk of pregnancy is higher. However, since you took the ECPs, they should help mitigate that risk. The timing of your menstrual cycle is also relevant; since your last period started on February 7, you were likely approaching ovulation around the time of your unprotected intercourse, which typically occurs around 14 days before your next expected period.


Absorption and Efficacy of the Medication
You mentioned concerns about whether the medication has been absorbed and its efficacy. Postday, like other ECPs, is rapidly absorbed in the gastrointestinal tract. Most women will experience peak blood levels of the active ingredients within 1 to 2 hours after ingestion. If you took the pills as directed, they should have been absorbed effectively. The common side effects of ECPs include nausea, fatigue, and changes in your menstrual cycle, but these do not indicate whether the medication has worked.


Alternative Options if ECPs Fail
If you are concerned about the effectiveness of the ECPs, it is important to monitor your body for any signs of pregnancy, such as a missed period or unusual symptoms. If your period is delayed by more than a week, you should take a pregnancy test. If the test is positive, you may want to consult a healthcare provider for further options.

In terms of additional measures, there are no other emergency contraceptive methods that can be taken after ECPs. If you are looking for ongoing contraception, consider discussing long-term options with a healthcare provider once you return home or have access to medical services.


Conclusion
In summary, taking Postday within the recommended timeframe after unprotected intercourse should significantly reduce your risk of pregnancy. While having multiple instances of unprotected sex can increase the risk, the timely administration of ECPs is designed to prevent pregnancy effectively. Monitor your menstrual cycle closely, and if you have any concerns or experience unusual symptoms, seek medical advice promptly. Remember, it’s always best to consult with a healthcare professional for personalized guidance, especially when you are in a foreign country.

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