Emergency Contraception: Success Rates and Menstrual Cycle Insights

Emergency contraception and preemptive contraception, and whether they are effective in preventing pregnancy?

Hello Doctor, my menstrual cycle has been irregular.
In the past three months, my periods were as follows: October 27 to November 2, December 11 to December 17, and January 16 to January 22.
I had sexual intercourse on January 24 (the second day after my period ended) and I am unsure if the condom was used properly (there was no ejaculation).
The next day, around 12-1 PM, I took emergency contraception.
However, I had sexual intercourse again on January 26 (the fourth day after my period ended), and this time I checked the condom for leaks and it was intact!
After taking the emergency contraception, I experienced bleeding on the sixth day, which was similar in volume to my regular menstrual flow and lasted about four days.
On the fifth day, the blood was a dark brown color, and on the sixth and seventh days (today), there was no bleeding at all.
I consulted a pharmacist who said that any bleeding indicates that it is a menstrual period.
Is this correct, Doctor?
Yesterday, I took a pregnancy test for the first time on the 12th day after the intercourse, and again on the 10th and 18th days.
I saw one line, which reassured me a lot.
However, today, February 24, I noticed a little bit of blood when I wiped after using the restroom (it's very minimal, and I'm still observing it).
If this is normal bleeding, could you please tell me if that instance was my period? Does this mean that I successfully prevented pregnancy? Is it normal to have two periods in one month? If I want to start taking preemptive contraception, should I begin taking it from the fifth day of my cycle? Thank you, Doctor.

Yú bǐng, 20~29 year old female. Ask Date: 2023/02/24

Dr. Cao Guotao reply Obstetrics and Gynecology

Hello, you are likely not pregnant.
Emergency contraception can sometimes cause irregular menstruation.
Regular birth control pills should be started on the fifth day of your menstrual cycle.
Wishing you good health.

Reply Date: 2023/02/24

More Info

Emergency contraception (EC) is a crucial option for individuals who have had unprotected intercourse or contraceptive failure. Understanding its success rates and how it interacts with the menstrual cycle is essential for informed decision-making.

Success Rates of Emergency Contraception
Emergency contraception methods, such as levonorgestrel (Plan B) and ulipristal acetate (Ella), are most effective when taken as soon as possible after unprotected intercourse. Levonorgestrel is effective up to 72 hours after intercourse, while ulipristal acetate can be effective up to 120 hours. The success rates vary depending on the timing of administration relative to ovulation.
- Levonorgestrel: When taken within 72 hours, it can reduce the risk of pregnancy by 75-89%. Its effectiveness decreases the longer you wait after unprotected intercourse.

- Ulipristal Acetate: This method maintains its effectiveness throughout the 120-hour window, with a similar success rate to levonorgestrel when taken early.

Menstrual Cycle Insights
Your menstrual cycle plays a significant role in determining the effectiveness of emergency contraception. The cycle can be divided into phases: the follicular phase, ovulation, and the luteal phase. Ovulation typically occurs around the midpoint of the cycle, and this is when a woman is most fertile.
Given your reported cycle irregularities, it’s essential to note that ovulation can vary significantly. If you had unprotected intercourse shortly after your period, it is less likely that you were ovulating, which may reduce the risk of pregnancy. However, sperm can survive in the female reproductive tract for up to five days, so if you ovulate shortly after the unprotected intercourse, there is still a risk of pregnancy.

Interpretation of Your Situation
You mentioned taking emergency contraception the day after unprotected intercourse and experiencing bleeding that resembled your typical menstrual flow. This bleeding could be a side effect of the emergency contraception, often referred to as withdrawal bleeding, which can occur due to hormonal changes induced by the medication.
The bleeding you experienced six days after taking the emergency contraception could indeed be your period or withdrawal bleeding. If it lasted about four days and had a similar flow to your usual menstruation, it is likely that it was your period.

Pregnancy Testing
You conducted pregnancy tests at various intervals, and the results indicated no pregnancy (one line). This is reassuring, especially if the tests were taken after the expected time of your period. However, if you continue to experience unusual bleeding or other symptoms, it may be wise to consult a healthcare provider for further evaluation.

Future Contraceptive Use
If you are considering starting a regular contraceptive method, it is generally advised to begin taking hormonal contraceptives (like birth control pills) at least five days after the start of your next menstrual period to ensure that you are not pregnant. This timing helps to ensure that the contraceptive is effective immediately.

Conclusion
In summary, based on your description, it appears that the emergency contraception was effective, and the bleeding you experienced could be your menstrual period. If you have further concerns or if your menstrual cycle continues to be irregular, it would be beneficial to consult with a healthcare provider. They can provide personalized advice and discuss long-term contraceptive options that may better suit your needs.

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