Menstrual Changes After Taking Emergency Contraceptive Pills

After taking emergency contraception, when will the next menstrual period occur?

Hello, doctor.
I would like to ask about my menstrual cycle from July 14 to July 18.
I had sexual intercourse from July 16 to July 18 with protection, but on July 18, there was one instance without a condom, and I had external ejaculation.
Later, I was worried and took emergency contraception that same day.
After taking the emergency contraception, I experienced bleeding on July 24, which I believe is related to the emergency contraceptive.
I had sexual intercourse again from August 12 to August 14, and all instances were protected.
I would like to know if the irregular bleeding caused by the emergency contraception means I should calculate my menstrual cycle starting from the bleeding on July 24 or from the period on July 14.
It is now August 23, and I am a bit concerned that my period has not arrived.
Additionally, if I am taking antibiotics for a urinary tract infection (the orange capsule), can I take them together with my regular birth control pills? Thank you!

Niming, 20~29 year old female. Ask Date: 2018/08/23

Dr. Huang Jianzhong reply Obstetrics and Gynecology

1.
You should calculate your menstrual cycle starting from the bleeding on July 24, as it is likely related to the emergency contraceptive pill you took.
The amount of bleeding and the thickness of the endometrium will help determine if this was a withdrawal bleed or an actual menstrual period.
Since today is August 23 and your period has not arrived, it is understandable to be concerned.
2.
It is better to take antibiotics for urinary tract infections (the orange capsule) separately from your regular birth control pills to avoid any potential interactions.

Reply Date: 2018/08/23

More Info

Understanding menstrual changes after taking emergency contraceptive pills (ECPs) can be quite complex, as various factors can influence the menstrual cycle. In your case, you experienced a series of events that could lead to confusion regarding your menstrual cycle and the effects of the emergency contraceptive pill.

First, it's important to clarify how ECPs work. Emergency contraceptive pills, such as Plan B (levonorgestrel) or Ella (ulipristal acetate), are designed to prevent pregnancy after unprotected intercourse. They primarily work by delaying ovulation, preventing fertilization, or preventing a fertilized egg from implanting in the uterus. However, they can also cause temporary changes in your menstrual cycle.

In your situation, you had your menstrual period from July 14 to July 18, and after an incident of unprotected intercourse on July 18, you took an emergency contraceptive pill the same day. The bleeding you experienced on July 24 is likely a side effect of the ECP, which can cause what is known as "withdrawal bleeding." This bleeding can be lighter or different from your usual menstrual period, and it may not be a true menstrual cycle.

To answer your question about when to start counting your cycle: Typically, the first day of your menstrual period is considered Day 1 of your cycle. However, since you experienced withdrawal bleeding on July 24 after taking the ECP, you could consider that as the start of a new cycle. Therefore, if you are counting from July 24, you would expect your next period approximately 28 days later, which would be around August 21. Since you mentioned that it is now August 23 and your period has not arrived, it is understandable to feel concerned.

Regarding the use of antibiotics for a urinary tract infection (UTI), it is generally safe to take antibiotics while on birth control pills, including emergency contraceptives. However, some antibiotics can potentially reduce the effectiveness of hormonal contraceptives. It is essential to consult with your healthcare provider about the specific antibiotic you are taking to ensure that it does not interfere with your birth control method.

In summary, the bleeding you experienced on July 24 could be attributed to the emergency contraceptive pill, and you may consider that as the start of a new cycle. Since your period has not arrived by August 23, it would be advisable to take a pregnancy test to rule out pregnancy, especially since you had unprotected intercourse. If you have further concerns or if your period does not arrive soon, it is best to consult with your healthcare provider for personalized advice and guidance. They can help you understand your situation better and address any underlying issues related to your menstrual cycle and contraceptive use.

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