Can Pre-Exposure Birth Control Pills Lead to Pregnancy?

Can emergency contraceptive pills cause pregnancy?

Doctor, I have been consistently taking the oral contraceptive pill, Yaz, but for the past two days, I have been taking medication for a urinary tract infection.
From January 27 to January 29, I had multiple sexual encounters, with only one instance of ejaculation inside and the rest being external ejaculation.
Is there a possibility of pregnancy in this situation?

Niming, 20~29 year old female. Ask Date: 2019/01/30

Dr. Cao Guotao reply Obstetrics and Gynecology

Hello, if you start taking birth control pills on the fifth day of your menstrual period and take them consistently, they will be effective in preventing pregnancy, making the likelihood of conception very low.
Wishing you good health!

Reply Date: 2019/01/30

More Info

When it comes to the effectiveness of pre-exposure birth control pills, such as Yaz (the brand name for the contraceptive pill you mentioned), it is important to understand how these medications work and the factors that can influence their efficacy. Birth control pills are designed to prevent ovulation, thicken cervical mucus to block sperm, and thin the uterine lining to prevent implantation. When taken consistently and correctly, they are highly effective, with a failure rate of less than 1% per year.

In your case, you mentioned that you have been taking Yaz regularly and that you also took medication for a urinary tract infection (UTI) during the same time frame. It is crucial to note that certain medications can potentially interact with birth control pills, affecting their effectiveness. For instance, some antibiotics, like rifampin, can reduce the effectiveness of hormonal contraceptives. However, most common antibiotics do not have this effect. If the medication you took for your UTI is not known to interact with hormonal contraceptives, your birth control should still be effective.

You also mentioned having multiple sexual encounters, with only one instance of ejaculation inside the vagina and the rest being withdrawal (pull-out method). The withdrawal method is not a reliable form of contraception, as pre-ejaculate fluid can contain sperm, and it requires perfect timing and control, which can be difficult to achieve. However, since you are on Yaz and have been taking it consistently, the likelihood of pregnancy is significantly reduced.

To summarize, if you have been taking your birth control pills as prescribed and the medication for your UTI does not interact with them, the chances of becoming pregnant are quite low, even with the one instance of internal ejaculation. However, if you are concerned about the possibility of pregnancy, it may be wise to take a home pregnancy test if your period is late or if you experience any unusual symptoms.

In addition to this, it is always a good idea to consult with your healthcare provider regarding any medications you are taking and their potential interactions with your birth control. They can provide personalized advice based on your medical history and the specific medications involved. If you have any doubts or concerns about your contraceptive method or potential pregnancy, do not hesitate to reach out to your healthcare provider for further guidance.

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