Pregnancy Chances After Contraceptive Use and Antibiotics

Probability of Pregnancy

I started taking the contraceptive pill on the first day of my period on July 10.
However, on July 16, I developed a stye and was prescribed a three-day course of medication containing cephalexin (while continuing to take the contraceptive pill).
Then, on July 22, I had unprotected intercourse (withdrawal method).
What is the likelihood of becoming pregnant in this situation?

Youyou, 20~29 year old female. Ask Date: 2020/08/02

Dr. Cao Guotao reply Obstetrics and Gynecology

Hello, continuing to take contraceptive pills will provide contraceptive effectiveness.
Wishing you good health.

Reply Date: 2020/08/02

More Info

When considering the chances of pregnancy after using contraceptives and antibiotics, it is essential to understand how these factors interact. In your case, you began taking the contraceptive pill (Yaz) on July 10, and while continuing to take it, you were prescribed cephalexin for a stye on July 16. You then had unprotected intercourse on July 22.
First, it's important to note that most hormonal contraceptives, like Yaz, are highly effective when taken correctly. The effectiveness of these pills is around 91-99% with typical use, meaning that while there is still a small chance of pregnancy, it is significantly reduced when the pills are taken consistently and correctly.
Regarding the use of antibiotics, there is a common concern that certain antibiotics can interfere with the effectiveness of hormonal contraceptives. However, cephalexin is generally not known to significantly affect the efficacy of birth control pills. The only antibiotics that have been shown to potentially reduce the effectiveness of hormonal contraceptives are rifampin and rifabutin, which are used to treat tuberculosis and certain other infections. Therefore, taking cephalexin while on Yaz should not have compromised your contraceptive protection.

Given that you were actively taking your contraceptive pill during the time you were prescribed cephalexin and continued to take it correctly, the likelihood of pregnancy from the unprotected intercourse on July 22 is low. However, no contraceptive method is 100% effective, and there is always a small risk of pregnancy with any method of contraception.

If you are concerned about the possibility of pregnancy, the best course of action is to wait until your next expected period. If your period is late, you should take a home pregnancy test for confirmation. If you have any further concerns or experience any unusual symptoms, it would be advisable to consult with your healthcare provider for personalized advice and guidance.

In summary, while there is always a small chance of pregnancy with any contraceptive method, the combination of taking Yaz correctly and the use of cephalexin should not significantly increase your risk. If you have further questions or concerns about your contraceptive method or the use of antibiotics, discussing them with your healthcare provider can provide you with the most accurate and tailored information.

Similar Q&A

Understanding Pregnancy Risks After Contraceptive Use and Antibiotics

I started taking the contraceptive pill on the first day of my period on July 10. However, on July 16, I developed a stye and was prescribed a three-day course of medication containing cephalexin (while continuing to take the contraceptive pill). Then, on July 22, I had unprotect...

Dr. Huang Yuande reply Obstetrics and Gynecology
If contraceptive pills are taken continuously, the chances of becoming pregnant are very low, and this is unrelated to the use of antibiotics. Thank you for your question.

Understanding Pregnancy Chances After Antibiotics and Emergency Contraception

At the end of July, I underwent surgery and took antibiotics, which caused my menstrual cycle to change to 38 days. My menstrual bleeding in August lasted for 7 days (from August 28 to September 3). I took antibiotics on September 8 and finished them on September 15, after which ...

Dr. Cao Guotao reply Obstetrics and Gynecology
Hello, the chances of pregnancy should be low. Just observe for now. Wishing you good health.

Understanding Interactions of Emergency Contraceptives and Antibiotics

I have already taken the fifth pack from June 30 to July 20, the first pack from July 28 to August 17, the second pack from August 25 to September 14, the third pack from September 22 to October 12, and the fourth pack starting October 20. However, from the evening of October 11 ...

Dr. Cao Guotao reply Obstetrics and Gynecology
Hello, antibiotics do not affect the effectiveness of birth control pills, so if you are taking contraceptives, you should not become pregnant. Wishing you good health.

Can Antibiotics Affect Birth Control Effectiveness? Your Questions Answered

Hello Dr. Tsao, I have been taking the contraceptive pill "Yueji" for four months, and I have been taking it on time. However, on December 31, I had a toothache and underwent a root canal treatment, during which my dentist prescribed antibiotics for me. I took one antib...

Dr. Cao Guotao reply Obstetrics and Gynecology
Hello, you can start taking the contraceptive pill on the fifth day of your menstrual period. It doesn't have to be taken at the exact same time; a rough timeframe is sufficient. As long as you take it regularly, it will be effective for contraception. If you forget to take ...