Contraceptive Pills: Risks of Unprotected Sex After 12 Days

This is the first time asking my girlfriend to take emergency contraceptive pills?

If my girlfriend has been taking birth control pills for 12 days and we had unprotected intercourse on the 12th day, could she become pregnant? She started taking the pills on the first day of her menstrual cycle and even if she forgot, she took them 1 to 2 hours late, but she takes them at the same time every day.
Given that her menstrual cycle is usually around 40 days and this is her first time taking the pills, what is the likelihood of her becoming pregnant?

Mr. Wu, 10~19 year old female. Ask Date: 2016/01/11

Dr. Lin Wenbin reply Obstetrics and Gynecology

The effectiveness of contraception is lower during the first month of use, while it improves after the second month.
It is advisable to use condoms in addition to contraception during the first month for safer pregnancy prevention.

Reply Date: 2016/01/11

More Info

When it comes to understanding the risks of pregnancy after engaging in unprotected sex while on contraceptive pills, it's essential to consider several factors, including the timing of the pill intake, the consistency of usage, and the individual's menstrual cycle.

In your case, your girlfriend has been taking the contraceptive pill for 12 days, starting from the first day of her menstrual cycle. This is a crucial point because most hormonal contraceptives are designed to be effective after a certain period of consistent use. Generally, if taken correctly, most combination birth control pills become effective after seven consecutive days of use. Since your girlfriend has been taking the pill consistently, even if she has missed a dose by 1-2 hours, her contraceptive effectiveness should remain intact.

Given that she has been on the pill for 12 days and has taken it regularly, the likelihood of pregnancy from unprotected intercourse on the 12th day is quite low. The effectiveness of the pill is typically around 91-99% when taken correctly, which means that while there is still a small chance of failure (around 1-9%), it is significantly reduced compared to not using any form of contraception.

However, it is important to note that individual factors can influence the effectiveness of the pill. For instance, if your girlfriend has experienced any gastrointestinal issues (like vomiting or diarrhea) shortly after taking the pill, this could affect its absorption and efficacy. Additionally, certain medications, such as some antibiotics or anti-seizure medications, can also reduce the effectiveness of hormonal contraceptives.

Regarding her menstrual cycle, you mentioned that her cycles are typically around 40 days. This is longer than the average cycle, which is usually between 21 to 35 days. A longer cycle can sometimes indicate irregular ovulation, which may affect the timing of when she is most fertile. However, since she is on the pill, it is designed to regulate her cycle and suppress ovulation, making it less likely for her to conceive during this time.

In summary, based on the information provided, the risk of pregnancy after having unprotected sex on the 12th day of consistent contraceptive pill use is low. However, if there are any concerns about missed pills or other factors that could affect the pill's effectiveness, it is advisable to consult with a healthcare provider. They can provide personalized advice and may suggest taking a pregnancy test if her period is late or if there are any unusual symptoms.
Lastly, it’s always a good practice to use additional protection, such as condoms, especially during the first month of starting a new contraceptive method or if there are any doubts about the pill's effectiveness. This not only helps prevent pregnancy but also protects against sexually transmitted infections (STIs).

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