Effectiveness of Birth Control Pills During Fertile Window: What You Need to Know

I have been taking birth control pills for three months, and after having sexual intercourse, I realized I was in the fertile window?

Hello, Doctor: I have been taking oral contraceptives for three months now.
After having sexual intercourse today, I realized that I did not use a condom for additional contraception and checked the calculations for the fertile period, discovering that I am currently in the high-risk period.
I would like to ask if the oral contraceptive is still effective during this high-risk period, and whether I can also take emergency contraception as an additional method of contraception.

Li, 20~29 year old female. Ask Date: 2016/01/09

Dr. Tian Yiwen reply Obstetrics and Gynecology

If taken regularly, oral contraceptives theoretically reduce the chance of pregnancy significantly because they suppress ovulation.
Without ovulation, there is no so-called fertile window, and thus no risk of pregnancy, which is why emergency contraception is usually not necessary.
However, it is still recommended to use condoms during sexual intercourse, both as a secondary method of contraception to enhance effectiveness and, more importantly, to prevent the transmission of sexually transmitted infections.

Reply Date: 2016/01/09

More Info

When it comes to the effectiveness of birth control pills during the fertile window, it's important to understand how these medications work and what factors can influence their efficacy. Birth control pills, when taken correctly, are highly effective in preventing pregnancy, with a typical use effectiveness rate of about 91% to 99%. This means that while they are very reliable, there is still a small chance of pregnancy, especially if the pills are not taken consistently or as directed.

The "fertile window" refers to the days in a woman's menstrual cycle when she is most likely to conceive. This typically includes the days leading up to and including ovulation. For women using hormonal birth control pills, the hormones in the pills work to prevent ovulation, meaning that if the pills are taken correctly, ovulation should not occur, and thus, the chances of becoming pregnant are significantly reduced.

However, if you have been taking your birth control pills for only three months, it's crucial to ensure that you are taking them consistently and at the same time every day. If you missed any doses or did not take them as prescribed, the effectiveness could be compromised, especially during your fertile window. In such cases, the risk of pregnancy increases.

Regarding your question about taking emergency contraception (the "morning-after pill") after having unprotected sex during your fertile window, it is indeed an option. Emergency contraception can be used to prevent pregnancy after unprotected intercourse, and it is most effective when taken as soon as possible after the event. There are two main types of emergency contraception: the levonorgestrel pill (Plan B) and ulipristal acetate (Ella). Both are effective, but ulipristal acetate can be taken up to 120 hours after unprotected sex and may be more effective during the fertile window.

It's important to note that while taking emergency contraception can provide an additional layer of protection, it should not be used as a regular form of birth control. It is designed for occasional use and is less effective than regular contraceptive methods. Additionally, using emergency contraception does not replace the need for regular birth control methods, and it is advisable to continue taking your birth control pills as prescribed.

In summary, if you have been taking your birth control pills consistently and correctly, they should still be effective even during your fertile window. However, if you are concerned about potential pregnancy due to unprotected sex, taking emergency contraception can be a prudent choice. Always consult with your healthcare provider for personalized advice and to discuss any concerns you may have regarding your birth control method and sexual health. They can provide you with the most accurate information tailored to your specific situation.

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