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Emergency Contraceptive, iPill - When it works and when it doesn't

Updated: Dec 16, 2023

Unplanned pregnancies can be a source of stress and uncertainty for many women. Fortunately, emergency contraceptive pills like the i-pill offer a safety net in such situations, helping to prevent unintended pregnancies. However, understanding how these pills work, their limitations, and when they may not be effective is crucial. In this blog, we will delve into the mechanics of emergency contraceptive pills, their effectiveness, and the situations in which they may not provide the desired outcome. We'll also discuss more sustainable long-term contraceptive options for women to consider.

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The Mechanism of Emergency Contraceptive Pills


Emergency contraceptive pills, like ipill, often referred to as morning-after pills or emergency contraception (EC), contain hormones that are designed to prevent pregnancy when taken after unprotected intercourse or contraceptive failure. There are two main types of emergency contraceptive pills: those containing levonorgestrel (Plan B One-Step, Take Action) and those containing ulipristal acetate (ella). Explore full time birth control options here.

  1. Levonorgestrel-based pills: Levonorgestrel is a synthetic hormone that works primarily by delaying or inhibiting ovulation, the release of an egg from the ovary. Additionally, it may alter the cervical mucus, making it more difficult for sperm to reach and fertilize an egg.

  2. Ulipristal acetate-based pills: Ella, a more recently developed emergency contraceptive, works similarly to levonorgestrel but is more effective at delaying ovulation. It may also have a direct effect on the uterine lining, reducing the chances of a fertilized egg implanting.


When Emergency Contraceptive Pills Are Effective


Emergency contraceptive pills are most effective when taken as soon as possible after unprotected intercourse or contraceptive failure. The sooner they are used, the higher the likelihood of preventing pregnancy. In general, they can be taken up to 72 hours (levonorgestrel) or 120 hours (ella) after unprotected sex.

However, it's essential to note that their efficacy diminishes over time. Ideally, the pills should be taken within the first 24 hours for the best results. The effectiveness rates are as follows:

  • Within 24 hours: Levonorgestrel-based pills are approximately 95% effective, while ulipristal acetate-based pills are around 98% effective.

  • Within 72 hours: Levonorgestrel-based pills are less effective, with a success rate of about 89%, whereas ulipristal acetate-based pills maintain their effectiveness at around 85%.

In summary, emergency contraceptive pills can be highly effective when used promptly after unprotected intercourse or contraceptive failure, but their success rate decreases as time passes.


When Emergency Contraceptive Pills May Not Work


While emergency contraceptive pills are a valuable tool for preventing unplanned pregnancies, there are circumstances in which they may not work as intended. One of the most critical factors affecting their efficacy is the timing of the woman's menstrual cycle, specifically ovulation.


Ovulation is the process where a mature egg is released from the ovary, and it is the most fertile time during a woman's cycle. Sperm can survive in the female reproductive tract for up to five days, so if a woman has unprotected intercourse during or shortly before ovulation, there is a higher likelihood of pregnancy even if emergency contraceptive pills are used.

Here are scenarios when emergency contraceptive pills may be less effective:

  1. Ovulation: If a woman has already ovulated or is about to ovulate when she takes the pill, there is a chance that the pill may not prevent pregnancy because it primarily works by delaying or inhibiting ovulation. Tracking ovulation can be challenging, but there are methods like calendar tracking, temperature charting, or ovulation predictor kits that can provide some guidance.

  2. Late usage: Waiting too long to take the pill reduces its effectiveness. The longer you wait, the higher the likelihood that the egg and sperm have already met, making fertilization possible. Always take the pill as soon as possible after unprotected intercourse.

  3. Multiple acts of intercourse: If there are multiple acts of intercourse over a short period, it can be challenging to determine the exact timing of ovulation, making it difficult to predict the pill's effectiveness.

  4. Obesity: Some studies suggest that emergency contraceptive pills may be less effective in women with a higher body mass index (BMI). This is an area where more research is needed, but it's a factor to consider.

The Best Uses of Emergency Contraceptive Pills


Emergency contraceptive pills are a valuable resource when used correctly and in the right circumstances. Here are some situations where they can be particularly helpful:

  1. Contraceptive failure: When a condom breaks, a diaphragm slips out of place, or another form of contraception fails, emergency contraceptive pills can provide an added layer of protection.

  2. Missed birth control pills: If you forget to take one or more birth control pills or are inconsistent with your birth control method, using emergency contraception can help reduce the risk of pregnancy.

  3. Sexual assault: In cases of sexual assault or forced intercourse, emergency contraceptive pills can be a crucial option for preventing an unplanned pregnancy.

  4. Unplanned encounters: Sometimes, spontaneous sexual encounters may occur without access to regular contraception. Emergency contraceptive pills offer a way to reduce the risk of pregnancy in such situations.

A More Sustainable Approach to Contraception


While emergency contraceptive pills are essential for preventing unintended pregnancies in certain situations, they are not a long-term solution to birth control. For ongoing contraception and greater peace of mind, women should consider more sustainable methods, such as:

  1. Regular birth control pills: These are taken daily to provide ongoing contraception. There are different types of birth control pills, so it's essential to consult with a healthcare provider to find the one that suits your needs best.

  2. Intrauterine Devices (IUDs): IUDs are highly effective and can provide contraception for several years. They come in hormonal and non-hormonal varieties, offering options for different preferences and medical considerations.

  3. Contraceptive implants: These are small rods inserted under the skin that release hormones to prevent pregnancy for several years.

  4. Condoms: Condoms not only provide protection against pregnancy but also offer protection against sexually transmitted infections (STIs). They are a good option for those who want dual protection. Find out more about condom usage here.



Emergency contraceptive pills, like the i-pill, can be a valuable tool in preventing unplanned pregnancies when used correctly and promptly. Understanding how they work and their limitations, especially in relation to ovulation, is crucial for their effective use. While they are a vital resource in certain situations, they are not a replacement for long-term contraception methods like birth control pills, IUDs, or implants, which offer greater reliability and peace of mind. Women should consult with healthcare providers to explore and choose the contraception method that aligns best with their individual needs and lifestyle, ensuring responsible family planning and reproductive health.
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