How Long is the Emergency Contraceptive Pill Effective After Taking It? - Obstetrics and Gynecology

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The emergency contraceptive pill (ECP), commonly referred to as the "morning-after pill," is designed to prevent pregnancy after unprotected intercourse or contraceptive failure. The effectiveness of the ECP depends on several factors, including the type of pill taken, the timing of ingestion relative to ovulation, and individual physiological differences.

There are two main types of emergency contraceptive pills: those containing levonorgestrel (such as Plan B One-Step) and those containing ulipristal acetate (such as Ella).
1. Levonorgestrel (Plan B One-Step): This type of ECP is most effective when taken within 72 hours (3 days) after unprotected sex. However, it can still be taken up to 5 days after intercourse, but its effectiveness diminishes significantly with each passing day. Studies indicate that it can reduce the risk of pregnancy by about 89% when taken within the recommended time frame. After 72 hours, the effectiveness drops, and it is not recommended as a reliable method of preventing pregnancy.

2. Ulipristal Acetate (Ella): This ECP can be taken up to 120 hours (5 days) after unprotected intercourse and maintains its effectiveness throughout this period. It works by delaying or inhibiting ovulation, and it is generally considered more effective than levonorgestrel, especially when taken later within the 5-day window.

It is important to note that while ECPs are effective at preventing pregnancy, they do not terminate an existing pregnancy. If a woman is already pregnant, taking an ECP will not have any effect on the pregnancy.

In terms of how long the ECP remains effective after taking it, once you have taken the pill, it works to prevent ovulation or fertilization for that cycle. However, if ovulation has already occurred, the ECP will not be effective. Therefore, it is crucial to take the pill as soon as possible after unprotected intercourse.

Additionally, if you have unprotected sex after taking the ECP, you are still at risk of becoming pregnant, as the pill does not provide ongoing protection. For ongoing contraception, it is advisable to consult with a healthcare provider about regular contraceptive methods.

In summary, the effectiveness of the emergency contraceptive pill varies depending on the type taken and the timing of ingestion. Levonorgestrel is most effective within 72 hours, while ulipristal acetate can be effective up to 120 hours. If you have further questions or concerns about emergency contraception or your reproductive health, it is always best to consult with a healthcare professional for personalized advice and guidance.