How Effective Are Emergency Contraceptive Pills After Unprotected Sex?

How is the effectiveness of emergency contraception determined?

I got my period on October 8th and had unprotected intercourse with my boyfriend on November 1st, without being able to withdraw in time.
I took the emergency contraceptive pill on November 2nd, but as of today, November 10th, I still haven't had any bleeding or my period.
Is this normal? Is the medication still effective? Am I at risk of being pregnant?

Baozi, 20~29 year old female. Ask Date: 2015/11/10

Dr. Lü Lizheng reply Obstetrics and Gynecology

Please observe if there is any bleeding similar to menstruation.
If there is, it is likely that you are not pregnant.
However, if there is no bleeding, it does not necessarily mean you are pregnant.
You can wait a few days and take a home pregnancy test to confirm whether you are pregnant.
Sincerely, Dr.
Li-Cheng Lu, Taoyuan Hospital.

Reply Date: 2015/11/10

More Info

Emergency contraceptive pills (ECPs), such as Ella (Ulipristal Acetate), are designed to prevent pregnancy after unprotected sexual intercourse or contraceptive failure. Their effectiveness largely depends on the timing of administration relative to ovulation and the menstrual cycle.

In your case, you had unprotected intercourse on November 1st and took the emergency contraceptive pill on November 2nd. Ella is effective for up to 120 hours (5 days) after unprotected sex, with the highest efficacy when taken as soon as possible. Studies indicate that Ella can reduce the risk of pregnancy by approximately 85% when taken within this timeframe. However, its effectiveness may decrease as time passes, especially if you are close to your ovulation period.

Regarding your concern about not having your period by November 10th, it is essential to understand that ECPs can cause changes in your menstrual cycle. Some women may experience a delay in their next period after taking ECPs, while others may have earlier or lighter periods. This variability is due to the hormonal changes induced by the medication. Therefore, not having your period by the expected date does not necessarily indicate pregnancy.

However, if you are concerned about the possibility of being pregnant, it is advisable to take a home pregnancy test. Most home pregnancy tests are reliable and can detect pregnancy about a week after a missed period. If the test is positive, or if you continue to experience symptoms of pregnancy (such as nausea, breast tenderness, or fatigue), you should consult a healthcare provider for further evaluation.

In summary, the emergency contraceptive pill you took is still effective, and the absence of your period could be a side effect of the medication. It is crucial to monitor your body and consider taking a pregnancy test if your period does not arrive soon. If you have any further concerns or experience unusual symptoms, do not hesitate to reach out to a healthcare professional for personalized advice and support.

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