Effectiveness of Emergency Contraceptive Pills After Unprotected Intercourse

The likelihood of pregnancy after unprotected intercourse during the ovulation period, followed by the use of emergency contraception, depends on several factors, including the timing of the emergency contraceptive pill (ECP) intake. If taken within 72 hours after unprotected sex, ECPs can reduce the risk of pregnancy by up to 89%. However, their effectiveness decreases the longer

The last three menstrual periods were from November 4 to November 10, December 14 to December 20, and January 10 to January 16.
The estimated next period is from January 9 to January 14.
On January 23 at 1:00 AM, unprotected sexual intercourse occurred, with the male partner not ejaculating but pre-ejaculate fluid potentially containing sperm, which can survive for more than three days.
An app indicates that the ovulation period is expected on January 25.
If emergency contraception is purchased and taken on January 23 at 10:00 AM, what is the likelihood of successful contraception, and when should symptoms be monitored to determine if contraception was effective?

Lan Tang, 20~29 year old female. Ask Date: 2024/01/23

Dr. Cao Guotao reply Obstetrics and Gynecology

Hello, I have responded to your inquiry.
Wishing you good health.

Reply Date: 2024/01/23

More Info

Emergency contraceptive pills (ECPs) are a crucial option for preventing pregnancy after unprotected intercourse. In your case, you had unprotected sex on January 23rd, and you are considering taking an ECP shortly after. The effectiveness of ECPs, such as levonorgestrel or ulipristal acetate, largely depends on how soon they are taken after unprotected intercourse.

Levonorgestrel, commonly known as Plan B, is most effective when taken within 72 hours (3 days) after unprotected sex, with its efficacy decreasing the longer you wait. It is estimated to be about 89% effective when taken within this time frame. On the other hand, ulipristal acetate (Ella) can be taken up to 120 hours (5 days) after unprotected intercourse and maintains its effectiveness throughout this period, making it a better option if you are closer to the 72-hour mark.

Given that you plan to take the ECP on January 23rd, which is the same day as the unprotected intercourse, you are within the optimal window for taking levonorgestrel. This means you have a high chance of preventing pregnancy, especially since you mentioned that the male partner did not ejaculate, although pre-ejaculate fluid can contain sperm.

Regarding your menstrual cycle, you noted that your last menstrual period started on January 10th, and you expect your next period around January 9-14. The timing of your cycle is relevant because if you are close to ovulation, the chances of pregnancy increase. However, since you are taking the ECP soon after unprotected intercourse, it should effectively inhibit ovulation or prevent fertilization.

After taking the ECP, it is important to monitor your body for any signs of pregnancy or changes in your menstrual cycle. You should expect your next period to arrive around the expected date, but it may be earlier or later than usual due to the hormonal changes induced by the ECP. If your period is more than a week late, it is advisable to take a pregnancy test to confirm whether or not you are pregnant.

In summary, taking the emergency contraceptive pill on January 23rd after unprotected intercourse is a proactive step towards preventing pregnancy. The sooner you take it, the more effective it will be. Keep track of your menstrual cycle and any symptoms you may experience in the following weeks, and consult a healthcare provider if you have any concerns or if your period is significantly delayed.

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