Effectiveness of Emergency Contraceptive Pills After Unprotected Sex

Are emergency contraceptive pills effective?

On Tuesday night, there was intimate contact, but no penetrative sexual intercourse, only external rubbing.
On Friday night, around midnight, I couldn't hold back anymore, and since we didn't have a condom, we engaged in sexual activity.
The process involved several pauses and starts.
At one point, I felt that I ejaculated, so I pulled out.
The next morning, I immediately bought emergency contraception for her to take.
However, she already had some irregularities in her menstrual cycle, and after our encounter on Friday, her period stopped.
Is there a risk of pregnancy?

Xiao Ming, 10~19 year old female. Ask Date: 2017/10/21

Dr. Cao Guotao reply Obstetrics and Gynecology

Hello, the chances of getting pregnant are low, but it is always best to take preventive measures beforehand.
Do not rely on the safe period.
If your period is overdue by more than a week, it is advisable to see a gynecologist.
Wishing you good health.

Reply Date: 2017/10/21

More Info

Emergency contraceptive pills (ECPs), commonly referred to as "morning-after pills," are designed to prevent pregnancy after unprotected sexual intercourse or contraceptive failure. The effectiveness of these pills, such as Ella (Ulipristal Acetate), is a crucial topic for anyone who has had unprotected sex, especially during the fertile window of the menstrual cycle.

In your situation, you engaged in non-penetrative sexual activity on Tuesday and then had unprotected intercourse on Friday. Given that sperm can survive in the female reproductive tract for up to five days, there is a possibility that sperm from the earlier encounter could still be viable when you had unprotected sex on Friday. This is particularly concerning if your partner was nearing ovulation, as this is when the chances of conception are highest.

You mentioned that your partner took the emergency contraceptive pill the morning after the unprotected intercourse. Ella is effective for up to 120 hours (5 days) after unprotected sex, with its efficacy being highest when taken as soon as possible. Studies indicate that Ella can reduce the risk of pregnancy by approximately 85% when taken within this time frame, although its effectiveness diminishes the longer you wait. Since your partner took the pill the following morning, she is within the optimal time frame for the medication to work.

Regarding your partner's menstrual irregularities, it is not uncommon for emergency contraceptive pills to cause changes in the menstrual cycle. Some women may experience spotting, delayed periods, or even an early onset of menstruation after taking ECPs. If your partner's period is late by more than a week after taking the pill, it would be advisable for her to take a pregnancy test to confirm whether or not she is pregnant.

In terms of the risk of pregnancy, while the emergency contraceptive pill significantly reduces the chances, it is not 100% effective. Factors such as the timing of ovulation, the timing of the pill intake, and individual variations in menstrual cycles can all influence the outcome. If your partner experiences any unusual symptoms or if her period is significantly delayed, seeking medical advice would be prudent.

In summary, while the emergency contraceptive pill is a reliable option for preventing pregnancy after unprotected sex, it is essential to understand that it is not infallible. The best course of action is to monitor for any signs of pregnancy and consult a healthcare provider if there are concerns. Additionally, for future sexual encounters, consider discussing more reliable and consistent contraceptive methods to prevent such situations from arising again.

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