Pregnancy Chances After Unprotected Intercourse and Emergency Contraception

Probability of Pregnancy

Hello, Doctor.
My menstrual period started on July 13 and ended on July 19.
According to the app, the safe period was from July 20 to July 22.
I had intercourse with my boyfriend on July 20 using a condom, and I took the emergency contraceptive pill 3-4 hours after.
On July 24, I experienced some light bleeding.

1.
With these precautions, is the chance of pregnancy less than 0.1%?
2.
Does the bleeding indicate that I will not become pregnant, or could it be a false menstrual period? Is there still a chance of pregnancy? Thank you, Doctor.

Y, 10~19 year old female. Ask Date: 2019/07/24

Dr. Huang Jianzhong reply Obstetrics and Gynecology

On July 13, the first day of menstruation began, and it ended on July 19.
According to the app, the safe period is from July 20 to July 22.
I had intercourse with my boyfriend on July 20 using a condom, and took emergency contraception 3-4 hours after.
On July 24, I experienced some bleeding (a small amount).

1.
With these precautions, is the chance of pregnancy less than 0.1%? Answer: Yes.

2.
Does the bleeding indicate that pregnancy is not possible, or is it a false menstruation, or is there still a chance of pregnancy? Answer: The bleeding is a side effect of the emergency contraception.

Reply Date: 2019/07/24

More Info

When it comes to understanding the chances of pregnancy after unprotected intercourse and the use of emergency contraception, it's essential to consider several factors, including the timing of intercourse in relation to the menstrual cycle, the effectiveness of the contraceptive method used, and the nature of any subsequent bleeding.

1. Pregnancy Chances After Unprotected Intercourse: Based on your timeline, you had unprotected intercourse on July 20, which falls within the fertile window of your menstrual cycle. The fertile window typically includes the days leading up to and including ovulation, which usually occurs around 14 days before the start of your next period. If your cycle is regular, and you ovulate around the midpoint of your cycle, there is a possibility of pregnancy if sperm is present during this time. However, since you used a condom during intercourse, this significantly reduces the risk of pregnancy. Condoms are about 85% effective with typical use, meaning that while there is still a small chance of failure, it is considerably lower than unprotected intercourse.

2. Use of Emergency Contraception: You mentioned that you took emergency contraception (EC) 3-4 hours after intercourse. Emergency contraception is most effective when taken as soon as possible after unprotected intercourse, ideally within 72 hours, but it can be effective up to 5 days after. The effectiveness of EC can vary, but it is generally estimated to reduce the risk of pregnancy by 75-89% when taken within the recommended timeframe. Given that you took it shortly after intercourse, your chances of becoming pregnant are significantly reduced. While it is difficult to quantify an exact percentage, it is reasonable to say that your chances of pregnancy could be less than 0.1%, especially considering the condom was used.

3. Understanding the Bleeding: The bleeding you experienced on July 24 could be attributed to several factors. It may be a side effect of the emergency contraception, as hormonal fluctuations caused by EC can lead to breakthrough bleeding or spotting. This bleeding is not indicative of pregnancy and is often referred to as withdrawal bleeding. It is important to note that this bleeding does not confirm that you are not pregnant; however, it is a common response to the hormonal changes induced by the emergency contraceptive pill.
4. False Menstrual Bleeding: The term "false menstruation" or "pseudo-menstruation" is not commonly used in medical literature. However, it is essential to understand that any bleeding that occurs after taking emergency contraception does not necessarily mean that you are not pregnant. If you were to experience a missed period or any other pregnancy symptoms in the following weeks, it would be advisable to take a pregnancy test for confirmation.

In summary, given your use of a condom and the timely administration of emergency contraception, your chances of pregnancy are very low. The bleeding you experienced is likely a side effect of the emergency contraception rather than an indication of pregnancy. If you have any concerns or if your period is significantly delayed, it is always best to consult with a healthcare provider for further evaluation and guidance.

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