Pregnancy Chances After Unprotected Sex and Emergency Contraception

Probability of Pregnancy

Hello Doctor, on the morning of March 19, I had sexual intercourse with my boyfriend.
At first, we did not use a condom, but there was no ejaculation inside.
After that, we used a condom.
I took the emergency contraceptive pill "Plan B" within an hour after the incident.
I'm not sure when my next period will come.
What is the chance of pregnancy in this situation, and what are the possible side effects? Thank you, Doctor.

Niming, 10~19 year old female. Ask Date: 2016/03/20

Dr. Cao Guotao reply Obstetrics and Gynecology

Hello, emergency contraceptive pills can sometimes cause irregular menstruation.
It is best to use preventive measures beforehand.
If your period is more than a week late, consider consulting a gynecologist.
Wishing you good health.

Reply Date: 2016/03/20

More Info

When it comes to understanding the chances of pregnancy after unprotected sex and the use of emergency contraception, several factors need to be considered. In your case, you had unprotected intercourse on March 19, followed by the use of emergency contraception (Plan B) within an hour. This is a crucial step, as emergency contraceptive pills (ECPs) are designed to prevent pregnancy after unprotected sex.

Understanding the Mechanism of Emergency Contraception
Emergency contraception works primarily by delaying ovulation. If taken before ovulation occurs, it can prevent the egg from being released from the ovary. If ovulation has already occurred, ECPs may not be effective. The effectiveness of ECPs decreases the longer you wait to take them after unprotected intercourse, but they are most effective when taken as soon as possible.

Timing of Your Menstrual Cycle
Given that your menstrual cycle can vary, it's important to track when your next period is expected. If your cycle is typically around 28-31 days, ovulation usually occurs about 14 days before your next period. If you had unprotected sex close to your ovulation window, there is a higher chance of pregnancy. However, since you took the emergency contraceptive pill shortly after the incident, this significantly reduces your risk of becoming pregnant.

Symptoms and Side Effects
After taking emergency contraception, some women may experience side effects such as nausea, fatigue, headache, dizziness, breast tenderness, or changes in their menstrual cycle. It's not uncommon for your next period to be earlier, later, or heavier than usual after taking ECPs. If your period is delayed by more than a week, it is advisable to take a pregnancy test to confirm whether or not you are pregnant.

Pregnancy Testing
If you are concerned about the possibility of pregnancy, you should wait until at least a week after your expected period to take a home pregnancy test for the most accurate result. If the test is positive, or if you have any unusual symptoms, it is important to consult with a healthcare provider for further evaluation and guidance.

Conclusion
In summary, while there is always a risk of pregnancy with unprotected sex, taking emergency contraception significantly reduces that risk, especially when taken promptly. Monitor your menstrual cycle closely, and if you experience any unusual symptoms or a missed period, consider taking a pregnancy test. If you have any concerns about side effects or your menstrual cycle after taking the emergency contraceptive, do not hesitate to reach out to a healthcare professional for personalized advice.

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