Pregnancy Chances After Unprotected Sex: When to Test

Probability of Pregnancy

I would like to ask the doctor: I had sexual intercourse on September 20th with ejaculation inside the condom.
Because I was worried, I took emergency contraception on the night of September 21st.
My last period was on August 28th, and my menstruation should be arriving soon, but it hasn't come yet.
I'm very concerned about being pregnant.
Should I take a pregnancy test? If so, when would be the best time to test? Is there a possibility that I could be pregnant?

Ying, 20~29 year old female. Ask Date: 2020/09/27

Dr. Cao Guotao reply Obstetrics and Gynecology

Hello, the chances of pregnancy should be low.
You can take a pregnancy test 12 days after intercourse.
Wishing you good health.

Reply Date: 2020/09/27

More Info

When it comes to understanding the chances of pregnancy after unprotected sex and determining the appropriate time to take a pregnancy test, several factors need to be considered. Based on your situation, you had unprotected sex on September 20 and took emergency contraception (the "morning-after pill") the following evening. Your last menstrual period started on August 28, and you are now concerned about a potential pregnancy since your period has not yet arrived.

First, let's discuss the effectiveness of emergency contraception. The morning-after pill is most effective when taken as soon as possible after unprotected intercourse. It can reduce the risk of pregnancy by preventing ovulation, fertilization, or implantation of a fertilized egg. However, it is not 100% effective, and its efficacy decreases the longer you wait to take it after unprotected sex. If you took the pill within 24 hours, you maximized your chances of preventing pregnancy.

Now, regarding your menstrual cycle: If your cycle is typically around 28-31 days, your period would be expected around September 25 to September 29. Since you mentioned that your period has not arrived yet, it is understandable that you are feeling anxious. Stress, hormonal fluctuations, and the use of emergency contraception can all affect your menstrual cycle, potentially causing delays.

As for testing for pregnancy, the best time to take a home pregnancy test is typically about one week after your missed period. In your case, if you expected your period around September 25-29, you should consider taking a pregnancy test around October 2-6 for the most accurate results. Home pregnancy tests work by detecting the hormone hCG (human chorionic gonadotropin) in your urine, which is produced after a fertilized egg implants in the uterus. Testing too early may result in a false negative, as hCG levels may not be high enough to detect.

If your test is positive, it is advisable to schedule an appointment with a healthcare provider for further evaluation and confirmation. If the test is negative but your period still does not arrive, you may want to consult a healthcare professional to discuss your concerns and explore other potential reasons for the delay.

In summary, while there is a possibility of pregnancy given the circumstances, taking the emergency contraception pill significantly reduces that risk. Monitor your body for any signs of menstruation, and plan to take a pregnancy test about a week after your expected period for the most reliable results. If you have any further concerns or if your period does not arrive, seeking medical advice is always a good step to ensure your health and peace of mind.

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Hello, the probability should be low, but you can take a pregnancy test to check. Wishing you good health.

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