Pregnancy Chances After Unprotected Intercourse: A Comprehensive Guide

Probability of Pregnancy

The last menstrual period started on February 21.
I had unprotected intercourse on March 2, but the withdrawal method was used (withdrawn just before ejaculation).
I took emergency contraception within two hours.
On March 20, I took a home pregnancy test, which was negative.
On March 21, I visited a gynecologist, who performed a urine test that also showed no pregnancy, and an ultrasound did not reveal anything significant.
I was prescribed medication to induce menstruation.
On March 23, I took another urine test, which also showed one line.
What is the likelihood of pregnancy?

Mira, 10~19 year old female. Ask Date: 2023/03/23

Dr. Zhang Kunmin reply Obstetrics and Gynecology

Hello, based on your description, if you have had a regular menstrual period, it is likely that you are not pregnant.
If your period is late or if you are uncertain, it is advisable to consult a physician for evaluation.
Thank you! Wishing you peace and health, Dr.
Chang.

Reply Date: 2023/03/23

More Info

Understanding the chances of pregnancy after unprotected intercourse can be a source of anxiety for many individuals. In your case, you had unprotected intercourse on March 2nd, and you took emergency contraception (the "morning-after pill") within two hours. You subsequently tested for pregnancy on March 20th and March 21st, both of which returned negative results. Additionally, an ultrasound performed by your gynecologist did not reveal any signs of pregnancy.
To assess your situation, let’s break down the factors involved:
1. Timing of Intercourse: The timing of your menstrual cycle plays a crucial role in determining the likelihood of pregnancy. Ovulation typically occurs about 14 days before the start of your next period. If your last menstrual period started on February 21st, you would likely ovulate around March 7th. Since you had intercourse on March 2nd, it was close to your ovulation window, which can increase the chances of conception.

2. Emergency Contraception: The emergency contraceptive pill (ECP) is designed to prevent pregnancy after unprotected intercourse. It is most effective when taken as soon as possible after the event, ideally within 72 hours. Since you took it within two hours, the likelihood of preventing pregnancy is significantly increased. ECPs work primarily by delaying ovulation, which means if ovulation has already occurred, the effectiveness may be reduced.

3. Pregnancy Testing: Home pregnancy tests and urine tests conducted by healthcare providers measure the hormone hCG (human chorionic gonadotropin), which is produced during pregnancy. Testing too early can yield false negatives, but since you tested on March 20th and 21st, it is unlikely that you are pregnant, especially given the negative results and the ultrasound findings.

4. Ultrasound Findings: An ultrasound can provide a visual confirmation of pregnancy. If no gestational sac or other signs of pregnancy were observed, this further supports the conclusion that you are not pregnant.

5. Overall Probability: Given the timing of your intercourse, the prompt use of emergency contraception, and the negative pregnancy tests along with the ultrasound results, the probability of pregnancy appears to be very low.
In conclusion, while there is always a small risk of pregnancy with unprotected intercourse, your proactive measures significantly reduce that risk. If you continue to have concerns or experience any unusual symptoms, it is advisable to follow up with your healthcare provider for further evaluation and peace of mind.
For further reading and resources, consider looking into reputable health websites such as the American College of Obstetricians and Gynecologists (ACOG) or the Centers for Disease Control and Prevention (CDC), which provide comprehensive information on reproductive health, contraception, and pregnancy.

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