Pregnancy Chances After Unprotected Intercourse: Your Questions Answered - Obstetrics and Gynecology

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When it comes to understanding the chances of pregnancy after unprotected intercourse, several factors need to be considered, including the timing of ovulation, the menstrual cycle, and the effectiveness of contraceptive methods used. In your case, let's break down the details to provide a clearer picture.

Your girlfriend's last menstrual period (LMP) was from February 22 to March 6. Typically, ovulation occurs about 14 days after the start of the last menstrual period, which would place her ovulation around March 7 to March 12. Since you mentioned that you had intercourse on March 11, 12, and 13, this timing is very close to her ovulation window, which increases the likelihood of pregnancy if no contraception was used.

However, you also mentioned that you used condoms during intercourse. Condoms are a reliable form of contraception when used correctly, with a typical effectiveness rate of about 85% to 98% in preventing pregnancy. If the condoms were used properly and did not break or slip off, the chances of pregnancy would be significantly reduced.

Your girlfriend received the Moderna vaccine on March 31. Vaccination does not affect fertility or the chances of becoming pregnant. It is safe to receive vaccines during the reproductive years, and there is no evidence to suggest that the vaccine would interfere with the menstrual cycle or pregnancy.

You noted that your girlfriend's period was expected at the end of March or early April, but as of April 14, she had not yet menstruated. A missed period can be concerning, especially if it is accompanied by other symptoms of pregnancy. However, stress, hormonal imbalances, changes in weight, and other factors can also lead to a delayed period.

You mentioned that you purchased a pregnancy test on April 10, which showed one line (negative), and an ultrasound on April 11 did not reveal any signs of pregnancy. A negative pregnancy test is generally a reliable indicator that pregnancy has not occurred, especially if taken after a missed period. Additionally, an ultrasound performed early in the pregnancy (around the time of your girlfriend's expected period) would typically show a gestational sac if pregnancy were present.

In summary, based on the information provided, the chances of pregnancy seem low due to the use of condoms and the negative pregnancy test results. However, if your girlfriend's period does not arrive soon, it may be advisable for her to consult a healthcare provider for further evaluation. Factors such as stress, hormonal changes, or other medical conditions could be contributing to the missed period.
If you have any further questions or concerns about reproductive health or pregnancy, it is always best to consult with a healthcare professional who can provide personalized advice based on a thorough assessment of the situation.