Emergency Contraception: Assessing Pregnancy Risks After Unprotected Sex - Obstetrics and Gynecology

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When it comes to understanding the risks of pregnancy after unprotected sex and the use of emergency contraception (EC), it's essential to consider several factors, including the timing of intercourse in relation to the menstrual cycle, the effectiveness of the emergency contraceptive pill (ECP), and any subsequent symptoms or bleeding.

In your case, your girlfriend's last menstrual period (LMP) was from November 8 to November 14, and she had unprotected sex on November 13 and again on November 15. Since her cycle appears to be regular, we can estimate that ovulation likely occurred around November 22, assuming a typical 28-day cycle. The days leading up to ovulation are considered the "fertile window," and having unprotected sex during this time increases the risk of pregnancy.

After the unprotected intercourse, your girlfriend took an emergency contraceptive pill within one hour, which is a positive step. ECPs, such as Plan B or Ella, are most effective when taken as soon as possible after unprotected sex. They work primarily by delaying ovulation, preventing fertilization, or inhibiting implantation of a fertilized egg. The effectiveness of ECPs can be as high as 89% if taken within 72 hours, but their efficacy decreases the longer you wait.

The bleeding that your girlfriend experienced on November 19 and 20 could be a side effect of the emergency contraceptive pill. It is not uncommon for ECPs to cause changes in menstrual bleeding patterns, including spotting or breakthrough bleeding, which can resemble a menstrual period. This bleeding is generally not a sign of pregnancy and is often a result of hormonal changes induced by the medication.

Regarding the likelihood of pregnancy, since your girlfriend took the ECP promptly after unprotected intercourse, the chances of becoming pregnant are significantly reduced. However, no contraceptive method is 100% effective, and there is still a small risk of pregnancy, especially if ovulation had already occurred prior to taking the ECP.

If her next period is delayed beyond a week from the expected date, it would be advisable for her to take a home pregnancy test to confirm whether or not she is pregnant. Home pregnancy tests are generally reliable and can provide results as early as the first day of a missed period.

In summary, while the risk of pregnancy exists after unprotected sex, the timely use of emergency contraception significantly reduces that risk. The bleeding experienced after taking the ECP is likely a side effect rather than an indication of pregnancy. Monitoring her menstrual cycle and taking a pregnancy test if her period is late will provide further clarity. If there are any concerns or unusual symptoms, consulting a healthcare provider is always a good idea for personalized advice and support.