Pregnancy Chances After Unprotected Sex: Key Insights - Obstetrics and Gynecology

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When it comes to understanding the chances of pregnancy after unprotected sex, several factors need to be considered, including the timing of intercourse in relation to the menstrual cycle, the presence of ovulation, and the results of pregnancy tests.

In your case, you mentioned that your girlfriend's menstrual cycle typically ranges from 28 to 32 days. You had unprotected sex on February 14, which was the last day of her menstrual period. Generally, ovulation occurs about 14 days before the start of the next menstrual period. Therefore, if her cycle is regular, ovulation would likely occur around the middle of her cycle, which would be approximately 14 days after the end of her period. This means that ovulation would likely occur around February 28 to March 2, depending on the length of her cycle.

Since you had unprotected sex on the last day of her period, it is less likely that sperm would survive long enough to fertilize an egg, as sperm can live up to five days in the female reproductive tract. However, if she had a shorter cycle, there is still a possibility that sperm could be present during her ovulation window.

Regarding the pregnancy tests, the results you described indicate that the pen-style test showed only one line (C), which typically means negative for pregnancy. The faint line on the tray-style test (T) could indicate a very early pregnancy or could be a result of an evaporation line, which can occur if the test is read after the recommended time frame. It's essential to follow the instructions carefully for accurate results.

Given that her period is now two days late, it would be advisable to wait a few more days and then retest. If the second test is still inconclusive or if she continues to miss her period, it would be wise for her to consult a healthcare provider for further evaluation. A blood test can provide a more definitive answer regarding pregnancy.

In summary, while the chances of pregnancy from the encounter on February 14 are relatively low, they are not zero, especially considering the variability in menstrual cycles. The best course of action is to wait a few more days and retest, and if there are still uncertainties, seeking medical advice would be the next step. Additionally, if you and your girlfriend are considering becoming sexually active without protection in the future, discussing reliable contraceptive methods would be beneficial to avoid unintended pregnancies and to manage sexual health effectively.