Pregnancy Timing: When Did It Happen? - Obstetrics and Gynecology

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Understanding the timing of pregnancy can be quite complex, especially when considering factors such as ovulation, fertilization, and the sensitivity of pregnancy tests. Based on the timeline you provided, let's break down the events to clarify when conception likely occurred.

Your girlfriend's last menstrual period (LMP) was around late February, and you mentioned that her cycle is approximately 28-30 days. This means that ovulation would typically occur around 14 days after the start of her last period, which would place it around mid-March. The timing of ovulation is crucial because it is during this window that she would be most fertile and capable of conceiving.

You had sexual intercourse on March 20, which is close to the estimated ovulation period. If ovulation occurred around March 14-16, sperm from the intercourse on March 20 could indeed fertilize an egg if it was still viable. Sperm can live inside the female reproductive tract for up to five days, so if ovulation occurred later than expected, there is a possibility that the sperm from March 20 could have led to conception.

Regarding the pregnancy tests, it is important to note that home pregnancy tests work by detecting the hormone human chorionic gonadotropin (hCG), which is produced shortly after a fertilized egg implants into the uterus. This implantation typically occurs about 6-10 days after fertilization. If fertilization occurred on March 20, implantation would likely happen around March 26-30. The first test you took on March 26 may have been too early to detect hCG, which is why it showed a negative result. By April 2, enough hCG would have been produced to yield a positive result on the pregnancy test.

To summarize, it is indeed possible that the sexual intercourse on March 20 resulted in pregnancy, and the positive test on April 2 reflects that conception. The negative test on March 26 can be attributed to the timing of implantation and the sensitivity of the test.
In conclusion, the timeline suggests that the events align with the possibility of conception occurring from the intercourse on March 20, particularly if ovulation occurred later than initially estimated. If you have further questions or concerns about the pregnancy, it is always a good idea to consult with a healthcare provider for personalized advice and guidance.