Calculating Conception Date: Your Pregnancy Timeline

I would like to know the date of conception?

Hello, I would like to ask you, I got my period around January 25, took a pregnancy test on February 20 which was negative, then went to the doctor for a pregnancy test on February 29 and the line was very faint.
The doctor said I had just conceived, and yesterday an embryo measuring 1 cm was seen on the ultrasound.
Can we estimate when conception occurred? Also, if I had intercourse on February 3 and the pregnancy test on February 20 was negative, is there still a possibility of being pregnant?

Yoyo, 20~29 year old female. Ask Date: 2016/03/09

Dr. Cao Guotao reply Obstetrics and Gynecology

Hello, it is difficult to determine the exact time, but it should be around February 15.
Wishing you good health.

Reply Date: 2016/03/09

More Info

To calculate your conception date and understand your pregnancy timeline, it's essential to consider several factors, including your menstrual cycle, ovulation timing, and the results of your pregnancy tests.

Based on the information you provided, your last menstrual period (LMP) began around January 25. If we assume you have a regular menstrual cycle, ovulation typically occurs about 14 days after the first day of your last period. Therefore, if your cycle is around 28 days, you would likely have ovulated around February 8. If you had sexual intercourse around February 3, it's possible that sperm could have survived in your reproductive tract until ovulation, which would make conception possible.

You mentioned that you took a pregnancy test on February 20, which returned a negative result, and then another test on February 29, which showed a faint line indicating a positive result. The faint line suggests that you were likely in the early stages of pregnancy at that time. This could mean that conception occurred shortly after your ovulation, possibly between February 8 and February 10, depending on the timing of ovulation and the implantation of the fertilized egg.

It's important to note that pregnancy tests measure the hormone human chorionic gonadotropin (hCG), which is produced shortly after a fertilized egg implants in the uterus. If you tested too early, the levels of hCG may not have been high enough to detect, which could explain the negative result on February 20.
Regarding your question about the possibility of pregnancy despite the negative test on February 20, it is indeed possible. If you conceived shortly after your ovulation, the hCG levels may not have been detectable at that time. Therefore, the timeline you provided suggests that conception likely occurred shortly after February 8, with the positive test on February 29 confirming the pregnancy.

In summary, based on your cycle and the timing of your tests, it is reasonable to estimate that your conception date was around February 8 to February 10. If you have further concerns or questions about your pregnancy, it is advisable to consult with a healthcare provider for personalized advice and care. They can provide you with more accurate information based on ultrasounds and other assessments as your pregnancy progresses.
Additionally, if you have any concerns about your pregnancy, especially considering your previous history of miscarriage, it is crucial to seek medical advice. Early prenatal care can help monitor the health of your pregnancy and address any potential issues.

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