Conception Timing: A Guide for Expecting Mothers

Time of conception

Hello, I would like to ask you.
My period started around January 25, and I took a pregnancy test on February 20 which was negative.
On February 29, I went to the doctor for a pregnancy test, and the line was very faint.
The doctor said I had just conceived.
Yesterday, an embryo measuring 1 cm was seen on the ultrasound.
Can we estimate when conception occurred? Could it be from the intercourse on February 3? The current estimated due date is November 2.

Youyou, 20~29 year old female. Ask Date: 2016/08/17

Dr. Cao Guotao reply Obstetrics and Gynecology

Hello, a typical pregnancy test should be taken at least 12 days after conception to yield accurate results.
It is unlikely that the pregnancy is from the intercourse on the 2nd or 3rd.
Wishing you good health.

Reply Date: 2016/08/17

More Info

Understanding conception timing is crucial for expecting mothers, as it helps in tracking the development of the fetus and preparing for the arrival of the baby. Based on the information you provided, let’s break down the timeline and understand how conception is calculated.

You mentioned that your last menstrual period (LMP) started around January 25. The average menstrual cycle lasts about 28 days, but it can vary from woman to woman. Ovulation typically occurs about 14 days after the first day of your last period. Therefore, if we assume a regular cycle, ovulation would likely have occurred around February 8. This is usually the time when a woman is most fertile, and conception can happen if intercourse occurs within a few days before or on the day of ovulation.

You took a pregnancy test on February 20, which came back negative. This could be due to testing too early, as it may take a few days after conception for the hormone hCG (human chorionic gonadotropin) to reach detectable levels in urine. When you visited the doctor on February 29, the test showed a faint line, indicating that you were indeed pregnant, but it was still early in the pregnancy.

Given that the ultrasound showed a 1 cm embryo, this aligns with a gestational age of approximately 6 weeks, which would place conception around early February. Specifically, if you had intercourse on February 3, it is plausible that this could have led to conception, especially if it coincided with your ovulation period.

Your estimated due date of November 2 is calculated based on the standard method of adding 280 days (or 40 weeks) to the first day of your last menstrual period. This is a common practice in obstetrics to estimate the delivery date, assuming a regular 28-day cycle.

In summary, based on your timeline:
- Last Menstrual Period: January 25
- Estimated Ovulation: February 8
- Possible Conception Date: February 3 (if intercourse occurred around this time)
- Positive Pregnancy Test: February 29 (indicating early pregnancy)
- Estimated Due Date: November 2
It's important to remember that these calculations are estimates and can vary based on individual cycles and other factors. Regular prenatal check-ups will help monitor the health of both you and your baby, and your healthcare provider can provide more personalized insights based on your specific situation.

If you have further questions about your pregnancy or any concerns, don’t hesitate to reach out to your healthcare provider. They can offer guidance tailored to your needs and ensure that you have a healthy pregnancy journey.

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