Determining Conception Date: A Guide for Expecting Mothers

Date of conception during pregnancy?

The first day of the last menstrual period was on May 7, with a cycle length of 26-28 days.
The menstruation lasted for five days.
On May 11, I thought I had finished my period, so I engaged in external ejaculation (I noticed a little bit of blood from May 11 to May 12).
On May 14, I had unprotected intercourse with ejaculation inside.
On May 21, I had unprotected intercourse with ejaculation inside again.
My period was late on June 9, and I tested positive for pregnancy with a faint line.
An ultrasound showed a thickened endometrium but no embryo.
On June 21, an embryo was detected at 5 weeks and 6 days, and on June 30, it measured 7 weeks.
I would like to know what date conception likely occurred.

Qu, 20~29 year old female. Ask Date: 2021/07/05

Dr. Cao Guotao reply Obstetrics and Gynecology

Hello, it seems more like May 21.
Wishing you good health.

Reply Date: 2021/07/05

More Info

Determining the conception date can be a complex process, especially for expecting mothers who are trying to understand their pregnancy timeline. Based on the information provided, we can analyze the details to estimate the likely date of conception.

First, let's break down the menstrual cycle and the events leading up to the pregnancy. You mentioned that your last menstrual period (LMP) started on May 7, and your cycle typically lasts between 26 to 28 days. This means that ovulation would likely occur around 12 to 14 days after the first day of your last period, which would place your ovulation window around May 19 to May 21.

You reported having unprotected intercourse on May 14 and again on May 21. Since sperm can live inside the female reproductive tract for up to five days, the intercourse on May 14 could potentially lead to conception if ovulation occurred shortly after. However, the intercourse on May 21 is also within the ovulation window, making it a viable candidate for conception as well.

The pregnancy test you took on June 9 showed a faint positive line, which indicates that implantation likely occurred around that time. Implantation typically happens about 6 to 10 days after conception. Given that you had a positive test on June 9, this aligns with the possibility that conception occurred shortly after your last intercourse on May 21.

When you had your ultrasound on June 21, it showed a gestational age of approximately 5 weeks and 6 days, which would correspond to a conception date around May 21. The subsequent ultrasound on June 30, which showed a gestational age of 7 weeks, further supports this timeline.

In summary, based on your menstrual cycle, the timing of intercourse, and the ultrasound findings, it is likely that conception occurred around May 21. However, it is important to note that estimating the exact date of conception can be challenging due to variations in ovulation timing and the lifespan of sperm.

For expecting mothers, understanding the conception date can help in planning prenatal care and preparing for the arrival of the baby. It is always advisable to consult with a healthcare provider for personalized guidance and to confirm the pregnancy timeline through ultrasounds and other assessments.

In addition to understanding conception dates, it is crucial for expecting mothers to maintain a healthy lifestyle, including proper nutrition, regular prenatal check-ups, and managing stress. These factors can significantly impact both maternal and fetal health throughout the pregnancy. If you have any concerns about your pregnancy or need further clarification on your timeline, do not hesitate to reach out to your healthcare provider for support and advice.

Similar Q&A

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To estimate the date of conception, we can consider the details provided. Your last menstrual period (LMP) started on February 10. Typically, ovulation occurs about 14 days after the start of the last menstrual period, which would be around February 24. You mentioned having sex...

Dr. Huang Yuande reply Obstetrics and Gynecology
The gestational age shown by ultrasound is usually more accurate, so you can count back six weeks from May 7, which may indicate the date of conception.

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Hello, the date of conception is usually estimated accurately through ultrasound at around 8 to 9 weeks of pregnancy. Based on your description, it is difficult to make an accurate calculation and explanation. Thank you! Wishing you peace and health, Dr. Zhang.

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