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How To Determine The Date Of Conception Using Ultrasound?

Posted on Mon, 27 Jul 2015

Question: On July 3 2015, my ultrasound says I am 8 week1 day. My First day for the last period is April 23, 2015. My due date is Feb 11, 2016. I was told that my conception date is May 7, 2015, but I thought it would be between May 10 - May 13. Would you please tell me my conception date? thanks

Answered by Dr. Dr. Rakhi Tayal (35 minutes later)

Brief Answer:
Near 20th May.

Detailed Answer:
Hello,
Thanks for trusting us with your health concern.
As per the ultrasound scan your date of conception should be near 20th May. There can be a discrepancy of 5-6 days in the date calculation. If your last period started on 23rd April then it is a late conception. The pregnancy test should have been positive after 30th May.
Please feel free to discuss further. I will be glad to answer the follow up queries that you have.
Wishing you good health.
Regards.
Dr. Rakhi Tayal.
For future query, you can directly approach me through my profile URL http://bit.ly/Dr-Rakhi-Tayal

Above answer was peer-reviewed by : Dr. Chakravarthy Mazumdar

Follow up: Dr. Dr. Rakhi Tayal (9 hours later)

Thank you doc. However, I always ovulated on the 17th day after my first day of the period (April 24) being may 10. And on May 13 - may 16, I have little blood came out during these days and the ovaluation kit showed that I just ovulated. Also, my first blood test on XXXXXXX 9 shows that I was pregnant with 4 weeks, being the week of May 10 - may 16. So If you suggested that My conception date is May 20 and could be backdated for 5-6 days, does it mean that I can be conceived on May 14?

Answered by Dr. Dr. Rakhi Tayal (3 hours later)

Brief Answer:
25th May is more likely.

Detailed Answer:
Hello.
Thanks for writing again.
A blood test on XXXXXXX 9 showed a 4 weeks pregnancy. It seems to be most accurate. This suggests that the conception happened 14 days prior to the test. The most likely date of conception is around 25th May. Ovulation kit may show a false positive result.
Hope my answer is helpful.
Do accept my answer in case there are no further queries.
Regards.

Above answer was peer-reviewed by : Dr. Chakravarthy Mazumdar

Follow up: Dr. Dr. Rakhi Tayal (1 hour later)

Hi doc

My family doc confirmed the XXXXXXX 9 blood test with me that I was 4 week pregnant and so I would be conceived in the week of May 10. Also when I went to see a doc on May 19, he confirmed that I have already passed my ovaluation. If I am to conceived on May 25 but the last time I have sex was May 17. Would it be possible? I am very confused... Thank you doc

Answered by Dr. Dr. Rakhi Tayal (7 hours later)

Brief Answer:
You conceived on May 17.

Detailed Answer:
A pregnancy of 4 weeks means you conceived 2 weeks earlier. The pregnancy duration is calculated from the date of last periods and not from the date of conception.
If you had last sex on May 17 then most likely you conceived on May 17. There can be a margin of error of 6-7 days while calculating dates based on blood test as the hormonal values can vary from individual to individual.
Regards.

Above answer was peer-reviewed by : Dr. Raju A.T