HealthCareMagic is now Ask A Doctor - 24x7 | https://www.askadoctor24x7.com

How To Determine The Date Of Conception And Due Date Using Ultrasound Scan?

Posted on Fri, 24 Jul 2015

Question:
Hi doc

I had my ultrasound done on July 3, which say 8 week 1 day old. My first date of my last menstrual period is April 24, 2015.
I am at a 35 day cycle and always start ovulated on the 17th day. Also on May 13 - 16, I have blood spotting.

1) does the 8 week 1 day old per ultrasound meaning "gestational age" or " fetal age"?
The technician does not specify and only reply that there is a chart to compute the date of conception.

2) per my blood test did on XXXXXXX 9, I was told that I was at my 4 the week. So my doc was very confirmed that I must have conceived in the week of May 10-16.

3) with the above info, what would be by due date and conception date?

Many thanks

Answered by Dr. Deepti Verma (49 minutes later)

Brief Answer:
Calculation as below

Detailed Answer:
Hi XXXXXXX I have gone through your question and understand your concerns. I will like to answer your questions as you asked:
1.8weeks1day is the fetal age, which is calculated based on the crown rump length( CRL) of the fetus seen on ultrasound and is then calculated by the software in ultrasound machine.
2. By your blood test, the date of conception told by your doctor is correct. It is anywhere between 10-17 th May.
3. By the information you have provided, your expected delivery date is 11 th February, 2016.
Estimated date of conception is anywhere between10 -17 th May, 2015.
Hope you found the answer helpful. Please do get back for further queries.
Wishing you good health.
Regards,
Dr Deepti Verma

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

Follow up: Dr. Deepti Verma (20 minutes later)

Thank you doc!

Please review enclosed ultrasound report taken on July 3 and comment.

Is it possible that I have sex on 17th and be conceived on the same day?

Yes doc. U re amazing. I now recalled that my due date per the technician is feb 11 2016.

Answered by Dr. Deepti Verma (2 hours later)

Brief Answer:
Normal intrauterine pregnancy

Detailed Answer:
Hi XXXXXXX thanks for responding. The ultrasound report you have enclosed shows an intrauterine pregnancy with a good decidual reaction and a normal fetus. This means that the pregnancy is well implanted and growing well.
It is very well possible that the conception has occurred on 17 th May after you had intercourse on the same day.
Hope you found the answer helpful. Please do get back for further queries.
Wishing you good health.
Regards,
Dr Deepti Verma

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

Follow up: Dr. Deepti Verma (11 hours later)

Hi doc

Thank you for ur responses

would u please kindly explain the computation to the due date of feb 11 2016?

Answered by Dr. Deepti Verma (17 hours later)

Brief Answer:
calculation as below

Detailed Answer:
Hi dear, since your gestation age was 8 weeks1 day on 3 rd July, 2015, then your last menstrual period according to28 day cycle comes out to be 4 th May, 2015. Then according to Naegle's formula, we add 9 months and 7 days, and the expected date of delivery comes to be 11 thFebruary, 2016.
Hope you found the answer helpful. Please do get back for further queries.
Wishing you good health.
Regards,
Dr Deepti Verma

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

Follow up: Dr. Deepti Verma (6 hours later)

Hi doc

Just to recap the fact that my LMP is April 24 2015 and I am at 35 cycle

In ur earlier reply u indicated that my ultrasound dated July 3 2015 showing that I am 8w1d so it is a fetal age. But in ur most recent response u suggested that it is genstation age. I am a little confused. Would u please clarify?

Using the Naegla's formula, counting from LMP, my due date is XXXXXXX 31 2016 , not feb 11 2016

I was told that even the ultrasound showed feb 11, 2016. It should not change the conception date and the actual due date cause they re often off. Is that true?

Many thanks doc

Answered by Dr. Deepti Verma (10 hours later)

Brief Answer:
Tried to make calculation simple

Detailed Answer:
Hi dear, I know it is a bit confusing. I will try to explain you in more simpler terms. Calculation of expected due date is done by Naegle's formula, and it is applied assuming that the lady has a normal28 day cycle. We add 9 months and 7 days to last menstrual period to calculate the due date.
If somebody has irregular or prolonged menstrual cycles, then the due date is calculated by the first trimester ultrasound. Whatever the fetal age comes, we assume it to be gestation age and retrospective calculate the last menstrual period according to it, and then we apply Naegle' s formula to calculate the the due date.
However, it does not changes the original conception date.
Hoping that I was able to explain you a bit.
Please do get back for further queries.
Wishing you good health.
Regards,
Dr Deepti Verma

Note: For further follow up on related General & Family Physician Click here.

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