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Can ULTRASOUND confirm CONCEPTION DATE accurately?

Resolved Question:

For an OBGYN:

LMP: 10/11, EDD: 7/20 (all first trimester ultrasounds at 6-13 weeks have given a range of 7/18-7/22)
Positive Preg Test: 11/10/2014
First Trimester Scan: CRL 62.6mm at 13 weeks GA
All Second Trimester Scans: 18/20 weeks, have given range of 7/20-7/22 (GA was in line with measurements)
Conception points to: 10/25 -10/29

1. Can you confirm the conception date range is accurate? Can conception have occurred in September and calcs be off?
2. One encounter on 9/5, period on 9/8 and then second period on 10/11, could either of these be considered implantation? 9/5 encounter was no penetration just ejaculation on outside.
3. Second encounter 10/25-10/27, can you confirm that this is the encounter that led to pregnancy? Can ultrasound be off by that much?

Prenatal care = Very high, appts every week in the early stages due to bleeding. First appt transvaginal ultrasound on 11/21, only sac seen, followed by heartbeat on 11/26.
Looking for: General Peace of mind that conception date range is accurate.

Category: OBGYN

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Category: Infertility Specialist
Dr. Aarti Vazirani is online now

Expert:  Dr. Aarti Vazirani replied 4 Days.

Thanks for writing to us with your health concern.
1. Yes the conception date is accurate. If conception had occurred in September, consistent scans would have shown the EDD to be in June , and not July. Calculations cannot be off by so much.
2. No, none of these can be considered implantation.
3. Ultrasounds can be off by maximum 5 - 7 days, not 4 weeks to a month.
Yes, you have my certified professional opinion that you conceived in October last, and not September.
Can you upload the copies of the ultrasound scans please , particularly the initial few scans in the first trimester ?
Those would also help in consolidating my opinion, which says, please do not be anxious, you cannot have conceived in September.
All the best
Please feel free to discuss further.

Patient replied :

Follow Ups:
1. So there is no concept of late implantation or late conception? How far do encounters need to be to establish this kind of question? Does interaction without penetration generally lead to preg?
I'm attaching my 1/12 first trimester scan for reference. Please advise.

Expert:  Dr. Aarti Vazirani replied 3 Days.

Interaction without penetration rarely leads to a pregnancy.
The encounters, if spaced out less than 10 days, can be confusing.
Here I have no doubt about the date of conception.
Else I would have asked you to go for a paternity test.
No, there is no doubt in my mind.
Please be assured.

Patient replied :

Did the ultrasound fall completely in line? Does it solidify conception date within a closer range?
Just curious about the question I asked earlier, is late conception something that occurs often? Is that a concern here?

Expert:  Dr. Aarti Vazirani replied 2 Days.

Late conception can occur, but then the scans would show that.
The dates of your last period, and the dates of the scans , all scans, fall perfectly in line.

Patient replied :

Hi Dr Aarti, Can you please advise on my following concerns: I've noticed that I can't find your credentials and I noticed that your picture is being used on a different site with a different last name. As you can understand I'm just a little nervous since I don't know about your exact qualifications. If you wouldn't mind can you please clarify this, or refer me to another specialist if possible? Also, I don't think you answered my last question very clearly: 1. Since all dates line up, does conception range become solidified? IE - if I am a small person, wouldn't my measurements be smaller (even if I am further along) and be prone to a larger error bar? If the baby comes early does the conception range change? Thanks!

Expert:  Dr. Aarti Vazirani replied 1 Day.

The confusion arose because my surname changed after marriage and it must not have been updated on the other site.
I am a practising gynecologist in India, and I have been handling queries across all major sites.
Now, about your query.
Okay, let me elaborate further.
Suppose you conceived on the 5th of September.
Now, in the first case, without ejaculation, pregnancy is rare.
Then you had a period ( or you fear implantation bleeding ) again on the 8th, just 3 days later , which is unheard of.
Implantation bleeding occurs a week after conception.
Then you again had another period in October, which would not have happened if you were pregnant !
That is the biggest proof or argument I have.
Next, assuming you are a small person, if you had conceived in September, first trimester scans would have still shown the conception as being from September, because in the initial stages, the size of the baby does not matter.
What matters for dating is the yolk sac, appearance of pregnancy sac, and the heartbeat in the baby.
ANd these parameters appear on a fixed universal schedule for all women, irrespective of size.
Whether a woman is small or big, these date schedules do not change.
For example, a petite woman would show a heartbeat around 6 weeks, and a robust one too.
All your scans consistently point towards a conception date in October, they all fall in line.
I have no doubt about this.
I hope this convinces you.
Let me know if it does not, I do not mind trying more !!
Have a good day .

Dr. Aarti Vazirani
Category: Infertility Specialist
Residency: Obstetrics & Gynecolog, BJMC,Civil hospital, Ahmedabad, 2008
Post Graduate: MS (Obstetrics & Gynecology), B.J. Medical College, Ahmedabad, 2008
Medical School: MBBS, B.J. Medical College, Ahmedabad, 2004
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