Had NT scan- question about gestational date

[tamina800]

Hi all
I had my NT scan today.
Everything looked wonderful.

However, this is what confused me - as per the gestational age given by my OB on my last week, I should have been 11w 6d today. The NT scan dated me at 12w 3d.

But the person doing the NT scan kept saying the doctor's dating is more accurate.

I am confused. Isn't the NT scan more extensive and thorough? I thought one of the things they do in NT scan is date your pregnancy.

Anyone had a similar experience? Now I don't know how far along I really am, although I want to believe 12w3d.

Thanks!

 

[mammag]

How did your doctor calculate gestational age?

 

[tamina800]

She calculated the gestational age based on the baby's measurements..

 

[mammag]

So, through another ultra sound of her own?

 

[tamina800]

Yes. I had an ultrasound 2 weeks ago, at 9w6d (based on her measurements)
Today in the NT scan, I was dated at 12w 3d (and constantly told it may not be accurate)

 

[mammag]

Ok, I was making sure your doctor didn't go just off of LMP, or uterine measurements (my uterus was measuring 11 weeks at 7 weeks, lol) They were probably both pretty accurate, they are pretty precise to up to 2 days off either way, so I would probably go with in the middle, so 10w1d then and 12w1d now makes pretty good sense.

 

[StranjeGirl]

If I remember correctly the baby grows very exact earlier on starting at like 7 weeks. I *think* the most accurate dating time is like from 7-10 weeks or around there...or maybe 8-10. I can't remember, but I do remember reading that you should go with an earlier reading unless it is really early, like 6 weeks, because as you get farther along they start to grow at different rates. Maybe that is why?

 

[SteffieLee]

The earlier ultrasounds are the most accurate. Xx

 

[babylove x]

Its normal to be within a week either direction xx

 

[My_First]

^^^^ exactly this. I was told that even the scan measured within a week either way they would leave my EDD the same. This is UK.

 

[Kezzybear]

Hi love, I'm a sonographer. The ultrasound at any time is correct to plus or minus 5-7 days.
The most accurate time to date a pregnancy via ultrasound is between 8-11 weeks. After this time, baby can flex and extend it's back/neck making them longer or shorter.
So, in conclusion, the dates from your early scan which made you 11w6d at the time of your Nt scan is most correct and that's why the person doing the NT scan didn't change your dates. If you measured a week or more bigger, they probably would have.

Hope his helps xx

 

[Rican47]

If I remember correctly the baby grows very exact earlier on starting at like 7 weeks. I *think* the most accurate dating time is like from 7-10 weeks or around there...or maybe 8-10. I can't remember, but I do remember reading that you should go with an earlier reading unless it is really early, like 6 weeks, because as you get farther along they start to grow at different rates. Maybe that is why?

Yep! This sounds absolutely correct. Yesterday, when I had my very 1st prenatal appointment, after they took my bloods and did my pap they were able to book me an appointment for the same morning because they said 7 wks is ideally the best time to do the dating scan. When the baby gets "older" they can just do their own thing, have their own rapid growths and such. Hope this helps

 

[tamina800]

Thanks everyone for clearing this up for me! I wasn't aware that 7-10/11 weeks dating is most accurate. I guess I'm back to 11w6d

 

[vickyandchick]

I was always told to go by the date they give you at your 12 week scan