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Ultrasound at 36 weeks

post #1 of 10
Thread Starter 
So how much would you put in stock on the 'due date' results of a 36 week ultrasound? I've heard the earlier ones are more accurate...my 21 week put 3/23 as the due date. My ultrasound for this week indicates I'm at 37 weeks rather than the 36 weeks...with the head circumferance showing 38. Do you think I could be farther than led to believe? (this weeks measurement put me at 37).... I know baby will come when God and baby wants baby to come, but I just feel like maybe I'm farther than they think and I've sort of felt this for awhile...that on top of all the pinching, pelvic bone pain and contractions here and there...not what I'm used to with the previous pregnancies that were years ago........just wondered what you all would think??
post #2 of 10
DDCC from April.

I'd put exactly 0 stock in an ultrasound this late for dating purposes. The most accurate dating comes from an ultrasound in the first 12 weeks. Babies grow at such wildly different rates in the third trimester that it's next to impossible to determine via ultrasound and size when baby will arrive.

It'll be soon, no matter what!
post #3 of 10
Quote:
Originally Posted by organicmom3 View Post
So how much would you put in stock on the 'due date' results of a 36 week ultrasound? I've heard the earlier ones are more accurate...my 21 week put 3/23 as the due date. My ultrasound for this week indicates I'm at 37 weeks rather than the 36 weeks...with the head circumferance showing 38. Do you think I could be farther than led to believe? (this weeks measurement put me at 37).... I know baby will come when God and baby wants baby to come, but I just feel like maybe I'm farther than they think and I've sort of felt this for awhile...that on top of all the pinching, pelvic bone pain and contractions here and there...not what I'm used to with the previous pregnancies that were years ago........just wondered what you all would think??
None. Actually, very little in the 21 week ultrasound as well -- only first trimester ultrasounds are decent at dating pregnancies. All the ultrasound now can KIND of tell is that he seems to be bigger than average. And size estimates can be wildly inaccurate at this point too!
post #4 of 10
I can't find original sources, but several articles mention that ultrasound dating in the third triimester can be off by as much as three weeks http://miscarriage.about.com/od/imme...ltrduedate.htm

Another article, slightly better. http://www.medscape.com/viewarticle/703501_3 I did the math and at 36 weeks, being 8% off means +/- 20 days.
post #5 of 10
Thread Starter 
I guess I knew this would be the response....it's just that I've always questioned the due date. The midwife had orignially went with 4/6 as she went with the first day of the last menstruation date and i KNEW that was wrong as to that made the conception date a total impossibility (no physical relations for at least a 10+ day period of time around it!), so I knew the 21 week ultrasound was more accurate then going by that date and it made more sense but I also wondered if the dd was before that too... My last TWO menstration periods were VERY light....so it just lingers in my mind that I'm not real sure about the due date at all....I guess so close to the end I just want it to be sooner....I'm ready to meet this little one!
post #6 of 10
I can't blame you for wanting the due date to be moved up and closer!! It's so hard to wait at the end!!

But, I echo the sentiments of the previous posters... The range of 'normal' at the end is so huge, that I put no stock into late ultrasound results. Some women birth full-term babies at just over 6 pounds and that's perfectly normal, while some birth 9+ pound babies that are just as normal! That's a LOT of difference in size, but all still normal
post #7 of 10
I think few providers would work very hard to stop a spontaneous labor after 36 weeks, so the only "benefit" you would get by officially moving the due date up is LESS leeway if you go over.

Even if my due date was a week earlier then the estimate, I would want to keep the later date as the official one to prevent fights about postdates induction.

But if the EDD from LMP didn't match conception, I would feel validated by those US estimates, too. I would just keep it to myself.

The exception would be if my midwife wasn't legally able to attend before 37.
post #8 of 10
Thread Starter 
Oh I'm not looking to change the due date "Officially"....just wondering for my own mind.....
post #9 of 10
Quote:
Originally Posted by organicmom3 View Post
I guess I knew this would be the response....it's just that I've always questioned the due date. The midwife had orignially went with 4/6 as she went with the first day of the last menstruation date and i KNEW that was wrong as to that made the conception date a total impossibility (no physical relations for at least a 10+ day period of time around it!), so I knew the 21 week ultrasound was more accurate then going by that date and it made more sense but I also wondered if the dd was before that too... My last TWO menstration periods were VERY light....so it just lingers in my mind that I'm not real sure about the due date at all....I guess so close to the end I just want it to be sooner....I'm ready to meet this little one!
Do you normally have 28 day cycles? Adjusting the LMP date to fit your cycle length might be more accurate.

Either way, pregnancies aren't really 40 weeks... more like 38-42, with the average first time mom going at 41 w 1 day, and 2nd and later going at 40w 5 days. And the average American mom going at 39 weeks because of inductions.
post #10 of 10
I know when I ovulated, so I know exactly how far along I am. My first two u/s showed the dd to the day of what it should be. My current u/s's at 34, 35, and 36 weeks are showing my due date 1 1/2 weeks ahead of what it is. So, no it is not accurate at this stage of the game.
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