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June 2015 Moms
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Are measurement scans ever accurate?

jessicarae0316jessicarae0316 member
in June 2015 Moms
My due date was moved at the beginning of my pregnancy, based on my ultrasound. I went from a due date of June 9 to June 20. That's a huge jump in my opinion.

My first daughter was 9 lb 8 oz. they did an ultrasound two days before I delivered and they said she was measuring 7 lbs. Her due date was based solely the first ultrasound, and according to that date she was 2 weeks early.

My husband had a similar, but opposite experience with his daughter from his first marriage. They were told she was going to be over 9 lbs, and she was just over 7 when she was born shortly after.

I am now measuring a week and a half ahead (almost aligned with my original due date....hmm?). My dr wants to do a measuring ultrasound in two weeks, and as much as I love seeing my little cutie, I just don't know if ultrasounds are an accurate way to determine size. Has anyone had a scan be accurate in detecting size? Anyone else's due date been moved and now worried that it shouldn't have been?
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Re: Are measurement scans ever accurate?

  • sschwegesschwege member
    Just like anything they are accurate sometimes, but according to the ACOG they can be 'imprecise' I've heard the margin of error is +1/-1 pound. 

    Here's a little more about what the ACOG writes:
    https://www.aafp.org/afp/2001/0701/p169.html

    For what it's worth measurements by a tape measure can vary by as much as 2 weeks in either direction and still be considered within the normal range.  With DD I consistently measured 2w behind she was born at 40w3d weighing 7lb15oz, with DS I consistently measured 1 week behind and DS was also born at 40w3d weighing 8lb12oz.  It's all just a guessing game at this point. 

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  • mrs1374amrs1374a member
    They are sometimes. I had one 2 days before my first daughter was born, and she was 7lbs 10oz and the day she was born she was 7 lbs 13 oz. however, with this baby I'm kind of hoping it's off because she measured 5 lbs 12 oz at 32 weeks and 6 lbs 8 oz at 34 weeks. I haven't had another one since.
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  • HayesRN13HayesRN13 member
    No
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  • klkonwiklkonwi member
    edited May 2015
    Why not use this twice in one day.
    For the record I know they aren't accurate yet still want to know the weight.... Because I'm crazy. :)
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  • jessicarae0316jessicarae0316 member
    Why do physician insist on using them when they can be so wrong? Like I said I am happy to get a chance to see my little guy, but it seems strange. I'm sure what is going to happen is they are going to want to induce because of his size. My experience with it was 14 years ago, so I thought maybe they were more accurate these days.
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  • knwilliams01knwilliams01 member
    I think it also depends on who is doing the ultrasound. Being hospitalized for the 6.5 weeks before delivery, I got growth scans every 2 weeks. The Monday before I delivered on Wednesday my growth scan said 5lb5oz. LO was born on Wednesday at 5lb3oz at 36 weeks exactly - so pretty darn accurate for us. The ultrasound tech doing our scan only worked with high risk doctors and had a great track record with her growth scan accuracy.
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  • jessicarae0316jessicarae0316 member
    sschwege said:

    Just like anything they are accurate sometimes, but according to the ACOG they can be 'imprecise' I've heard the margin of error is +1/-1 pound. 

    Here's a little more about what the ACOG writes:
    https://www.aafp.org/afp/2001/0701/p169.html

    For what it's worth measurements by a tape measure can vary by as much as 2 weeks in either direction and still be considered within the normal range.  With DD I consistently measured 2w behind she was born at 40w3d weighing 7lb15oz, with DS I consistently measured 1 week behind and DS was also born at 40w3d weighing 8lb12oz.  It's all just a guessing game at this point. 


    She did say that me measuring 1.5 weeks ahead was normal, but want to do a growth scan because of my history of having a big baby.
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  • jessicarae0316jessicarae0316 member
    knwilliams01 said:

    I think it also depends on who is doing the ultrasound. Being hospitalized for the 6.5 weeks before delivery, I got growth scans every 2 weeks. The Monday before I delivered on Wednesday my growth scan said 5lb5oz. LO was born on Wednesday at 5lb3oz at 36 weeks exactly - so pretty darn accurate for us. The ultrasound tech doing our scan only worked with high risk doctors and had a great track record with her growth scan accuracy.

    Sounds like you had a great U/S tech! Hopefully sometime the technology will be there so that there isn't so much room for error. Hope you and LO are doing well!
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  • Cateash77Cateash77 member
    How do you feel? Do you feel (or can you remember feeling) as big now as you were in your first pregnancy? This may be a better indication. EDD is supposed to be quite accurate from early ultrasounds I have heard, but size not so much....my first boy was measuring "just slightly above average" my OBS thought he would be in the 7-8 pound range and he was 9 pound. If even docs with 30 yrs experience can't tell then I guess maybe there is no easy way...There is, however a very detailed calculation that some researchers from John Hopkins I think came up with around 4 years ago that is supposed to be able to predict within 8% accuracy either way, you could google that. I tried to work it out, but my maths is awful and am therefore hoping I won't have a 12 pound baby which is what my calculation came out as!
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