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How accurate is ultrasound with size of baby?

I'm 37 weeks today and just got back from my ultrasound apt. The ultrasound measured at 34.5 weeks , baby being aprox. 5.5 pounds...I am due nov. 28th...just wanted to know if this sounds right, and just how accurate this method was with some of your babies. It's just that im used to having 8 pounders (boys) this one is a girl for sure.


Asked by guitarmom101 at 10:49 AM on Nov. 6, 2009 in Pregnancy

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Answers (16)
  • I've heard they can be really off. I had an ultrasound to check the size of my son around 37 weeks too, they said he would be about 7 1/2 lbs on his due date and short. They didn't give me a length estimate but his femur measured several weeks behind compared to the rest of him, he was born the next week; so 2 weeks early, at 7 1/2 lbs and 21 inches. My kids all seem to have short femur lenghts in ultrasounds, but they have long torsos which make up for it, and I don't think that is measured.

    Answer by mybella81 at 10:59 AM on Nov. 6, 2009

  • She was 1 pound smaller than the US says and I don't think that the due date was accurate based upon the US. They induced me at 38 weeks and she stayed in the NICU for another 1.5 weeks before she came home as her lungs weren't quite up to par.

    Answer by Jademom07 at 10:51 AM on Nov. 6, 2009

  • none of mine were ever really accurate.

    the one I can really remember is #2 they said at my 37week u/s that baby was an 11pounder. she was born at 39weeks weighing 7lb11oz. no where near the size they said she was.

    Answer by hypermamaz at 10:52 AM on Nov. 6, 2009

  • @ 39 weeks (was really wanting to know the sex! so the made an exception) i was told that dd was no bigger than 6 lbs- and that was on the big side of their estimate. at 41 1/2 weeks, i birthed an almost 8 1/2 lb baby! no, they aren't accurate.

    they were over 1 1/2 lbs off with both of my ds's

    Answer by ObbyDobbie at 10:58 AM on Nov. 6, 2009

  • good....this is easing my mind a little

    Answer by guitarmom101 at 11:02 AM on Nov. 6, 2009

  • Mine was way off for my daughter. All along they kept telling me she was a "little baby" with a lot of fluid. Even right before my c-section they told me that. She ended up being 9 pounds. I wouldn't go by what they say - good luck!

    Answer by mompam at 11:09 AM on Nov. 6, 2009

  • The farther into pregnancy, the less accurate. Yours could be off by a couple of pounds.
    I have never had any ultrasounds with my pregnancies, but read about them all the time.
    For better accuracy, have an experienced pair of hands palpate to estimate.

    Answer by doulala at 11:14 AM on Nov. 6, 2009

  • Well sorry to burst your bubble but 4 babys for me and they were all correct,like right on! Also they told my friend her baby was around 9lbs and they were correct. Just listen to your doctor. I didn't agree with a US with my boy and he was in the NICU because it was too soon.I was barely 38 weeks and he was 36 just like the uS said! Some pics on my page! Your baby will be here soon enough. BTW US done @6-8 weeks are very accurate and doctor goes off that.Either that or baby is small for that gestation. We can share our exp,but I would listen to your doctor.

    Answer by Steff107 at 11:17 AM on Nov. 6, 2009

  • Sorry I wasn't incinuating you were in a hurry! I'm just saying when it's all done and said baby will be here soon enough and it won't even matter!lol Good luck hunn!

    Answer by Steff107 at 11:20 AM on Nov. 6, 2009

  • I had an u/s 4 days before my induction with my son and it said that he was 6 lbs 5 oz. He was born 5 days later weighing 5 lbs 7 oz so it was about a pound off with him.

    I had an u/s 2 weeks before my induction with my DD and it said she was 7 lbs 4 oz but she was born 2 weeks later weighing 6 lbs 7 oz so it was about 2 pounds off at the point it was done

    Answer by Jaydin_Makenna at 12:11 PM on Nov. 6, 2009