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How Acurate are ultrasounds?

I am 36 weeks and had a ultrasound and it showed me at 38 weeks.And also the baby was around 7 lbs.So How acurate are they?And I have been contracting.& dilating.So is it safe if I go in to labor at 37 weeks?

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Asked by chelsey09 at 9:48 PM on May. 13, 2009 in Pregnancy

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Answers (6)
  • I had my first child at 34 weeks. She had to stay in the NICU for a week, which was awful, but she was fine. 9 years later she is in the top readers of her grade and been on honor roll every semester since she started school!! 37 weeks and you child should be fine.


    Answer by Anonymous at 9:51 PM on May. 13, 2009

  • The further along you are in your pregnancy, the harder it is to be accurate. Late trimester ultrasounds can be off by up to 2 pounds and 2 weeks in either direction. I wouldn't put any stock in to what they said she weighs or measures.

    Answer by NoNonsenseMama at 9:56 PM on May. 13, 2009

  • the second poster is right, the further along the harder to tell b/c at that point they grow at such different speeds that they can only compare to mainstream. as far as if you deliver now, it is considered full term at 38 weeks, so you are alot closer to full term than you think you are (38-42 weeks is full term).

    Answer by vabchmommy at 10:05 PM on May. 13, 2009

  • I had an us at 36 weeks and it measured my DS at 39 weeks and 5 days and weighing 8lbs 11oz. we delievered a week later and he weighed in at 8lbs 14.5oz so it can be right on or off the us tech did tell us it can be off 20oz in either direction.

    Answer by newmommy61207 at 10:12 PM on May. 13, 2009

  • I had several ultrasounds with my son due to a spot on his liver they were watching. They kept telling me he was going to be 11 pds and talked me into a c-section. He was only 8 pds. They said they had never been so off on a weight before especially having as many ultrasounds as I did. I don't think they are totally accurate but for most people it is probally close.

    Answer by melody525 at 10:36 PM on May. 13, 2009

  • At this point the ultrasound dating is not very accurate. Early on they are. My ultrasound with my second showed me 2 weeks ahead of where my OVULATION date and original unltrasound put me and she came 5 days before the original due date. The weight on an ultrasound can be plus or minus 20% since they are only measuring bones and developing weight based on what an average baby with that length bone weighs so I wouldn't put much stock in those. Both my kids were estimated to be 9 lb babies and the first was 7 lbs 1 oz and the second was 7 lbs 11 oz at birth!

    Answer by aeneva at 7:36 AM on May. 14, 2009

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