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Accuracy of ultrasound at guessing weight of baby?

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I've heard so many people say the doctors guessed the baby's weight by ultrasound and were off by 2 lbs or so. They think my baby weighs 10lb 4oz now. I'm 4 days past my ...show more
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Hi! You got some good comments. I was in your shoes a few years ago. I was told the baby was 10#2 at 37 weeks. She was born with no problem at 39.5 weeks and weighed 10#3, which would have put her about 9-ish lbs at the time of the u/s. Big babies run in the family and I later had an 11#5 baby, again with no problem. In the absence of gestational diabetes, babies over 10 lbs. are rare.

The hospital (midwives, docs) went nuts trying to push me into a c-section based on the u/s estimate. I declined because they gave me no evidence-- only anecdotes of their personal experience that they had seen shoulder dystocia and "it's really bad."

It can be really bad. However, the problem with their claim was that 1) there is no truly accurate predictor of fetal weight and 2) shoulder dystocia occurs unpredictably and 50% of the time it occurs in babies that are not considered macrosomic (big). So if they couldn't tell with scientific accuracy the actual weight of the baby, then as far as anyone knew, I wasn't actually at an increased risk of shoulder dystocia.

Most cases of SD are resolved with no injury. It would take 3,700 of scheduled cesareans on suspected macrosomic babies to prevent ONE case of permanent brachial plexus injury.

Sorry... long answer. Anyway, sorry you're having to focus on morbid stuff at this point in your pregnancy. Another thing to keep in mind is that there is a recent study suggests that inducing a macrosomic baby with Pitocin makes shoulder dystocia 23 times more likely.

I had to fight to give birth normally, unfortunately. I'm not sure if they're giving you the c/s push or not, but ask what you can sign in advance to let them know you understand their concerns if you are fine with labor taking its course. Good luck! –Jill

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Great info, this is why I was worried about inducing and ending up with a c-section. Fortunately I ended up going into labor the night I asked this question and he was born after a 4 hour total labor at 10lbs 8.7oz. He had no problems at all. Thanks!
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  • MO~Mommy answered 6 years ago
    when I was almost 38 weeks they did an ultrasound and my son was estimated to be 9 lbs 2 oz and they scheduled a c section because my doctor was worried about shoulder dystocia and my son ended up being 10 lbs 3 oz born 3 days after my ultrasound.
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  • ~*Mama-of-Two*~ answered 6 years ago
    I dont think you need to worry about a 10 pound baby unless it runs in your family. My husband was 10 pounds when he was born and our son was 9 pounds. Doctors never know for sure how big the baby is, the ultrasound is just an estimate.
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  • Proud Mama of 1! ☮ answered 6 years ago
    Yeah.. they don't really know.

    My sister in law was in your shoes.. they told her that her son was over 10lbs and they wanted to do a C-Section b/c he was too big to fit through the birth canal... well she had the C-Section but was PISSED OFF when she found out her son only weighed 6lbs 11oz! He just had a big head!

    They take weight estimates based on body part measurments and that is HIGHLY inaccurate.
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  • dina3sisters answered 6 years ago
    i just came back from the dr's office and the dr took a guess at the baby's current weight. She says the baby should gain 1/2 a lb per week from now on. i'll let you know in a couple weeks if she was accurate! good luck sweetie :)
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  • Riecey answered 6 years ago
    everyone i know who has had estimated they were off by 1/2 lb up to 4lbs, dont know how that is possible...the baby was 9times out of 10 smaller
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  • Landon & Danica's Momma answered 6 years ago
    horrible.. they are never right
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  • Accuracy of ultrasound at guessing weight of baby?
    I've heard so many people say the doctors guessed the baby's weight by ultrasound and were off by 2 lbs or so. They think my baby weighs 10lb 4oz now. I'm 4 days past my due date and baby has measured at least a week ahead from my first ultrasound. They said it could be off by a pound. How many of you were told your baby would be this big and it was much smaller? And were any told baby was this big and it was bigger?! Women who have delivered 10+ lb babies, did your baby have shoulder dystocia?
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