How accurate are weight predictions via ultrasound?

[Alan]

This is an extract from their own policy yet they still try to give a birth weight


Australasian Society for Ultrasound in Medicine
Policies and Statements
D7

Statement On Normal Ultrasonic Fetal Measurements

June 1991, Reaffirmed May 1996, Revised May 2001

FETAL WEIGHT
No formula for estimating fetal weight has achieved an accuracy which enables us to recommend its
use.

[~Kaz~]

Why am I not surprised Alan??

Y'know, I didn't have a dating scan beyond 18-20 weeks and my doc didn't try to estimate DS's size. I was grateful cause I didn't really need the stress of having a number and having no idea how accurate it was. They should all stop doing this (throwing numbers around willy nilly) imho.

[Tegam]

I had a scan at 34weeks with DD2 and was told she was 4kgs i had her two weeks later and she was 3.2kgs. They are normally 10% wrong either way and they can be up to 20% wrong! Just plan for your baby huni. Dont worry about the size. Your body new how to grow it why wouldnt it know how to birth it!

Happy birthing and i cant wait to read your birth story!

[mummy of 3 boys]

i had a scan at 32wks and it was estimating DS to be 4lb 12oz between then and 37wks 5 days when i had him he jumped to 7lb 15oz

i wouldn't worry

when i was in labour though a midwife checked my tummy and estimated a 3.5kg baby she was spot on he was 3.6kg's!!!

[didispunk]

My sonographer the other day said can be out 400g either way.

[Traveller]

My sonographer the other day said can be out 400g either way.

I think your sonographer was underexagerating a bit, I have knows scans to be more than 2lbs out (that's almost a kg)

[teresa]

My sonographer the other day said can be out 400g either way.

my scan the day before DS was born was definately a kg out!!

[Tegam]

my scan the day before DS was born was definately a kg out!!

The day before! wow, did you feel like going back and saying something?

[teresa]

no i was just glad that he was safe and i didnt have to worry anymore! it just shows that they are very rarely accurate tho.

[Faithful Mumma]

Well, I had a scan the day before DS was born predicting his weight to be just on 9lb.......he was 11lb 2oz!!!!

[kungfubecca]

they arn't. too many variables like how much fluid the mum retains.

My GP had a poke around with my last bubs, by feel at 38 weeks and said I rekon this is about a 7lb. She had an extra week to pork up and came out at 7lb 9oz. He was pretty spot on.