How accurate are weight predictions via ultrasound?

[OceanPrincess]

Way inaccurate in my case - had a scan at 32wks and was told she was already over 3kg, to expect a big bubba as they can put on 250g a week in the last few weeks

DD was born at close to 40wks and she was only 3.7kg.

Putting on less than 700g in 8wks is highly unlikely... considering all they do in the last few weeks is gain weight, so it was very inaccurate.

[Traveller]

I had a scan 3 days before labout with DS2, predicted weight 7lb, actual weight 8lb 2oz. My sister decided against a VBAC because of a predicted weight of over 10lb (and I know that's not really a reason not to VBAC but she has it in her head she cannot birth a big baby as she is so slim) and her daughter was born weighing 8lb 2oz a couple of days later.

I's so interesting to see other people's experiences of inaccurate weight estimates.

[KimB]

My 4th I was told she was going to be over 10lb but she was only 8lb 4oz. I was freaking out because of the size she was supposed to be that I opted for an induction early but shouldn't have worried. I had a natural birth with gas. My others they never said what they were going to be lol

[sas85]

At 34 weeks they told me DD2 was 2.5kg so spot on the 50th % - well 6 weeks later DD2 was born at 2.96kg (more like the 10th %) so either it was way out, or she gained under 500g in 6 weeks which is I suppose possible as I don't feel my tummy got much bigger.

[carr2walks]

I had a scan with my son at 36w 4days and he was approx 3.6kg. We had him by c-section (planned) at 38w 4d because every time my Ob scanned me she could tell he was growing VERY fast, plus my BP was up. He came out 4.154kg andI was told there was no way I could of had him naturally as his head was already stuck in my pelvis.
Good luck!! Big babies are great!! He was in 000 by the time he was 3 weeks old...hehe...fatty bumba!

[appletree]

I had a growth scan at 36 weeks for DS where they said he was already 4kgs, he was born 4 weeks later at 4.62kgs, so i am guessing it was fairly accurate.

At the time i chose to believe it was inaccurate + or - 10%, and tried to convince myself that he was no more than 3.6kgs. The hospital still managed to unnecessarily try to scare the cr@p out of me with this info and then to try to talk me out of a VBAC.

[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.

[didispunk]

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