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How accurate is estimated birth weight?

(37 Posts)
Londongirl84 Mon 13-Jan-14 19:44:38

At a scan we had today (35 weeks) they estimated our baby to weigh 8-8.5lbs on her due date. How accurate is this??

Ratbagcatbag Mon 13-Jan-14 19:46:37

Not great. So don't panic!!! At 33 weeks, I was told baby was already 7-8lbs. It certainly made the sweepstake interesting. (12lb guesses shock ) dd was born 37+4 at a ok 6lb12oz. grin

Londongirl84 Mon 13-Jan-14 19:49:36

They estimated she already weighs 5lbs 9oz which seems big for 35 weeks!! Glad you say they were wrong for you ratbag x

Not great. Estimated 8lb on due date, arrived a little late at 10.4lb

WitchOfEndor Mon 13-Jan-14 19:53:28

Not. DS was supposed to be 10lbs and he was only 7lb 4oz (thank goodness)

Piggytastic Mon 13-Jan-14 20:09:11

Ds1 estimated 6lb and was 8.5, ds2 estimated 9lb+ and was 8.3
Not accurate at all!

AnitaBlake Mon 13-Jan-14 20:09:16

They estimated DD1 as 5lb at 34w, she was 4lb 11oz when born at 38w.

ISpyPlumPie Mon 13-Jan-14 20:09:40

DS1 was estimated as 6lb but was 9lb 2oz. O know this is an error in the opposite direction to reassuring but
a) it was based on prodding by a mw rather than a scan
b) he was almost two weeks late.

With DS2, I'd worked out he'd be a 10lber based in his scan weight at 30 weeks allowing for 1/2lb per week gain until birth. He was actually 7lb 10oz.

Everything I've heard suggests estimating birth weights is a rough science at best.

DD was estimated to be 8lbs at 38 weeks. She was 5lb 12oz at 40 weeks so ime not accurate at all!

DipDabDabDip Mon 13-Jan-14 20:11:47

I got told "well she's not going to be a small baby" at 32ish weeks. Dd came out 11 days overdue at a tiny 6lb 15oz.

I don't think they're very accurate at all.

Pommes Mon 13-Jan-14 20:13:39

Not accurate at all. Was made to feel quite worried I had a very big baby, delivered at 39 weeks a 8lb 4oz DS.

Londongirl84 Mon 13-Jan-14 20:20:29

This is reassuring! I don't want a big baby!

Pinkbell123 Mon 13-Jan-14 20:32:17

I'm 35 weeks and today was told mines already 7lbs 8 so I hope its a bit out! Rescan in 2 weeks time so will see what that one says.

3bunnies Mon 13-Jan-14 20:35:53

ds was estimated at 8lb, greedy guzzler got an extra 12oz out of me by the time he was born 30hrs later or maybe the scan was a tiny bit inaccurate

KateH32 Mon 13-Jan-14 21:57:53

Not accurate. Was told 8lbs - got 10lbs 3oz!

FrequentFlyerRandomDent Mon 13-Jan-14 22:03:55

It is not very accurate. It is a calculation based on diameter of thorax if I remember correctly. There is an average 400 gr error margin either side of the prediction.

FrumiousBandersnatch Mon 13-Jan-14 22:04:19

They underestimated in my case. Estimated birth weight of approx 7lb from 32 week scan, every hcp involved in birth examined me and told me baby was not big, DD born with assistance and weighed 9lb.

GlitzAndGiggles Mon 13-Jan-14 22:05:19

DD was estimated 6.9lbs and born 7.7lbs

sittingagain Mon 13-Jan-14 22:06:57

At 36 weeks plus 5, at 11am, ds2's weight was estimated to be 8lb.

He was born 14 hours later, weighing 7lb 4oz.grin

RandomMess Mon 13-Jan-14 22:14:13

They kept telling me I measured small for dates, and the baby wasn't big (even though I'm a short arse and looked huge) she weighed 10lb 6oz...

Inkspellme Mon 13-Jan-14 22:21:41

scan estimated 7lbs. dd arrived 10lb 8oz.

funnily, she was breech and the doc who was going to try to turn her said by feel she was closer to 10lb. That was the same day as the scan. He didn't turn her as she was too big to move. I'm five foot 1" in height.

i had various growth scans in last pregnancy and estmates themselves varied by about 2 pounds. seems even dodgier than the tape measure!

AnythingNotEverything Mon 13-Jan-14 22:28:52

There's no need to fear a big baby. Most newborns have heads of a very similar size, and it's the head and shoulders that are tricky to pass. They can be really long or fat, and it doesn't make any difference.

However, it is thought that big babies have more help from gravity.

Big babies get stuck just as often as small babies - positioning is much more important than size.

Also, big babies are much easier to handle. You're less scared of breaking them manipulating their arms into babygrows as they're stronger.

LottyLikesWindows Tue 14-Jan-14 00:55:26

I would take it with a pinch of salt. At 34 week scan we were told that DD would weigh 8lb. She was in fact 9lb3oz so not even close.

Last week I met a poor woman who was also told to expect an 8lb baby too but ended up delivering a huge 12lb9oz baby.

LottyLikesWindows Tue 14-Jan-14 00:58:23

Oh and I second anything's post - my little strong chunky monkey is very easy to dress. No faffing about worrying I'll break her tiny arms. She's very strong!

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