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How accurate are growth scans?

(24 Posts)
jinglebellmel Tue 25-Apr-17 20:56:53

Growth scan today at 31 weeks as there were some concerns baby might end up a little small due to thyroid issues. She measured around 90th centile! Fundal height put her off the chart over 99th when it was only 40th centile 3 weeks ago. I'm a bit worried now that I'm having a whopper!

Does anyone have any experience of how reliable growth scans are at this stage? Maybe growth will slow down a bit or am kidding myself? Consultant didn't seem bothered by it, but it wasn't what I'd been expecting at all.

kshaw Tue 25-Apr-17 21:06:58

My growth scans were consistent at 28 and 31 weeks - I then had one at 35+2 and said her weight had evened out and said she was 5lb 4. I had her at 35+6 and she was 6lb 11! 28 and 31 weeks were saying she was gunna be a 10lb baby - I think it depends on the technician that does the measurements!

SpwJd Tue 25-Apr-17 21:48:17

I had growth scans late on in my first pregnancy.
After telling me I was having a big baby ( I'm tiny) they realised in fact I was having a small baby. ( he was lying transverse so apparently hat confused them.!) Had growth scans that predicted dc1 was to be 6lb 8 at delivery. He was 5 1/2 lb. with second pregnancy I was scanned regularly to check size as thought I may have another small one. Told he was quite small. At this stage I took them with a punch of salt. Dc2 was 7lb.
My 3 Pregnancy I need extra growth scans but again will take it all with a pinch of salt as it's only a prediction. They've not been right for me so far.

harleysmammy Tue 25-Apr-17 21:57:40

I'm being induced next Wednesday, a day after my due date, because I have an "enormous baby" but I had two scans yesterday and one said he was measuring 9lb and the other one (3 hours later) said 10 lb 6 oz..I know I'm having a big baby but I highly doubt my little one gained a pound and half in 3 hours. I think they're good at finding out whether it's a small or big baby but it's exactly how big or small is harder to get right x

vichill Tue 25-Apr-17 22:02:39

I had a scan quite lateish for a relatively small bump measurement. I was told she was on track to be 10lb +. She was 40+3 and just under 8lbs.

TwoDogs9 Wed 26-Apr-17 05:35:19

I had monthly growth scans, all of which showed a gargantuan baby and put the fear of God into me! However my bump always measured small. All measurements were taken from baby's femur length though as his head circumference was never measured due to his position. He arrived 38+2 weighing 7lb9oz but was quite long hence why the scans had him down as a hefty baby!! My sister had the opposite and was told repeatedly that she was going to have a very small baby (so bought loads of tiny baby clothes in preparation) and he weighed 9lb!

jinglebellmel Wed 26-Apr-17 08:22:29

Thanks everyone, seems it's a bit hit and miss then! Baby does have super long legs as has done since 20 weeks so maybe just going to be tall. My first was fairly petite so had been hoping for the same again.

VilootShesCute Wed 26-Apr-17 08:27:08

My second measured big at later scans. He was 10lb 2oz. Walked at seven and a half months and at 10y is a tall and healthy lean lad who is stronger than me!

haveacupoftea Wed 26-Apr-17 08:29:30

There is a margin of error of about 1lb I believe, also the scans aren't that accurate on their own, you need a few growth scans to build a trend - my baby for example is consistently on the 90th centile, he may not come out the exact weight they're predicting but he will be big for sure. The consultant won't worry unless the next growth scan shows the baby isn't following the pattern for their own growth, so if baby is off the chart big or doesn't grow as expected, which means they aren't thriving in the womb.

ofudginghell Wed 26-Apr-17 08:37:05

Told me on dc 2 growth scan she would weigh 4lb at birth but was 6lb 1/2 oz.

Dd 3 growth scan said 4.5lb and she was born at 6lb 1oz.

TeddyIsaHe Wed 26-Apr-17 08:37:28

My growth scan at 37 weeks estmated dd to be 10lbs at full term! shock She came out a diddy 6lb 11oz so I don't hold much trust in them, thank goodness! She was very long though, so perhaps why they estimated bigger.

funkybum Wed 26-Apr-17 08:38:07

I was scanned in early labour. They said 9lb. I laughed as firstborn was only 6.14. New baby was 9.1!

ItsNiceItsDifferentItsUnusual Wed 26-Apr-17 08:42:38

Haven't been right for me. Had one at 38 weeks for dc1 and was estimated under 7lb at birth, he was actually 8.5lb ...and my bump was tiny. I'm measuring big this time but scan showed baby at around 5oz at 35 weeks. Not sure what to think really!

WhisperingLoudly Wed 26-Apr-17 08:43:33

I was scanned by a fetal Med consultant during labour due to a placenta issue. DD was born 17 hours later weighing 1. 4 lbs less than scan had indicated. So IME not accurate at all.

arbrighton Wed 26-Apr-17 08:47:48

They use femur (thigh bone) length, abdomen and head measurements to estimate the weight so as my bean has legs that are rather shorter (but tracking a centile), the weights are coming out on 50 centile while head and abdomen are up near 90th!
I've got two more scheduled yet, thanks to the possibility of having been exposed to Zika

jinglebellmel Wed 26-Apr-17 08:54:15

Okay I'm going to hope it's a little out then and try not to worry, has to come out now however big it is I guess! No more growth scans booked as they were only worried she maybe small and about blood flow - now they are happy that's not the case they aren't worried.

Abrighton, that must be a worry, hope everything is going well.

eurochick Wed 26-Apr-17 09:04:40

They seem to be very variable. A friend was told to expect a whopper but had a 7lber. Mine was done by the head of foetal medicine due to complications and was within 30g.

Mrsknackered Wed 26-Apr-17 09:55:05

Meh. I had growth scans in my whole first pregnancy and was told he's probably be around 5lb. He was 2 weeks late and 7lb 14oz.
DC2 was also 'small' and estimated at 6lb. He was 7lb 3oz born at 39 weeks. So a very average weight!

silkpyjamasallday Wed 26-Apr-17 09:59:30

My late scan was totally accurate as to DDs size, she was 7lbs 8oz when she was born and that was the weight she was predicted to be from the growth chart based on her size at the time of the scan.

However, a friend was induced as they said her baby was tiny and had stopped growing, and she was almost 9lbs when born so they can be wrong. This is at the same hospital too!

pardrej Wed 26-Apr-17 10:02:37

We had one that said 6.11 at 12 on Friday. He arrived on Saturday morning, 6.8!

pardrej Wed 26-Apr-17 10:02:59

But experience seems to vary wildly!

SairdyJane25 Wed 26-Apr-17 10:37:45

I had scan at 38 wks to be told he was 8lb 12 then, delivered at 40+4 and he was 8lb 6.5, take it with a pinch of salt xx

Sarasue1967 Wed 26-Apr-17 11:43:04

In my experience not very. They told me that I was going to have a whopper (something in the region of 9-10lbs) and I spent weeks worrying about the destruction of my kitty 😿. In the end dd1 turned up at 7,2........

RainbowChasing Wed 26-Apr-17 12:20:18

With my dd I was told that she would be big- I was given various measurements ranging between 8.8lb to 10lb. She was 7lb 5oz when she born.

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