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how reliable is the estimated weight by scan measure?

(22 Posts)
superwormissuperstrong Mon 25-Apr-16 21:15:40

So have just had my 34 week scan for my second baby and been told that they want me to have weekly scans because the estimated weight has changed from just above the 10 centile line to just below it (nowhere near the 5 centile line)
I'm only having to attend the scans because I had just turned 40 when I found out I was pregnant - all other things (bmi, blood pressure, glucose, blood tests, etc) are normal and the consultants, sonographers and midwifes keep asking me why am I having these scans and weirdly its me that has to tell them that they arranged them automatically and I assume its because of my age.
I don't mind the extra scans - more chances to see the baby, but it seems to me to be overly cautious. Even the consultant said that the chances are its because it was a different sonographer and I remember reading on here that the estimated weight is a really unreliable reading.
Oh and the other measures which I think are actuals - head circumference, abdomen circumference and femur length are tracking along the same centile, umbilical artery and liquor volume are virtually the same readings.
Am I right to try and play down the seriousness of being just above 10 centile to just below? (Especially to family who are probably going to freak out and go on and on about it - can't avoid them knowing about the scans because I will need them for the childcare for DS)
Any one got experience of being called back for more growth scans and how did you stop it from causing yourself more stress and anxiety, when I want to be quietly just preparing for birth?

danadas Mon 25-Apr-16 22:41:47

I did in my third pregnancy for baby being too big. Had scans weekly from 30 weeks and was told I was carrying a 'massive' baby. They offered induction at 38 weeks which I refused. I ended up delivering in my own time at almost 43 weeks a 7lb 11ozs baby. I believe growth scans are notoriously unreliable and I am glad I went with my gut instinct.

In terms of reducing stress/anxiety, I went to the scans and listened to what they had to say but given that everything seemed fine apart from the perceived size I was firm in my decision to wait and luckily they respected that without too much trouble.

KnitsBakesAndReads Tue 26-Apr-16 03:38:24

I agree, growth scans seem to be notoriously inaccurate. I had an extra scan at 39 weeks as my bump was measuring big. They were predicting my baby would be nearly 10 lbs but he was born 3 days later almost a pound lighter than they'd predicted.

MyFriendsCallMeOh Tue 26-Apr-16 03:44:09

Very inaccurate. I had weekly scans (overseas) and was told that dd2 was measuring big at a 41 week scan, she was just under 8lbs.

YokoUhOh Tue 26-Apr-16 04:05:19

Very inaccurate. DS was hung to be a 10lb baby; he was 6lb7oz!

LucyMouse Tue 26-Apr-16 04:18:16

At 37wks I was told baby was already measuring 7lb4oz. Four weeks later I gave birth to a 7lb3oz baby.

DontDeadOpenInside Tue 26-Apr-16 04:35:33

Yes, totally wrong ime too. I have a large family so have had many, many ultrasounds etc. I have been told almost every time that the baby would be of a small/ average size at these growth scans. Each of my children, bar two, have been on time or a little past my due date. They all weighed between 9lb 7oz and 11lb 6oz, the majority being over 10 and a half pounds. The two that were early one was 9lb 9oz at 36 weeks you can imagine my shock the other was also born at 36 weeks but was a tiny for me 7lb 14oz . If I had anymore, which I'm not, I would not take a blind bit of notice.

winchester1 Tue 26-Apr-16 05:06:15

Mine were both spot on predicted birth weights were within 100gs of predicted weights. With both I had an extra growth scan around 34weeks and with dc1 I had an additional scan around 38weeks as he was looking small but with a big head in comparison.
I guess it depends on the experience of the person measuring and both times mine were done by people learning and checked by their superviser/ teacher.
(also I'm not in the UK so maybe being I a small quite hospital helps them take their time.

PixieMiss Tue 26-Apr-16 05:14:25

Another one here who was told to expect 10lbs+. That was at a 36 week growth scan.

In reality he was 7lb13 at 40+11.

princesspineapple Tue 26-Apr-16 06:40:54

My 38 week growth scan said to prepare for a 9 and a half pound baby... Returned all the first size clothes for size 0-1 months and when DD was born at 41 weeks she was 8lbs3oz and had no clothes that actually fit!

MrsGlam Tue 26-Apr-16 07:34:46

I was told to expect a big baby with a big head at 37+5 he was predicted at 8lb 2oz.induced at 38+3 and he was 7lb 6oz with a normal size head. So they aren't that reliable in my opinion.

shouldwestayorshouldwego Tue 26-Apr-16 07:38:55

DS gained 12lb in 24hr from emergency scan to birth weight! I was induced but not due to weight.

rainbowstardrops Tue 26-Apr-16 07:41:03

They're very inaccurate! My old boss (a Dr!) was told her fourth baby was measuring way too small. She had numerous tests and scans etc and they worried her stupid. They eventually decided to induce her two or three weeks before her due date because they suspected the placenta wasn't feeding the baby anymore.

She was told the baby would be quite tiny and need interventions but she delivered a beautiful 6lb something healthy baby that was absolutely fine - (6lb odd at 2-3 weeks early!)

It's all a load of codswallop smile

Nicky333 Tue 26-Apr-16 08:09:13

I had a growth scan and the consultant told me they can be out by up to 20% each way. I think it also says that on the scan sheet in my notes.

superwormissuperstrong Tue 26-Apr-16 09:07:20

Thanks all for your experiences - I'll keep going to my scans and rereading this and hopefully it will keep the anxiety down.
The consultant was very wishy washy and did not inspire me with confidence which is why I spent some time when I got home looking thoroughly at the sonographer notes and all the different measures and was surprised that they seem to be calling me back on the basis of one measure when the rest are tracking and that the weight measure is known to have such variation. (I know about stats and confidence intervals from my job so it seems strange that he focused so much on such a small change in one number...)
Thanks again

SouthDownsSunshine Tue 26-Apr-16 09:10:08

Inaccurate! Had a small bump, at measuring scan was told baby would be 8lb. Dd was 6lb7oz.

They were accurate about her head being big. It was. She was all head and a scrawny body.

Icklepickle101 Tue 26-Apr-16 09:10:48

I had a scan on the 14th saying baby weighed 6lb6 and DS was born on the 16th weighing 7lb13 so all the tiny baby clothes I'd rushed to buy didn't fit hmm

SunnyDays1987 Tue 26-Apr-16 09:11:36

I was told DS was mid 4lb at 36 weeks. He was born 2 days late at 5lb 5oz so they can be very inaccurate at the bottom end too!

NoCapes Tue 26-Apr-16 09:15:34

I was told a week before my due date that DD was 5lb 4oz
She was born at 8lb

So not very reliable IME

mmmuffins Tue 26-Apr-16 09:21:46

I had a scan at 38 weeks which estimated baby was just under 6lbs. She was out at 39 weeks and was 6lb 4oz.

Timetogrowup2016 Tue 26-Apr-16 09:52:39

At 34 weeks baby was said to be 5 pounds 5 she was born at 5 pounds 1 at 35 weeks so quite accurate in my case

Tinselmouse Sun 01-May-16 19:37:21

Had a growth gran at 39 + 1 and was td 5lb 5oz. Born at 39 + 4 and was 5lb and 6oz - sp pretty accurate in my case!

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