How accurate were growth scan percentiles compared with your baby’s birth weight?

[Shopaholic100]

What percentile did you measure during pregnancy and how much did your baby weigh at birth? Just intrigued to see how accurate the measurements are.

First baby I can't remember the estimated centile, but estimated weight at growth scan was 3.7kg. he was born a couple days later at 3.71kg so bang on accurate with him.
2nd baby on growth scan measured about 3.2 kg but was born the next day 4kg, so was quite off.
I had a friend off the opposite way. She's diabetic and they thought baby was about 8lb at 36 weeks. Baby was born at 37 weighing 6.5lb!

Growth scans were fairly accurate. Fundal height measurements not so much, especially with ds4. I measured 52 weeks at my 34 week appointment and he was born the following week weighing 7lb 2oz.

I remember with ds3 his predicted birth weight according to the charts was just under 9lb. The dr insisted he would be 10lb at least but I thought he would be 8lb 12oz and 53cm long. He was born at 40+2, 8lb 12oz and 53cm long. Still quite proud of that guess and he is 15 now!

In the early 90s I was told tiny baby (which surprised me as I am 5’10 and dad was 6’5) I was admitted to hospital wearing my mothers size 12 jeans at 42 weeks I had a 9lb12 baby who was 64 cm long… with a massive head. Horrible delivery- blood transfusions- stitches- infections etc- finally cauterised - awful.

i was told dd2 was predicted to be 11lbs + at full term - said I would not have a natural birth under those circumstances and was told I could have an elective - they were born at 42 weeks. In less than half an hour beginning to end with not a mark on me. 9lb8.

3rd was easy (considering) also big - I tried not to think about it.

Can't remember the centiles at all, but the weights were fairly accurate.

DC1 was estimated 6lb15 at 36 weeks. Born a week later weighing 7lb5. DC2 was estimated 7lb12 at 36 weeks (not a growth scan, but my trust do a 36 week/positional scan as standard). Baby was frank breech (previously undiagnosed!) so the sonographer estimated actually a little bigger. Born nearly 2 weeks later weighing 8lb1.

On average babies put on about 1/2lb (8oz/430g) per week in the later weeks of pregnancy. So yeah. Pretty accurate.

I dont recall being told percentile during the pregnancy. But at 39 weeks was advised baby was 3.9kg, so projected to be over 4kg by term, depending on how far I went over could be a good bit more. Arrived bang on due date 3.5kg.. so definitely take the measurements with a pinch of salt! Can be 20% off, either under or over estimated.

Mine were very accurate. DD1 was dropping down the centiles and at 37w was predicted 9th centile. She was born at 38w and was 2.6kg (7th centile). I can't remember the exact centile DD2 was predicted, but it was between the 10th and 25th line on the chart at 36w and she was born at 39+3 and was 2.8kg (17th centile).

I've anecdotally heard that weight predictions are more accurate for smaller babies than when predicting big babies, but i dont know if that is backed up with fact.

This thread will attract more people who had inaccurate growth scans than people who had accurate ones, and therefore don't feel they need to tell their story!

For me: one baby's was accurate. The other baby was about 10% smaller than they said. Growth scans for both.

It's well known that there's a 20% margin of error. But if you have the same sonographer for multiple scans, it does give an indication of growth rate, which is in many ways more useful than the actual weight estimation.

Way over with my daughter. She was predicted to be 8lbs but came out a dinky 7lbs 1oz. I had loads of growth scans for a variety of reasons with the last one being at 40 weeks four days before she was born.

I was told my son was at the 90th percentile at a growth scan and was encouraged to have an induction before he got too big. After a horrible induction experience he was born at 39 weeks, 7lbs 4 ounces which was the 49th percentile and not remotely big. I’m still annoyed about it nearly 3 years later.

Neither of mine were accurate! Baby 1 I was told was 97th centile, last scan said she would be 9lb born and she was 7lb 14oz. Baby 2 was measuring huge from 32 weeks and at my 38 week scan was measuring at 9lb 8oz so I was advised to have an induction literally the next day because they say once over 4.5kg the risk of shoulder dystocia increases massively for a vaginal delivery so it was induction or c section, I opted for induction and he was 8lb exactly born.

Very accurate for me. Told 6 pounds and she came out bang on 6 pounds.

I'm due another in a couple of months so we'll see if it's accurate again.

Not even remotely accurate. Lots of growth scans all over the place. One 2 weeks before birth on 20th centile. A scan day before birth showed a 7lb baby at 41 weeks. Baby born at over 9lb, 80th centile...

I could feel was bigger than they said though from positioning. I'm tall and his bum was really right up top of a very large bump and head was really low. He did come out very long as I said.

100% not accurate in my case.
DS was predicted slightly above average - came out at around 15th centile.
DD was predicted extremely large due to GD - came out again low centiles (can't remember exactly what) but was significantly under what they expected. She was 7lbs 1oz.
Only explanation was they had long legs which put the weight measurements higher.

I never had any growth scans and they never knew my baby was going to be so big he was born 11 days overdue and was 10lb 6 currently pregnant with my 3rd and they have told me I’ll have to have additional scans etc now due to the last size of my previous baby!

I can’t remember percentile but for various reasons I was scanned 17 hours before DD was delivered.

on her scan they confidently told me her weight was 7lb exactly . She was in fact 5lb 13oz

I had regular scans due to Gestational diabetes.
I can’t remember percentiles but they predicted her weight would be 6lbs 6 ounces on a Friday two days before due date. She was born two days later and weighed 7lbs 7ounces.

I was told DD would be 8 1/2lbs or 3.8kg. She was born two weeks late at 6lb 4oz (2.885kg).

Rubbish for bit of mine. I was told that my daughter was over 9lb at 40 weeks, she was a week late and 8lb 1. Similar with son and he was 7lb 12

Can’t remember the percentile but DS was predicted to be big so in conjunction with my age (40 when he was born) consultants recommended planned c-section. I resisted and ultimately had a drug free vaginal birth of a 6lb 6oz baby.

He’s almost off the scale in height and weight now he’s almost 2 mind you!

Just gone back and checked. He was the 38th centile at birth, but 90th by his first birthday!

Way off. 90th percentile through pregnancy, warned it was going to be a big one but he came on due date and was 45th percentile. The measurements were designed to pick up small babies and are less accurate for large ones

Completely wrong. DD they kept saying was a tiny baby, like 5lb something. She came out bang on time at 8lb 7. DS they kept saying would be a whopper - he was 1 day early and was 7lb 12

Thanks for sharing, it’s so interesting to hear about everyone’s experiences. My friend’s baby is on the 50th centile, so we were just trying to predict how much baby might weigh, it doesn’t matter but I was thinking probably about 7lb. My friend is really petite so it’ll be interesting to see how big baby is.

I think my first DD tracked on thr 50th percentile, she was born at 40+5 and weighed 7lba 6oz, my second i think tracked along the 90th percentile and she weighed 7lbs 10 at 39+5

I’m very petite they thought my first was going to be tiny but was average, thought my 2nd was average and she was a whopper.