How accurate are baby measurements when pregnant?

[NotLongToGoooo]

I'm 38+3.
I'm due to have a c section next week.
Baby has always measured bigger but just within normal range.
They've done another scan today and have said she's on the 99th percentile (8lbs 4). Therefore tipped slightly over the 'normal' range.

I'm wondering how accurate the measurements actually are as I've heard different stories from people who have said their baby was a completely different weight to what was predicted from scan measurements etc.

They're saying they feel it's safe to wait until the c section date next week as I will be a few days over 39 weeks by then, and they prefer to wait until after 39 weeks so their lungs are fully developed.

I was told my baby was small because my bump wasn't meeting the lines.
Then to big then to small
Growth scans too but she came out a good weight she was 6lb 6oz 😍

When I had a growth scan 36+6 I was told it isn't very accurate but it's the most accurate way they have. I was told it can be a pound different either way and it is more difficult to measure further along you are.

Ideally you want to wait for as long as you can.

In my experience I was told I had a massive baby and to expect a very large baby on multiple scans we are talking 9/ 10 lbs which was surprising as I'd already had 2 that were very small both under 6lbs I even took all my tiny baby clothes back and swapped for bigger sizes then gave birth full term to a 7lbs 1oz baby and had clothes which were far to big

I was told I was having a big baby. She came at 40+2 and was 6lb4oz! Tiny!

Mine was pretty spot on from both the fundal measurements and a growth scan at 36 weeks by consultant. Ended up going to 40+12, EMCS unrelated to size, was 9lb 1, and continues to be up in the 98th centile at 4 weeks old

I was told my DS was going to be about 7lb. He was 8lb 9oz.... 😂

Aw hope the clothes fit! Mine was in Next size 'up to 1 month' for her first outfits and they fit perfectly. The M&S 'newborn' size fit when she dropped a bit of weight (went down to 8lbs 11oz) in the first week.
You'll be fine waiting for when the Consultants say, enjoy the last bits as much as you can.

Mine was predicted to be on the 50th centile from about 26 weeks - at 38 weeks I was given an estimated birth weight of 7lb5oz.

He was born at 40+1 weighing 8lb13oz 😂

Don’t listen to the consultant about the clothes they will be fine I had my baby 4 weeks ago was predicted 8lb 8oz for delivery at my last growth scan and came out at 10lb 15oz so hugely off and newborn still fitted him for a week so I think they will fit your baby for a while longer even if there predicted weight is right. good Luck

Measured 9lbs - born 10 lbs 9

Was told my girl was gonna be 7lb something. She was 9lb 6oz. Got stuck, shoulder dystocia, respiratory distress from being stuck, in hospital for a week afterwards. I tore, had a cut, multiple stitches oh and I haemorrhaged. Really wish we'd have known a measurement closer to her actual birthweight and maybe if we/hospital had that knowledge none of that would have happened 🤷‍♀️ 😔

I don’t know how accuarate they are.

Im pregnant with baby no 3 and think he’s gona be a big one. (9 1/2 - 10lb). My consultant still wants to wait until 39 weeks and will have a consultant deliver him.

ps my dd was 8lb 4oz and she was in newborn for a good few week. Ds was 8lb 13.5oz and never fit - he was in 3-6 months at 6 weeks.

My baby was 8lbs 4oz and fit into 'tiny baby' clothes for about a week. Unless you birth a titan, you'll probably be okay😊

Can I ask how these predictions are made? The trust I'm at doesn't use centiles, which I actually quite appreciate as women I know from out of area have regularly been told they're about to have a porker in the 99th and then they end up with an 8 pounder. So I'm actually quite glad that I'm not getting stressed by that. However I'm 37+3 and would quite like to know what to expect! My fundal height has matched the week for the past 12 weeks - does that mean 50th?

Measurements decent with my dd but with DS they were way out - they measured him as 91sr and he came out 25th - only 4 days between scan and delivery. We were like ‘where is the rest of him?!’

the sonographer told me that they reckon their measurements are 25% accurate on the exact day they are taken. So the sonographer do not think they are very accurate either!

They don't do centiles pre-birth. They do it based on measurements so measuring bone lengths, head circumference etc then have a chart that suggests what size the baby will be when born if they follow the same path as size as current gestation, if that makes sense

Not very, but they're the best they can do!

They're also influenced by human error - there's some degree of professional judgement about how exactly they draw those circles and lines to measure heads and abdomens and femurs. My consultant actually said to me that they generally err on the side of caution, so there's an extent to which if they know they're checking whether baby is big, the lines and circles get drawn to be a bit on the big side, and vice versa if they know they're checking whether baby is small. This makes sense as the last thing they want to do is miss something.

I'm constantly being told what centile my unborn baby is on, so some places are definitely using centiles.

@TeddyBeans
Oh good! I think we went overboard and bought too many. So I'm hoping she'll get use out of them!

@Stag82
Aww! This is what I was thinking. I've no idea what she'll weigh when she's born so we've packed newborn and lots of 0-3 months.
The consultant said she wouldn't bother with the newborn stuff as she likely won't fit but you never know so I'm taking them anyway. And she'll probably be in 3-6 months in no time! 😂

Same. I’m having growth scans because baby has “dropped two centiles on the abdominal circumference charts”, quoted from my consultant at hospital. Centiles are definitely used on unborn babies.

Dc1 Predicted 3lb.2 born. 5lb
Dc2 predicted 5lb.3. Born 7lb.4
Dc3 predicted 9lb 8 born 7lb . 2

2 and 3 were growth scan predicted
IME they are nothing more than shit guess work !

Not at all! Tonnes of growth scans due to bump size, but he was always the 90th percentile on all the scans, expected to be 9lbs, came out 40+1 as a dinky 7lb 9oz 😂! I asked them to double check while still on the theatre table haha!

There’s no need to bring your section forward in the absence of other risk factors for a large baby though, you could wait until term or longer as the risks are with vaginal delivery.

For my first they were spot on. Last growth scan at 38 weeks predicted 8lb 3oz. Born 3 days later just over 8lb 3oz. For second they were a bit off. They kept telling me this baby was definitely smaller than my first. Born 8lb 13oz at 38 weeks