If they're so inaccurate, what's the point in growth scans??

[Munchkin30]

Hey all,
I'm 37 weeks and had my final growth scan today. They estimate baby's current weight as 7lb 2. My dd was born at 42 weeks at 6lb 9 with a 3rd degree tear and forceps and was 4th centile whereas currently this one is nearly 90th centile. Everyone I've mentioned it to, and everyone on a quick google search, says these scans are wildly inaccurate (like not within a lb inaccurate but lbs out either way)
I asked the sonographer today how accurate it is this late and she said all the measurements line up so she's pretty confident!
So what do I believe?? And what's the point in doing them if there SOOO inaccurate??
Thanks all xx

 

[Becky1987]

Are you measuring big this time? I had a growth scan at 28 weeks and baby's estimated weight was 3lb 3oz!! My son was born at 40 weeks weighing 7lb12 on the 45th centile and thia baby is of the charts! I'm due another scan at 32 weeks but just wondering what they will do? Are they just going to leave you to go naturally? X

 

[Munchkin30]

The only reason I'm having growth scans is cos my daughter was so small. The belly measurements are bang on or a week under. At 28 weeks it was just under 50th centile, 33 weeks just over 50th and now it's nearly 90th so from worries I'd have another small for dates baby it now looks big!! They've just said there's no concerns about the weight now, to see the midwife weekly and she's to do a sweep at 40 weeks then induction at 10 days over if necessary.

 

[wanting2010]

I wonder if a lot of it has to do with the person doing the ultrasound or the baby's position. Or maybe if there's not a follow up ultrasound to recheck, maybe the measurements at the initial scan were off. They were pretty accurate for me with DS. At my 32 week scan they estimated that he would be 8-8.5 lbs and he was right on 8.5 lbs at 41 weeks, so probably reasonable to assume he would have been pretty close to 8 lbs at 40 weeks.

I had a growth scan at almost 33 weeks this pregnancy and baby was measuring between 5.5-6 lbs and in the 92nd percentile, so I had another scan at 35 weeks to recheck. Baby was measuring in the 97th percentile at over 7 lbs at that one, so the measurements have been pretty consistent. They are going to continue checking her growth from here on out.

 

[AmeliePoulain]

I have growth scans due to GD, mine have always been very accurate. Within a few ounces.

My sonographer tries to take each measurement 3 x to get a good average.

What can be inaccurate is the formula they use for getting weight from just head, tummy and leg measurements. It is a best guess as it doesn't take account of a chub baby or a muscley one.

 

[Feronia]

There really is no point for exactly the reasons you specified. My midwives don't recommend them at all.

 

[Ecoden]

As someone else said I think it's the formula that's not accurate. They told my sister that my niece was measuring around 7lbs 2 oz and she ended up actually being 9 lbs. Quite a shock but she had a vaginal birth with her. I don't get why they do these either.

 

[slongson]

I was told my daughter was 5.4 at 34 weeks at 34 +2 when a he was born she was exactly 5lb 4 oz so for me was pretty spot on x

 

[AmeliePoulain]

I think what helps is if you have them regularly and from earlier in pregnancy than 30+ weeks. That way they can see if baby is following a curve and it is unlikely you would have 3 or more completely inaccurate scans.

With a complication like GD I feel my growth scans have been very worthwhile - I feel happier too that the cord blood flow and placenta and fluid are checked for me. When DD1 my GD wasn't diagnosed until very late and my 36 week scan with her wasn't that accurate. With DD2 though I had 4 scans and her weight plotted exactly on a curve, same with this baby.

DD2 was estimated 7lb 8oz and was born 7lb 7 1/4 oz so very very spot on!

 

[Munchkin30]

Thanks Amelie. Yes I had one at 28 weeks and baby was just below 50th centile. At 32-3 weeks it was just above 50th but now at 37 it's at nearly 90th centile so I'm a bit suspicious!! Also I looked at the measurements on the internet and the abdomen is 88th centile and femur length 25th centile, they couldn't get the head cos it's too low. But they still put baby at centile of abdomen measurement?? Tbh I think it's somewhere around 50th centile. Much bigger than dd but not huge. I'm only 5ft 1 and put on about 23lbs of bump so I don't think it can be massive!!

 

[AmeliePoulain]

If they couldn't get the head circumfrence or width then I would basically discount the scan!

 

[Munchkin30]

They couldn't get the head at all! Totally wedged. Well I'll not pack the tiny baby clothes away yet then! It'll be interesting to see!!

 

[Perplexed]

My dr is sending me for a growth scan but I don't think the purpose is growth. She just wants to see the blood flow through the cord, condition of placenta & fluid level. My old dr used to do an ultrasound at every appointment while my current one only did the one at the beginning to confirm the pregnancy and so far this is the 3rd u/s she sends me to.

 

[AmeliePoulain]

I had an interesting experience at my last scan - a doctor who was new to the hospital was sitting in and he had experience of scanning but wanted to 'play' with the machines.

The sonographer did my scan but then the doctor had a go at all the measurements. The tummy measurement can really easily be quite out because I didn't realise they are scanning to see a very specific part of the tummy - the doctor kept accidentily including a measurement that factored in my baby's kidneys which made it a bigger measurement. The sonographer showed him how tricky it was to get just the right cross section.

She said it gets more and more difficult the baby is too.

 

[Loozle]

I don't think they are always inaccurate. I had a scan with my DD at 36 weeks and they estimated her to be 6lbs exactly at that point. She was born 1 week later weighing 6lb 3oz.

 

[mum140381]

mine where all spot on x

 

[Insomniash]

This is going to sound quite cynical, but I think unless there is a justifiable medical reason to assume the growth may be a concern (such as gestational diabetes, iugr etc...) I feel like these growth measurements are just a testament to the over medicalization of child birth.

They cause unnecessary concern and medical intervention (induction and c-section). I have heard so many stories about women being told they are having a huge baby (9-10 lbs), only to agree to an early induction and end up with a very small baby (5-6 lbs). I honestly feel that this is doing babies an injustice, if all is well let them grow! My baby is growing just fine, not too small, not too big, and yet I had an OB try to send me for three more growth scans before I am due and she couldn't provide me with a proper reason. I fired her

 

[Feronia]

I 100% agree, Insomniash. That's why I skipped scans during this pregnancy.

 

[Munchkin30]

I didn't have any scans last time but dd was below 4tu centile and born at 42 weeks. I suspect she wasn't getting what she needed because when she came out she was very long and skinny with loose skin and I'd been losing weight so this time I was glad to be offered the scans. If they wanted to induce early or do a c section because of them though I'd be questioning it pretty vehemently.

 

[Rhi_Rhi1]

I think they are funny things... they never seem to be apot on; with my first they said i should expect a small baby 5lb ish. He was 7'7 which i believe is very average with my first they tole me he was a larger baby and to expect a baby closer to 9lbs. He was infact 9lbs...