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Original poster

Estimated fetal weight on scans - how accurate?

30 replies

Solero · 07/06/2013 22:43

Am 31+5 with #2 and had a growth scan today as am type 1 diabetic and baby's estimated weight was already 6.2lbs. My diabetes has been well controlled for most of the pregnancy (last HbA1c was 6.8) but sugars are starting to climb quickly now. I am a little worried that she is already quite large altho midwife says bump is normal sized and the sonographer didn't seem overly concerned. So how accurate are these measurements?

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Signet2012 · 07/06/2013 22:45

They said I would be having a baby between 8.3 and 8.8 pounds. She was 6 pounds.

So in my case - not very!

LaChaiseVerte · 07/06/2013 22:46

Not at all in my anecdotal experience - to the point that it seems odd that they even try!

Original poster
Solero · 07/06/2013 22:48

Well with number one I had a scan at 36 weeks where they estimated 7lbs and she cam out at 6lb12 so was quite close to actual weight which got me a but worried. But I guess its not an exact science when they are wriggling around and bouncing up and down in there Smile

OP posts:
Locketjuice · 07/06/2013 22:51

My '4lb at the most' baby was 6lb 5oz

Snowflakepie · 07/06/2013 22:57

My SIL who developed gestational diabetes and was classed as obese was told at 36 weeks that both of her babies would be well over 9lbs. 7lbs 7 and 7lbs 8. I don't think they can tell a darn thing tbh.

ElfOnTheTopShelf · 07/06/2013 23:08

They told me DS (my second pregnancy) would be big, but I dont think they expected him to be as big as he was when he was born (length, not just weight). I had a c-section with him and they had to use forceps because he was so wedged in.

But they told me that my DD (first pregnancy) was going to be 7lbs and she was 8lbs 13.5oz so I'm guessing it isn't an exact science :D

WillYouDoTheFandango · 07/06/2013 23:17

Mine was estimated at 7lb 4oz on Wednesday and was born at 7lb 4oz on Sunday Grin I saw the sonographer a few weeks later and congratulated her on a job well done.

madamginger · 07/06/2013 23:25

They told me ds2 was 10.5 lb and he was 7lb13oz so not very!

MrsMargoLeadbetter · 07/06/2013 23:41

Experience of friends would say not. Mainly estimated large babies who them turned out average. Better than the other way around Shock I guess.

I do wonder how big/current the sample date is. I cannot imagine that the date from my growth scans and then baby weight goes into a database anywhere....?

I am due in 1.5 weeks last scan suggested 8.5, we shall see.

MrsMargoLeadbetter · 07/06/2013 23:42

And sorry to hear

MrsMargoLeadbetter · 07/06/2013 23:43

you are concerned OP. Will you have another at 36 weeks? Bump size might be fluid rather than baby?

Areyoumadorisitme · 07/06/2013 23:50

Proven not to be very reliable, I did look into it the time but it was a long time ago.

DS1 was estimated at scan to be 10lb, he was actually 9lb 1oz. DS2 was estimated at between 8 and 8 1/2 lbs and was actually 10lbs 2oz.

LittleFrieda · 07/06/2013 23:54

I was monitored because they were worried DD was small for dates. She was born at 39 weeks weighing 8lbs.

jessw25 · 08/06/2013 06:38

Good friend had late scan as she was very big - was told to expect 10lb baby (!). Baby was 7.5lb when born..

Fairy130389 · 08/06/2013 11:19

I had a growth scan at 36 weeks, and was told DS was around the 6lb mark then. I asked at the time how accurate this was and sonographer told me within 10% each way - I have heard countless stories of women though who were told wrongly!!! I think it is just a case of wait and see - if they aren't concerned, that is a good sign.

Wildwaterfalls · 08/06/2013 11:25

Not very accurate for us. Had a scan at 36 weeks putting DDs weight at over 3kg, she was born a week later weighing 2.8kg.

BubaMarra · 08/06/2013 14:30

Mine were quite accurate. With DD1 the scan overestimated by 300g and DD2 was underestimated by 200g.

neversleepagain · 08/06/2013 19:37

The day before my c section the sonographer said my twins were...

Twin 1 - 5lb4 (she was 5lb4, so spot on)
Twin 2 - 6lb1 (she was 5lb8)

Not too far off.

TheFallenNinja · 08/06/2013 19:40

It's a bit like guessing pennies in a jar.

TicTacSir · 08/06/2013 19:46

4st of pregnancy weight each time (I'm 5'1") produced DS 6.3 and DD 6.11 - I was told DD would be big. No, all fluid.

ThistleDown · 08/06/2013 19:46

My "not even 5lbs" baby (at 38 weeks) was 8lbs when delivered a week later.

omama · 08/06/2013 21:22

At 39wks sonographer estimated 7lb 2oz & 4 days later he arrived 7lb exactly. Pretty close!

MrsSpencerReid · 08/06/2013 21:26

I'm t1 too, DS was estimated at just under 3kg at scan 10 days before he was born at 2980g (6"9) at 35w. It's so hard keeping sugars in control at this point Hmm good luck Smile

CunningAtBothEnds · 08/06/2013 21:28

About as accurate as me giving you the lotto numbers!! DS1 was "going to be at least 9lb" due to GD (scanned every two weeks) - didnt buy any newborn clothes really... Out pops 7lb 3.5oz dink! Same again with DS2 (born in Dec) was "going to be big" again due to GD, to the point that they agreed to give me my ElCS at 37+6... I was prepared this time had tiny clothes... 6lb 2! Teeensy! Had to get him prem hats!

The scans are based on head circumference and MM difference make huge difference to weight proposal.

messmonster · 08/06/2013 21:31

Consultant obstetrician said my DD would be around 1.9kg and she was 1.95kg Smile Midwives were stunned that the estimate was so accurate so based on that I think it's unusual for them to be so close. Good luck Smile

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