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Pregnancy

Talk about every stage of pregnancy, from early symptoms to preparing for birth.

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Original poster

Estimated baby's weight during scan versus actual birth weight

61 replies

TransatlanticCityGirl · 28/12/2013 05:20

I'm wondering how accurate a sonographer's estimate of a baby's weight is during a late pregnancy scan... every single time I hear of a scan being done to estimate the size of the baby it is WAY off and I've heard multiple accounts of women being advised to be induced or have a c section due to babies who are thought to be large, but actually they are several pounds lighter than estimated.

My DD was 9lb 10oz which was a surprise - I was measuring perfectly average so midwife never referred me for a scan. I ended up with an EMCS. I suspect that my 2nd baby will be larger as he was measuring (at both 12 and 20 week scans) to be a week older than is biologically possible.

I'm worried that towards the end of my pregnancy I will be advised to have an ELCS due to baby's potential size and wonder if they will want to estimate via a scan?

Looking to hear what other mothers have experienced before....

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Flickstar · 28/12/2013 09:17

I was induced at 39 weeks due to pre eclampsia. I was scanned right before I was induced and the baby's weight was estimated at 10lbs 4ozs. He was born a day later at 8lbs 10ozs!

Froblawd · 28/12/2013 09:20

I measured big so had an extra scan at 31wks where I was told the baby was already 6lbs so I should expect him to be at least 10lbs at birth. I went 14 days overdue so was terrified at the thought of a potential 12lb monster. He arrived at 7lbs3. Somebody got it wrong! And I had very little in the way of waters do they couldn't blame it on that.

GeeinItLaldy · 28/12/2013 09:23

Scanned on my due date and estimated weight was 7lb 11oz. Scan was done by consultant rather than sonographer as it was a routine consultant appointment. Baby born 11 days later weighing 8lbs exactly so fairly accurate in my case.

BunnyBaby · 28/12/2013 09:24

My Ds2 was scanned at 40 at 10lb and born at 40+11 at 10lb 1 - pretty accurate. My friends DS1 was scanned at 9lb7 and was 7lb, so can be hit and miss.

BabyStone · 28/12/2013 09:26

I was scanned at around 38-39 weeks, predicted weight 9-10+ lbs, ds weighed 8lb 2

mrsminiverscharlady · 28/12/2013 09:27

I had growth scans every 4 weeks during my last pregnancy as there were concerns about his growth. In the end he was bang on the 50th centile and predicted to be about 7 1/2 pounds. He was 10lb 13oz!!

nomoreminibreaks · 28/12/2013 09:32

I've heard a lot of similar stories but have wondered if they're just the ones that stick with people/are worthy of note? DS was in the 98th centile at 20 weeks and also when he was born 2 days before his due date (9lb 11)

Bearfrills · 28/12/2013 10:14

I had well-being scans every four weeks from 24wks onwards when pregnant with DS as I had several episodes f bleeding bad enough to need admitting to hospital. One of the things they kept an eye on with the scans was his growth. He was always measuring on the larger side and at my last scan at 39+2 they estimated him to be 8lb 8oz. I went into labour at 39+5 and he was 9lb 3oz so they were quite close.

With DD I had a scan at 40+3 when I was in early labour. I'd been niggling on so went to the community MW for a sweep to try and move things along, she thought DD might be breech. Off to hospital, got a scan and she was. We decided to try an ECV so they did an HD scan first to check whether it would be possible. It wasn't but they completed the scan anyway including measurements and estimated weight. This was a crystal clear scan, so clear we could see each individual finger and toe, and done slowly with no rushing. They estimated 9lb. She was born by EMCS half an hour later and was 7lb 10oz :)

ThurlHoHoHow · 28/12/2013 10:18

Estimated a little 6lb baby - had an 8lb baby! Everyone was surprised, they didn't know where she had been hiding

PacificDingbat · 28/12/2013 10:21

Notoriously unreliable and v user dependent - AFAIK up to 30% discrepancy between estimation and actual weight.

The overall weight is not half as important wrt to the mode of delivery as the size of the head, baby's lie and presentation, shape of pelvis etc.
Don't focus on the weight.

Tea1Sugar · 28/12/2013 10:23

At 38 weeks I was told baby was measuring 8lb 9oz. She was born at 42 weeks weighing 8lb 3oz!

WeeTeaJenny · 28/12/2013 10:52

My scans were coming up big and I had excess amniotic fluid so they were thinking it might be gestational diabetes and to prepare for a large baby... in the end he was 8LB , only 1 ounce heavier than his brother so all that panic for nothing... take the scans with a pinch of salt xx

Knakard · 28/12/2013 10:56

I was scanned at. 41+2 estimated very small baby 5/6lbs. delivered 41+6 she was 8.2lbs

banana87 · 28/12/2013 11:01

Baby scanned at 36 weeks to be 7lbs, advised she was going to be huge so had induction 2 weeks early and she was 8lbs 6oz!

chutneypig · 28/12/2013 11:03

I was scanned three days before my section, which was 37w6 - they estimated both twins at around 8 lb. One was 9lb 2 and the other 5 lb 10. They said the smaller one had been lying at an oblique angle so they'd measured her abdominal circumference larger than it was.

Ilovekittyelise · 28/12/2013 11:10

i have type 1 diabetes and i swear they routinely over measure (expectational bias). i keep my diabetes extremely tightly controlled so no reason to expect whopping fat baby; my last scan at 32 weeks i could see the line measured for AC was ridiculously slack and lo and behold baby estimated 90th centile. he wont be. next scan in a week i plan on asking for photos of the measurements to discuss with consultant to prevent the biased measurements impacting mode and timing of delivery.

son was estimated 8 pounds 9 @ 39 weeks. born at 39+5; 7 pounds 8.

hotair · 28/12/2013 11:28

This reply has been deleted

Message withdrawn at poster's request.

CoffeeQueen187 · 28/12/2013 11:32

Ds1 - I was told he was v. Big. Turned out he was 7lb 14 and I had an extra placenta (should've been a twin)

Ds2 - I was told he was small and I was carrying a lot of water. He was born at 10lb 6.

Ds3 - I was told he was average and I was meaUring right through the whole pregnancy. He was 8lb spot on

30SecondsToVenus · 28/12/2013 11:45

I was measuring really big so went for a scan at 34 weeks. Baby was estimated to be about 11lb. I was

She was born weighing 7lb 14oz so not as bad

FortyMerryFuckers · 28/12/2013 11:49

My sister was told through out her pregnancy that they were worried about the size of the baby as he was so small they were scanning her weekly and they had all the paediatricians and NICU on standby for the baby when he was born weighing 9lb 10oz

FortyMerryFuckers · 28/12/2013 11:52

They were estimating 4lbs

DuPainDuVinDuFromage · 28/12/2013 12:25

I was induced on my due date because dd was small for dates all through my pregnancy and we had lots of scans and consultant care for this reason. When she was born she was a middle-of-the-range size and certainly not small enough to warrant the early induction. I don't think they can be at all accurate with the scans!

Mrsantithetic · 28/12/2013 13:22

I was told I was having a big baby. She was 6 pounds.

Mumlar · 28/12/2013 13:28

During each of my three pregnancies I have been looked after by a consultant. For my third I had a very senior consultant who scanned me a lot. He said that scanning was an imprecise science and felt that the weight of my previous babies was far more relevant. He was right in my case. My babies weighed 8lb 13, 9lb and 9lb 2oz, so give or take a few ounces they were all about the same.

Casmama · 28/12/2013 13:29

I was induced due to being small for dates- estimated 5lbs 13 and DS was born next day at 5lbs 9 so pretty accurate in my case.

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