Estimated baby's weight during scan versus actual birth weight

[TransatlanticCityGirl]

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....

[stopgap]

I have GD and so am having scans twice a week now to monitor fetal growth. I'm 35 weeks, and he is measuring 4.8 pounds, so definitely on the smaller end. Every scan I've had (I think five so far) has indicated that he is small, with a projected full-term weight of around 6.5 pounds. We'll see. I am taking the results of these scans with a huge fistful of salt, given that so many accounts indicate a huge margin of error.

[littlemisssarcastic]

I was told my baby would be small for dates. Hospital estimated 4lb and induced me. DS was 8lbs when born 36 hours later. He was also very long and had a 36.5cm head circumference.

[3bunnies]

Scanned at 39+3 as measuring small - was estimated at 8lb, induced due to low liquid and born next day he was 8lb 12oz!

[purplebaubles]

Scanned at 35 + 5..estimated to be 6lb 4

Gave birth at 36...baby was 6lb 5.

Pretty spot on I'd say!

[princesscupcakemummyb]

with my 1st baby i had regular growth scans due to measuring larger then normal i had alot of increased waters from 26 weeks aswell anyway the consultants worried the crapper out of me all the way through telling me she was going to be a 10lb baby i cried at the thought she was born at 40+5 weighing in at 8 pounds 5 so not as big as originally thought the weight estimates are very off their not a reliable source really its just an estimate

[ROARmeow]

Two DC's, both measured via scan at 36 weeks and they estimated correctly to within an ounce.

I was very impressed!

[flossieflower]

Had a planned c section at 39 weeks as bump never got over 34cm, scans reckoned baby was 5lb with hardly any fluid and a tiny head and possible learning difficulties from this. Had paediatrician in theatre ready to resuscitate her- she was 7lb 3 with plenty of fluid and an exactly average head circumference. Midwives and paed were stood there with nothing to do!! I was rather cross though that my plans for a home birth were shelved for no reason.

[Hopelass]

DS was estimated at 9lbs but was 7lb6oz at birth 39+4.

[Inglori0us]

I had a growth scan at 34 weeks and was told to expect a big baby. Sonograph said dd was already 7lb. She was born at 38 weeks weighing 6lb12 but she was very long (58cm) so I think that's what they do the calculation from.

[hubbahubster]

Scan at 38 weeks estimated DS was close to 8lb already. Delivered by CS at 39 weeks, 6lb 13.

[neversleepagain]

I was scanned at 34+4 with my twins.

Twin1 estimate 5lb4 actual 5lb4
Twin estimate 5lb8 actual 5lb8

Babies born at 34+5, spot on.

[madwomanintheatt1c]

Dd1 scanning at 9lb 13, told she would be up to a lb heavier. They insisted I had a CS as a result. She was 8lb 6.

For the other two vbacs I have no idea what size they predicted as I didn't listen to a word of it. Load of old cobblers, and we are so desperate to believe in science we swallow it whole.

[Flisspaps]

DS was estimated to be 9-10lbs.

He was 11lb 7oz, born at 40+1 (spontaneous, attempted unsuccessful Homebirth)

[purplemurple1]

Scanned about 10day's before the birth and weight estimated at just under 3kgs. He was bang on 3kgs. So very accurate.

[Linnet]

I wasn't scanned late in the pregnancy but at my 1 week overdue appointment I asked the midwife how much she thought the baby would weigh and she said about 8lbs. I was a bit shocked as I'm small and dd1 was only 6lb 9oz. I went into labour that night and when dd2 arrived she was 7lbs 12oz so very nearly bang on the prediction.

[Mogz]

I was scanned at 36w and baby was estimated to be 6lb 4oz at that point, she was born at 40w+8 at 7lb exactly, so I think they were just a little off.

[ilovesmurfs]

I had extra scans with my firs three as I measured small, they said 5-6lb.... Ermm nope 9lb 3oz, 9lb 5oz.

With ds4 they tried to say the same!e thing, rather the consultant did, the midwife said he was a good sized baby, consultant disagreed and said he was small. He was 10lb 13oz.


No 5 they said was big, I said no as I cpudl tell she wasn't as big as the boys had been, scan the day of labour they said 9lb+ and that I woidl need a c section as I am small, I did point put I had had all four boys vaginally an ds4 was born in birth pool! Apparently I was 'lucky'...

Anyway dd born after three hours labour 8lb exactly, positively tiny for me!

[lemonpoppyseed]

I had a scan at 38 weeks because my belly hadn't gotten any bigger since 36 weeks. All was fine, and estimated baby weight at birth was 8lbs 8oz. DS weighed... 8lbs 8oz. I was astounded!

[Twinkletron]

My MW said I was having a 9lb baby...... He was 8lb 11.... And that was without a scan!!

[terilou87]

Interesting, iv been scanned every 4 week's since 28 weeks as have gd, last scan was at 36+5 and was estimated at 6lb1but his growth has slowed down, will be having a c section at 38+4 on Nye. Will be interesting to see how much he does weigh at that point. If scan is correct and from what I read weight gain is half a lb a week then he should be 7lb ish, ahh well I'll find out soon

[blueberryboybait]

Scanned at 39w as I was measuring big. Scan said she was 10lb 4 and would be about 10lb 10ish at 40 w. She was born at 39+6 weighing 6lb4. :)

[TransatlanticCityGirl]

Wow. Ok so all these stories confirm my suspicion.... while there are a good handful of accurate scans the overwhelming majority are way off. Will definitely be taking estimates with a grain of salt.

That said, my own gut is telling me this baby is going to be on the big side.. I'm betting on 10lbs or more. We'll find out in May.

NB: With DD midwife predicted based on my belly growth that she would be perfectly average at 7lbs 5 oz. She was only 2lbs 5oz off...

[TisTheSeasonToBeUnreasonable]

Ds1 scanned morning of delivery (36weeks) told he was 3lb 8oz - born 7hrs later at 6lb 11oz!

Ds2 scanned day before delivery (34weeks) told he was approx 3.5/4lbs - born at 5lb 2oz although he was dinky looked about 3.5/4lv even scbu team were surprised at his weight!

Dd1 scanned day 4says before delivery (35weeks) told 4lv approx and she was 5lb 4oz.

It's a subjective thing scanning, and lots if factors can throw the results off

[terilou87]

Just an update? So my 36+5 scan said 6lb 1 had ds yesterday at 38+4 weighing 6lb 13 so I would say quite accurate from my experience but also aware they can be notoriously inaccurate.