Estimated birth weight - how accurate?

[Jcmummy32]

Hi everyone

I had a scan today at 31wks pregnant and his tummy is measuring in 92 percentile/weighting 4lbs1oz. I’m worried this means I’ll have a baby that’s way bigger. What were your experiences with predicted birth weight and actual birth weight?

Had a growth scan at 38 weeks and baby was 'already' 7lbs and change. She was born at 40 + 5 weighing 6 lb 13. So either she lost weight (and didn't gain the 0.5 lb a week she was meant to, or the scan was wrong... I'm going with the scan being off by at least a lb.

With DS I had growth scans at 28 and 32 weeks. His estimated weight at 32 weeks was 4lbs 11oz which I think was around the 70th centile. He was 8lbs 15oz when born at 41 weeks which I think was fairly consistent with his estimated centile. I seem to remember that he had a slightly larger AC too but GDM tests were all negative so no one was worried.

I had growth scans at 34 and 37 weeks with DD. Her growth chart suggested she’d be about 7lbs 10oz at 40w based on those scans. She was 8lbs 1oz so fairly close (and to be fair both the midwife and I felt she’d had a little growth spurt in the last week or two).

I was told to buy tiny baby clothes as he wouldn't be more than 5/6lb. He was 8lb!

I was told on the Friday at 38 weeks that it was a huge baby, well over 9lb already.
Baby was born the next day at 8lb 4 oz.

I had "growth scans" (tape measure) that put my baby at 7.5lbs and a private scan at 36 weeks that estimated the same and they were spot on. My sister on the other hand was induced because of their suspicions baby was already 9lb, she was 6.5. Sometimes it's accurate, other times not so much.

I was told he was going to be about 6 lb,he was born at 8 lb 12.

Out by about 1lb. So based on previous babies I expected DS to be bigger. But growth scans weren't routine with my eldest 3.

DS was estimated to be just under 9lb at 37wks. He was born at 40wks (induced) weighing 9lb5. Therefore he was likely closer to 8lb (which is still a ridiculous size for a 37wker) when I was scanned.

Had he not been induced and gone to 42wk like his sisters he would have been about 10lb5. But he had positional talipes from being squashed so maybe he would have come sooner 🤷‍♀️

DS was estimated to be 7lb in a scan at 38 weeks. He was born at T+3 weighing 8lb 7oz, so as they reckon baby puts on about 1/2lb a week close to due date, it was pretty accurate.

Accurate for me. On DD1 I had a scan the day I was inducted which estimated 10lb, she was 9lb 7oz.

I had scans at 34 and 36 weeks on DD2, I can't remember the weights but they were high (maybe 6lb 9oz at 34 weeks). She was 9lb 12oz when born at 39 weeks which was in the right ballpark.

These threads always get loads of replies from people whose scans were off, but I suspect there's a large silent majority for whom they were a pretty good estimate.

Mw said dd would be 3.2 kgs or 3.3. She was 4.2.

I had a scan last week 31 weeks pregnant and baby is 5lb 9oz stomach and head measurements are way of chart above 99th centile .
My last two babys were small but I’ve been type 2 diabetic for the last 4 year .
I’m worrying about it and I have another scan in two weeks . 🥲
I’m having a planned section but I keep worrying about how big he is going to be . This is my first boy my girls were 6lb 2 and 7lb 3

I had a scan at 32 weeks and was told baby is 'particularly big'. They didnt tell me what weight she was expected to be. I was freaked thinking I was having a massive baby and I am 5 foot nothing. I had my baby last week at 40+3 and she weighed 7lbs 15oz. DD1 was 7lbs 13oz at 39+6, so clearly DD2 was smaller than DD1 would have been.

My advice is dont always trust the accuracy of the scans. Babies grow at different rates, and many I have spoken to have said, especially over the past year or so, that they have been told their babies are big when they turned out to be a pretty average weight at birth.

Dc1 was predicted to be 7lb8oz was over 9lb.
Dt were predicted to be 5lb each 3 days before birth (they were actually both over 6lb) so in my case all really inaccurate.

Thanks so much everyone. I really struggle with anxiety so every response helps. This might sound silly but does a big baby mean I’m potentially further on that I thought/due date is wrong? Or am I overthinking it? Sorry, I just get really anxious x

Pretty accurate for me. 36 week scan estimated DD to be 6lb 15oz. DD arrived a week later weighing 7lb 5oz.

The scan might have occurred just after a growth spurt. Is there any history of big babies in your family? Are you or your partner tall? Do you have gestational diabetes? There's lots of factors that can cause a baby to be big.

Accurate for me, measuring low birth weight of 4lb9oz at 36.2 days and at 37 weeks she was born weighing 4lb13oz.

First baby 5lb 12 oz at 36 weeks estimated 7lb 12 oz on due date born 40 + 3 at 8lb 3oz so fairly accurate.

Number 2 estimated 4lb 2 oz at 32 weeks
6lb 10 oz at 36 weeks estimated around 8lb 4 on due date was born 37 + 4 weighing 8lb 3 oz.

Number three estimated 6lb 12oz at 36 weeks, estimated 8lb 5oz oz due date and born at 37 weeks exactly weighing 8lb 3oz so babies 2 and three were underestimated.

Ds measured above the 95th percentile at 36 weeks, he was born at 39+4 9lb 2oz. Though I don't agree with the due date I was given, they put me back 10 days from the date I calculated from LMP. Dd was estimated to be 5lb 8oz at 35w, she was born on her due date 7lb 10oz.

Scan at 28 weeks suggested 7lb 7, my growth chart suggested 8lb 8. He was born at 41+4 on Friday night and was actually 9lb 15 so I don't think much of these estimates at all now.