Fundal height accuracy

[GYMBALL]

How accurate are fundal height measurements ?
I'm 30 weeks but measuring 35 . This is my 5th pregnancy and my last two babies were over 10lb so not exactly tiny . I also have diastisis recti and I'm overweight . Can this affect fundal measurement ? Or does it mean my dates are out ? I had an early ultrasound at 6 weeks as well as the 12 week one so I'm not sure how my dates could be wrong .
I had a growth scan at 28 weeks and baby is on 90th centile

I don't really think they are that accurate. I was told all the way through with my third he was on the 90% line I had scans and measurements. They ended up delivering him a week early at 7lb. Hardly the biggest of babies taking into account my first born was 9lb1oz

The measurements are nearly useless especially if you’re overweight. And it bears no relevance to your due date - this is set by your 12 weeks scan and not by how big your tummy gets.

Fundal height is subjective. Most accurate when performed by same midwife/ doctor throughout.

Load of rubbish - totally inaccurate for us!

I know they're very helpful for picking up "small for dates" babies but don't know to what extent they're affected by being overweight.

At my 28 week apt last month I was measuring 6 weeks ahead! It's my second baby, am not overweight or have any issues had urgent scan baby was measuring bang on maybe a week or so ahead but water levels all normal and everything so I think a midwife with a measuring tape is really not very accurate at all so I wouldn't worry at all.