# What are the -SD lines on growth charts??



## divadexie

What does the -SD stand for?

And why is it in low birth weight growth charts?

I have never heard this term used before :/

But if it will get my HV off my back I want to know what it is! 

Lol and why it is used what does it mean?

She is just on the 4th centile and my HV now wants to start coming to waigh weekly again! Aaah I hate the woman.


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## Marleysgirl

It stands for Standard Deviation, and it's something to do with normalised graphs. I did study stats a couple of years ago but never did get my head around these! The -ve SD (percentile) growth lines fall below the 0.4th percentile growth line. 

Not sure that'll help keep your HV off your back, I'd imagine she's coming because Anna isn't maintaining her growth and is falling down through the percentiles. Whereas Andrew maintains his growth, albeit well down the graph on the -3 SD growth line, our problem is that they would have expected him to start climbing up the graph (ie catching up in weight) and he's not.


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## Fiestagal

So that's what it stands for! I did wonder. Connor is very much like Andrew. We have been told that they would expect him to start climbing the centiles now but he isn't, he is maintaining his own curve too though. He did slow down a little when teething and is about 15lb at the moment, he is nearly 15 months.


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## Marleysgirl

Longer explanation in the other thread :D And I've still managed to avoid trying to explain how you draw a normal distribution graph for weights at a specified age, the mean then being the 50th (per)centile, how the curve tails off at both ends, how the standard deviation can be calculated ......... Anyone asleep yet?


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