Bra - what 'size' should dd start wearing one?

[SpringSunshine]

Title says it all really - should they start wearing a bra from first 'buds' or wait as long as possible to let the muscles strengthen?

Passthetwiglets I know!

I was mortified for her, but at the time it seemed easier just to say " daft woman doesn't really realise that your age doesn't determine your bra size", and wandered to bravissimo again.