well personally I had my dd aged 29, oddly the same as my Mum and my Gran (although that wasn't my mum's mum! who had her last at 42! and she had 8!! notibly all boys bar my mum, the last!)
I have to say this was the right age for me, as I certainly wasn't sorted enough in myself to deal with anyone bar myself up until then (men included, but that probably reflected in my choice of them upuntil then also...), a selfish comment, but a true one. Glad I waited as I am enjoying being a mum now, and certainly would not have wanted to be one any earlier.
I have always wholeheartedly respected anyone who is a mum, as many of my friends did the journey way before I, as its bloody hard work, no matter what age you are!