Ah don't you love silly answers such as Mark's!
Ok, so I am a writer, and I live in this really beautiful town, full of trees, ferns, rivers; it's gorgeous. And the town next to mine is called : Kallista. I'm naming one of the characters in my story Callista, as they are pronounced the same but with different spelling. It's pronounced: Kah-list-ah. (kah as in car but without the r) (List as in shopping list) (ah as in a sigh).
Whether you spell the name 'Kallista', 'Callista', or 'Calista', the name is a gorgeous one, and ironically enough means 'beautiful'. Also, I don't know how far into your pregnancy you are, but if it's not far there IS a chance of you having twins. If this is the case I would recommend the name 'Arabella' for the second child (if they're girls) because that also means 'beautiful', and I think it'd be sweet to have two kids with the same name meaning.
Okay, well, I hope this isn't an information overload. I hope that this helps you, and I hope that your child is everything you dream she/he will be. :) Good luck, and I hope you find the perfect name!
~P.s, I'm Australian, so my accent might change the pronunciation, but all the tourists who come by seem to pronounce it the same way as I do. ~
An Australian Writer - Me! :)