Definitely do one. As PP say, it's good to get your wishes down on paper. I think it's presumptuous of the midwife to assume that your birth plan would only include 'routine' things - there are many preferences when labouring and giving birth that can differ from person to person. And it can be hard to remember, let alone communicate these, in the throes of labour. I know DH found it useful to refer to. Assuming that all her 'patients' want exactly the same thing is like going clothes shopping and all the clothes are the same!