Don't know if this is any use as part of a supporting reference, using Sackett 1996 and their concept of the evidence triad or maybe evidence based triad, where evidence based practice originally comprised of recent evidence, the woman's values and expectations and the practitioner's skills. You can find the reference for this from Soo Downe's book Normal Childbirth and Denis Walsh's book too, in fact you can google Sacket 1996 the evidence based triad.

I suppose with finding out what is important to the woman, you need to consider any cultural or religious expectations, her previous experience of the third stage and in an indirect way, what her vision of how her labour and birth will be.

Clear as mud, eh?