example, young women with long term conditions may find that they need to plan carefully for pregnancy and make sure that their midwives understand their circumstances. There are many aspects of people's lives, values and preferences that doctors cannot be expected to know about. These include how people balance length of life and quality of life, avoidance of specific effects of medicines, their views of invasive interventions and their moral views Patients whose preferences were acknowledged often felt that this had contributed to an appropriate treatment decision. It is sometimes surprising to doctors that people who get involved in treatment decisions often opt for less, rather than more, medical intervention. For example, Di was appalled at the suggestion she should have a mastectomy to treat DCIS, (precancerous cells in her breast). (See ' Why do people sometimes not want a decision to be shared ?' ). There are of course many counter examples of people who are told that no intervention is possible and then find out about a new treatment, or discover an experimental treatment trial and ask if they can take part. People with a family history of cancer may choose to have preventative surgery. Parents of children with autism sometimes struggle to get a diagnosis for their child -- not because they have any major expectations of treatment but because they know that their child will be helped at school once they have a diagnosis. As we discuss elsewhere on this site (see ' What is shared