Using NHS data for scientific research – without creating a privacy nightmare(takes.jamesomalley.co.uk)

  Knowing the approximate date range in which someone had a medical intervention, their 
  approximate age, and their approximate location is often enough to re-identify someone in a 
  pseudonymised dataset, and then – illegally – to see everything else in their record. Women 
  face particular concerns: knowing someone’s approximate age, approximate location, and the 
  approximate time at which they had children can also often be enough to make a confident 
  unique match; this is the kind of information that will be known by someone at the school 
  gate, or a colleague. This is not to say that health data users are untrustworthy: but the 
  system must be resilient to untrustworthy users; and it is well documented that other large 
  administrative national datasets are sometimes misused.[1]