Abstract
This review has been amended to include further information on Menigaux 2000 pre pre and Menigaux 2000 post included studies. At July 2014, this review is out of date and has been withdrawn. This review is correct as of the date of publication. The latest version is available in the ‘Other versions’ tab on The Cochrane Library, and may still be useful to readers. The editorial group responsible for this previously published document have withdrawn it from publication.