The search sought to find both published and unpublished studies in the English language. Databases were searched up to and including August 2002 and included MEDLINE, CINAHL, Current Contents, Cochrane Library, Expanded Academic Index, Electronic Collections Online, Turning Research Into Practice (TRIP), The Australian Breast-feeding Association Lactation Resource Centre, Dissertation Abstracts and Proceedings First. The reference lists of all identified studies were searched for additional studies.