This study compares data on the prevalence and duration of breastfeeding in Switzerland between 2003 and 1994, and identifies potential risk factors and the effect of the "Baby Friendly Hospital Initiative." In addition, the introduction of complementary feeding and Vitamin D supplementation are investigated. During the summer of 2003 a questionnaire was sent to a random sample of mothers who had given birth during the previous nine months. The questionnaire included questions about birth, the health of the mother and child, socio-economic status, a 24 hour dietary recall, and detailed questions on breastfeeding as well as the first introduction of different foods and drinks. The results of this study were published in the 5th Swiss Nutrition Report.