The prevalence of breastfeeding varies very much throughout the world. In some countries, such as in Scandinavia, it is extremely high, whereas it is rather low in many industrialized countries such as northern Italy. In urban areas of many developing countries the prevalence is extremely low, although it may be high in rural areas. For instance, in rural Guinea-Bissau in West Africa it is reported to be 100% at 3 mo of age, and this high prevalence may be explained by the fact that infants who have not been breastfed die before this age. In Sweden the prevalence at 2 mo of age was around 95% in 1945 (including infants fed by milk-mothers) but then gradually dropped until 1972, when it was as low as 20%. However, during the following 10-y period the prevalence gradually increased to around 80%. The main reasons for the decline most probably were that infant formulae, then considered to be safe, became available, that an increasing number of women started to work outside their homes, making formula feeding part of the feminist movement, and finally that no real attempts were made to promote breastfeeding in the maternity wards and well-baby clinics. The reverse trend started in 1972, when the attitude towards breastfeeding changed completely. Well-educated mothers became aware of the new discoveries of the importance of breastfeeding from immunological and nutritional points of view, and organized campaigns. Within a few years, the Swedish parliament passed a law which guaranteed all mothers paid leave from their work (80% of their salary) for 9 mo after childbirth, which has now been increased to 12 mo. The WHO/UNICEF code from 1980, which regulates the marketing of infant formula, has also probably played an important role. After a plateau for the prevalence of breastfeeding between 1982 and 1990, a further increase has taken place, particularly between 6 and 9 mo of age. Whereas the first phase in the increase of the prevalence of breastfeeding was, to a certain extent, the result of the concern of well-educated mothers, the second phase (1990-1998) may, at least partly, be explained by the fact that Swedish maternity wards then implemented the suggestion, launched by WHO/UNICEF, to create "baby-friendly" maternity hospitals with the aim of enabling all women to practise exclusive breastfeeding immediately after birth. Methods to stimulate lactation and proper nutritional suckling behaviour of the newborn were then developed.