Recommendation WHO

For the WHO European Region, it is recommended that all infants should be exclusively breastfed from birth to about 6 months of age, and at least for the first 4 months of life. Some infants may need complementary foods before 6 months of age, but these should not be introduced before 4 months. Signs that complementary foods should be introduced before 6 months are that the baby, in the absence of obvious disease, is not gaining weight adequately (based on two or three sequential assessments) (see Chapter 10), or appears hungry after unrestricted breastfeeding. Attention should be paid to the use of appropriate growth reference charts, bearing in mind that breastfed infants have growth rates that differ from those on which the US National Center for Health Statistics references are based (12). Nevertheless, consideration should also be given to other factors, including birth weight and the gestational age, clinical condition and overall growth and nutritional status of the infant when starting complementary feeding before 6 months. A study in Honduras (13) found that the provision of free, high-quality complementary foods from the age of 4 months to breastfed infants with a birth weight between 1500 g and 2500 g did not confer a growth advantage. These findings support the recommendation for exclusive breastfeeding for about 6 months, even in low-birth-weight infants.

Feeding and nutrition of infants and young children : Guidelines for the WHO European Region, with emphasis on the former Soviet countries, World Health Organisation, 2003
http://www.euro.who.int/document/WS_115_2000FE.pdf