WHO recommends mothers worldwide to exclusively breastfeed infants for the child's first six months to achieve optimal growth, development and health. Thereafter, they should be given nutritious complementary foods and continue breastfeeding up to the age of two years or beyond.
The latest systematic review of the evidence on this issue was published in 2009 ("Optimal duration of exclusive breastfeeding (Review)", Kramer MS, Kakuma R. The Cochrane Library, 2009, Issue 4). The findings of the review, which included two controlled trials and 18 other studies conducted in both developed and developing countries, support current WHO recommendations.
The systematic review's findings suggest that exclusive breastfeeding of infants with only breast milk, and no other foods or liquids, for six months has several advantages over exclusive breastfeeding for 3-4 months followed by mixed breastfeeding.
These advantages include a lower risk of gastrointestinal infection for the baby, more rapid maternal weight loss after birth, and delayed return of menstrual periods. No reduced risks of other infections or of allergic diseases have been demonstrated. No adverse effects on growth have been documented with exclusive breastfeeding for six months. But a reduced level of iron has been observed in some developing country settings.
WHO closely follows new research findings and has a process for periodically re-examining recommendations. Systematic reviews accompanied by an assessment of the quality of evidence are used to review guidelines in a process that is designed to ensure that the recommendations are based on the best available evidence and free from conflicts of interest.