| Excerpt from The WHO Reproductive Health Library | Published by Update Software Ltd. |
This review was commissioned by the World Health Organization in an effort to resolve the longstanding debate on the optimal duration of exclusive breastfeeding (EBF). Its primary objective was to compare the benefits for the health, growth and development of the child and for maternal health outcomes of EBF for 4–6 months with EBF for a full period of 6 months. The authors' task was complex, owing largely to the paucity of suitable studies. The review was based on two small randomized controlled trials and 17 observational studies that varied in quality. As a result, most comparisons were based on 1 or 2 studies only. There was also significant heterogeneity for some of the comparisons, especially those from observational studies.
The evidence does not suggest an adverse effect of EBF for 6 months on infant growth on a population basis, that is, on average. However, sample sizes were not large enough to rule out an increased risk of growth faltering in some infants who are exclusively breastfed for 6 months (e.g. the pooled relative risk from the two trials for weight-for-age Z-scores <-2 at 6 months was 2.14 (0.74-6.24)). The data were also limited with respect to iron status of children. However, the data pointed to a poorer iron status in infants who received EBF for 6 months. This evidence is likely to apply especially to populations in which maternal iron status and infant endogenous stores are not optimal. The data were insufficient to assess the risks of deficiencies of other micronutrients, and it was not possible to draw any inferences concerning developmental outcomes. In developing-country settings, one of the most important potential advantages of EBF for 6 months is the reduction of mortality from infectious diseases, especially diarrhoeal diseases. Unfortunately, no mortality data were available that directly compared EBF for 4-6 months versus 6 months. A cluster randomized trial conducted in maternity departments in Belarussia found EBF for 6 months to have protective effects against gastrointestinal infection, but no other significant reduction in infectious morbidity or atopic disease was demonstrated.
On the basis of this review, EBF for 6 months can be recommended as a global public health recommendation for all populations. However, individual infants must still be managed on a case-by-case basis in order to ensure that if growth falters or if there are other adverse effects, these are not ignored and appropriate measures are taken.
The search strategy was comprehensive and far-reaching. In order to capture all relevant studies, two independent searches covering numerous databases were conducted: one by staff at the Department of Nutrition of WHO and the other by the authors themselves. For both searches, every effort was made to identify relevant English and non-English language articles. Because few studies strictly adhered to the WHO definition of EBF, the term was used to include both exclusive and predominant breastfeeding. The method of stratifying the studies according to study design (randomized controlled trial versus observational study) and provenance (developing versus developed country) was appropriate.
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