Optimal duration of exclusive breastfeeding

As a global health policy for both developing and developed countries, this review recommends exclusive breastfeeding for six months, followed by a combination of continued breastfeeding and safe, appropriate and adequate feeding with other foods.

RHL Commentary by Sguassero Y


In under-resourced settings, where sanitation and safe water are often lacking, breastfeeding can be life-saving. Breastfeeding protects against infectious diseases, especially gastrointestinal infections, which largely contribute to child morbidity and mortality in developing countries (1). However, if people believe that breast milk alone is nutritionally not sufficient for a baby beyond the age of three or four months, it may discourage health-care providers to recommend prolonged breastfeeding alone.

Two factors contributed to the revision of this review (2) in 2007. First, it has long been demonstrated that breastfed infants have different growth patterns compared with formula-fed infants (3). Secondly, recent research suggests that breastfeeding has positive long-term benefits, including possible protection against obesity (4, 5) and breast cancer (6). Keeping these factors in mind, the review authors sought and appraised the available scientific evidence on the optimal duration of exclusive breastfeeding. The primary objective of the review was to compare exclusive breastfeeding for 3–4 months versus exclusive breastfeeding for a full period of six month in terms of effects on the baby's health, growth and neuromotor or cognitive development as well as on maternal health.

The search methods for identifying relevant studies were comprehensive. Two independent searches were conducted in pertinent databases, including Latin American and Caribbean Literature, Index Medicus for the WHO Eastern Mediterranean Region and African Index Medicus. The literature search for updating the review was conducted in December 2006, with the addition of the LILACS, Sociofile, and EBM Reviews-Best Evidence databases. No language restrictions were applied.

The majority of the comparisons were based on one or two observational studies, predominantly cohort studies. Only two studies, conducted in an urban, low-income population in Honduras, were randomized controlled trials of exclusive breastfeeding versus mixed breastfeeding for 46 months. The latter involved just term babies weighing less than 2500 g at birth.

All the included studies had several methodological shortcomings.

The available data were insufficient to rule out an increase in the risk of growth failure in infants who were exclusively breastfed for six months. The pooled relative risks for undernutrition in terms of anthropometric z-scores <-2 at six months were 2.14 (0.746.24), 1.18 (0.562.50) and 1.38 (0.1710.98) for weight-for-age, for length-for-age and weight-for-length, respectively. However, these results should be considered with caution due to the small sample sizes.

The data were also insufficient to assess the risk of deficiency of micronutrients such as iron and zinc. A multicenter cluster randomized controlled trial conducted in maternity departments in Belarus found exclusive breastfeeding for 36 months to have a protective effect against gastrointestinal infection (7). This conclusion is strengthened by a meta-analysis bearing on this issue (8).

According to the review findings, exclusive breastfeeding for six months and continued breastfeeding with safe, appropriate and adequate feeding is recommended as a global health policy in both developing and developed countries. Nevertheless, one study from Honduras suggested that infants who are exclusively breastfed could have poor iron status. This piece of information should be particularly considered in under-resourced settings where perhaps most women are prone to be undernourished. More prolonged lactation amenorrhea was also highlighted in the review as an additional advantage of exclusive breastfeeding for mothers in developing countries.


2.1. Magnitude of the problem

Each year, new scientific and epidemiological evidence contributes to our knowledge about breastfeeding's role in the survival, growth, and development of children as well as about the health and well-being of mothers (8). Progress in exclusive breastfeeding rates has been made since the early 1990s, although the rates remain too low across the developing world and poor continuation of breastfeeding with inadequate complementary feeding practices is still widespread. Only about one-third (36%) of newborns are exclusively breastfed for the first six months of life. Current breastfeeding patterns are still far from the recommended level and considerable variation exists across regions. Based on data from 37 countries with trend data available (covering 60% of the developing world's population), the rate of exclusive breastfeeding for the first six months of life increased from 34% to 41% across the developing world between 1990 and 2004. Significant improvements were made in sub-Saharan Africa, where rates more than doubled from 15% to 32% during this same time period. Exclusive breastfeeding rates in South Asia and the Middle- East/North Africa also increased from 43% to 47% and from 30% to 38% between 1990 and 2004, respectively. Western and Central Africa, in particular, experienced significant improvements with rates rising from 4% to 22%, and Eastern and Southern Africa also showed improvements with exclusive breastfeeding rates increasing from 34% to 48%. Rates remained roughly constant in East Asia and the Pacific during this time (9).

It is also worth noting that each year undernutrition is implicated in about 40% of the 11 million deaths of children under five in developing countries, and lack of immediate and exclusive breastfeeding in infancy causes an additional 1.5 million of these deaths (10).

2.2. Applicability of the results

The review includes studies from various developing and developed country settings. The results could generally be regarded as applicable to under-resourced settings. The World Health Organization has released a new growth standard for young children based on research data collected from 8000 breastfed children from six different countries and this standard will also help in assessing the applicability in terms of growth patterns (11). The application of this new standard will encourage health-care providers to recommend exclusive breastfeeding and will reinforce health strategies for promoting prolonged breastfeeding.

Documentation of the evidence of the impact of breastfeeding on health outcomes is particularly important at this time, when concerns about transmission of HIV through breast milk are threatening programmes supporting continued breastfeeding. In the especially difficult circumstances faced by HIV-positive women, the benefits of breastfeeding must be weighed against the risk of mother-to-child transmission of HIV. Current policies continue support breastfeeding, especially exclusive breastfeeding, while ensuring informed choice on infant-feeding options. All HIV-infected mothers should receive counselling that includes general information about the risks and benefits of the various infant-feeding options and specific guidance in selecting the option most likely to suit their circumstances; they should also have access to follow-up care and support, including family planning and nutritional support (12).

Breastfeeding contributes to maternal health in the immediate postpartum period by helping the uterus to contract rapidly, thereby reducing blood loss. In the short term breastfeeding delays a woman's return to fertility (13), and in the long term it reduces the risk of cancers of the breast and ovary (5, 8). In many poor countries, feeding a child on breast milk eliminates expenditures on infant formula or other substitutes, which can be substantial.

2.3. Implementation of the intervention

Exclusive breastfeeding for the first six months of life is now considered a global public heath goal that is linked to reduction of infant morbidity and mortality, especially in the developing world. Mothers have the right to breastfeed their children, and breastfeeding is an essential component of measures that need to be taken to ensure that each child's right to food, health and care is respected. However, women are still striving to achieve maternity entitlements. There is a need to implement approaches that enable women to continue optimal feeding while and protect them from pressures to return to work early. These complex social and cultural pressures are often exacerbated by inaccurate medical advice from health-care workers who often lack proper skills and training in providing breastfeeding support.

From a national perspective, under Article 24 of the Convention on the Rights of the Child, governments and civil society should pursue full implementation of these human rights. Countries need to adopt protective maternity legislation to ensure that all hospitals and maternity facilities become centers of breastfeeding support for mothers. Similarly, for women in paid employment, minimum enabling conditions to prolong the duration of exclusive breastfeeding (such as paid maternity leave, part-time work arrangements, facilities for expressing and storing breast milk and breastfeeding breaks) are important measures to be considered.

Internationally, many large initiatives have been implemented during the last two decades to promote breastfeeding. UNICEF's strategy for infant and young child feeding has been based upon The Innocenti Declaration (10). The Declaration was adopted in August 1990 and was subsequently endorsed by the World Health Assembly and UNICEF's Executive Board for the protection, promotion and support of breastfeeding. Its four targets are:

  • implementation of comprehensive government policies on infant and young-child feeding;
  • full support from health and other sectors for two years of breastfeeding or more;
  • promotion of timely, adequate, safe and appropriate complementary feeding (addition of other foods while breastfeeding continues);
  • guidance on infant and young-child feeding, especially in difficult circumstances, and related support for families and caregivers; and
  • passing of legislation or taking suitable measures, to implement the International Code of Marketing of Breast-Milk Substitutes as part of the national comprehensive policy on infant and young-child feeding.

In May 2002, Member States of the United Nations reaffirmed the relevance and the urgency of the four Innocenti targets in the WHO/UNICEF Global Strategy for Infant and Young Child Feeding adopted by the World Health Assembly. The Global Strategy includes five additional operational targets:

  • appointment of a national breastfeeding coordinator with appropriate authority, and establishment of a multisectoral national breastfeeding committee;
  • implementation of 'Ten steps to successful breastfeeding' (i.e., the Baby-Friendly Hospital Initiative) in all maternity facilities;
  • global implementation of the International Code of Marketing of Breast-Milk Substitutes and subsequent relevant World Health Assembly resolutions in their entirety; and
  • enactment of imaginative legislation to protect the right of working women to breastfeed and establishment of means for enforcing legislation on maternity protection.

The World Breastfeeding Week (i.e. the first week of August each year) is important initiative of The Pan American Health Organization (WHO Regional Office for the Americas), Ministries of Health and nongovernmental organizations such as La Leche League (14) aimed at promoting and supporting breastfeeding. During this week, conferences, parades, art shows, and special events are organized especially for mothers and their infants.

3. Research

Published studies of the effects of breastfeeding on child and maternal health have several methodological flaws. Use of a standard definition of breastfeeding, controlling for a variety of potentially confounding variables, and making efforts to control for reverse causality by excluding deaths near birth could make future studies more reliable.

For outcomes for which data are currently lacking, well-conducted randomized controlled trials are needed, except for 'infant mortality' because it would be very difficult to design ethically acceptable studies that include infant mortality as an outcome.


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This document should be cited as: Sguassero Y. Optimal duration of exclusive breastfeeding: RHL commentary (last revised: 28 March 2008). The WHO Reproductive Health Library; Geneva: World Health Organization.

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