The Optimal Duration of Exclusive Breastfeeding
Although the health benefits of breastfeeding are acknowledged widely, opinions and recommendations are divided on the optimal duration of exclusive breastfeeding. We systematically reviewed available evidence concerning the effects on child health, growth, and development and on maternal health of exclusive breastfeeding for 6 months vs. exclusive breastfeeding for 3–4 months followed by mixed breastfeeding (introduction of complementary liquid or solid foods with continued breastfeeding) to 6 months. Two independent literature searches were conducted, together comprising the following databases: MEDLINE (as of 1966), Index Medicus (prior to 1966), CINAHL, HealthSTAR, BIOSIS, CAB Abstracts, EMBASE-Medicine, EMBASE-Psychology, Econlit, Index Medicus for the WHO Eastern Mediterranean Region, African Index Medicus, Lilacs (Latin American and Carribean literature), EBM Reviews-Best Evidence, the Cochrane Database of Systematic Reviews, and the Cochrane Controlled Trials Register. No language restrictions were imposed. The two searches yielded a total of 2,668 unique citations. Contacts with experts in the field yielded additional published and unpublished studies. Studies were stratified according to study design (controlled trials vs. observational studies) and provenance (developing vs. developed countries).
The main outcome measures were weight and length gain, weight-for-age and length-for-age z-scores, head circumference, iron status, gastrointestinal and respiratory infectious morbidity, atopic eczema, asthma, neuromotor development, duration of lactational amenorrhea, and maternal postpartum weight loss.
Twenty independent studies meeting the selection criteria were identified by the literature search: 9 from developing countries (2 of which were controlled trials in Honduras) and 11 from developed countries (all observational studies). Neither the trials nor the observational studies suggest that infants who continue to be exclusively breastfed for 6 months show deficits in weight or length gain, although larger sample sizes would be required to rule out modest increases in the risk of undernutrition. The data are conflicting with respect to iron status but suggest that, at least in developing-country settings, where iron stores of newborn infants may be suboptimal, exclusive breastfeeding without iron supplementation through 6 months of age may compromise hematologic status. Based primarily on an observational analysis of a large randomized trial in Belarus, infants who continue exclusive breastfeeding for 6 months or more appear to have a significantly reduced risk of one or more episodes of gastrointestinal tract infection. No significant reduction in risk of atopic eczema, asthma, or other atopic outcomes has been demonstrated in studies from Finland, Australia, and Belarus. Data from the two Honduran trials suggest that exclusive breastfeeding through 6 months of age is associated with delayed resumption of menses and more rapid postpartum weight loss in the mother.
Infants who are breastfed exclusively for 6 months experience less morbidity from gastrointestinal tract infection than infants who were mixed breastfed as of 3 or 4 months of age. No deficits have been demonstrated in growth among infants from either developing or developed countries who are exclusively breastfed for 6 months or longer. Moreover, the mothers of such infants have more prolonged lactational amenorrhea and faster postpartum weight loss. Based on the results of this review, the World Health Assembly adopted a resolution to recommend exclusive breastfeeding for 6 months to its member countries. Large randomized trials are recommended in both developed and developing countries to ensure that exclusive breastfeeding for 6 months does not increase the risk of undernutrition (growth faltering), to confirm the health benefits reported thus far, and to investigate other potential effects on health and development, especially over the long term.
Unable to display preview. Download preview PDF.
- [AAP] American Academy of Pediatrics, Committee on Nutrition. Pediatric Nutrition Handbook. 4th Edition. Elk Grove Village, Illinois: American Academy of Pediatrics, 1998.Google Scholar
- Brown K. The relationship between diarrhoeal prevalence and growth of poor infants varies with their age and usual energy intake. FASEB J 1991;5:A1079.Google Scholar
- Brown K, Dewey K, Allen L. Complementary Feeding of Young Children in Developing Countries: A Review of Current Scientific Knowledge. Geneva: WHO, 1998.Google Scholar
- Butte N. Energy requirements of infants. Eur J Clin Nutr 1996;50(Suppl):24–36.Google Scholar
- Castillo C, Atalah E, Riumallo J, Castro R. Breast-feeding and the nutritional status of nursing children in Chile. Bull PAHO 1996;30:125–133.Google Scholar
- Dewey K, Peerson J, Brown K, Krebs N, Michaelsen K, Persson L, Salmenpera L, Whitehead RG, Yeung DL. Growth of breast-fed infants deviates from current reference data: a pooled analysis of US, Canadian, and European data sets. Pediatrics 1995b;96:495–503.Google Scholar
- Dewey K, Cohen R, Rivera L, Brown K. Effects of age of introduction of complementary foods on micronutrient status of term, low-birthweight, breastfed infants in Honduras. FASEB J 1998a;12:A648.Google Scholar
- Dewey K, Cohen R, Rivera L, Brown K. Effects of age introduction of complementary foods on iron status of breast-fed infants in Honduras. Am J Clin Nutr 1998b;67:878–884.Google Scholar
- [FAO/WHO] Food and Agriculture Organization of the United Nations/World Health Organization. Energy and protein requirements. 52: FAO Nutrition meetings. Rome: FAO, 1973.Google Scholar
- Frongillo EJ, de Onis M, Garza C. The World Health Organization Task Force on Methods for the Natural Regulation of Fertility. Effects of timing of complementary foods on post-natal growth. FASEB J 1997;11:A574.Google Scholar
- Kramer MS, Chalmers B, Hodnett ED. Breastfeeding and infant growth: biology or bias? Pediatr Res 2000a;47:151A.Google Scholar
- Kramer MS, Chalmers B, Hodnett ED, Sevkovskaya Z, Dzikovich I, Shapiro S, Collet JP, Vanilovich I, Mezen I, Ducruet T, Shishko G, Zubovich V, Mknuik D, Gluchanina E, Dombrovsky V, Ustinovitch A, Ko T, Bogdanovich N, Ovchinikova L, Helsing E. Promotion of breastfeeding intervention trial (PROBIT): A cluster-randomized trial in the Republic of Belarus. In: Koletzko B, Michaelsen KF, Hemell O, editors. Short and Long Term Effects of Breast Feeding on Child Health. New York: Kluwer Academic/Plenum Publishers, 2000b: 327–345.Google Scholar
- Kramer MS, Chalmers B, Hodnett ED, Sevkovskaya Z, Dzikovich I, Shapiro S, Collet JP, Vanilovich I, Mezen I, Ducruet T, Shishko G, Zubovich V, Mknuik D, Gluchanina E, Dombrovskiy V, Ustinovitch A, Kot T, Bogdanovich N, Ovchinikova L, Helsing E; PROBIT Study Group. Promotion of breastfeeding intervention trial (PROBIT): A randomized trial in the Republic of Belarus. JAMA 2001;285:413–420.CrossRefPubMedGoogle Scholar
- [UNICEF] United Nations Children’s Fund. Facts for Life. Wallingford: P&LA, 1993.Google Scholar
- Whitehead R, Paul A. Infant growth and human milk requirements. Lancet 1981;161–163.Google Scholar
- [WHO] World Health Organization. Indicators for Assessing Breast-Feeding Practices. Geneva: WHODocument WHO/CDD/SER 1991;91:14.Google Scholar
- [WHO] World Health Organization. Working Group on Infant Growth. An evaluation of infant growth. Geneva: WHO, 1994.Google Scholar
- [WHO] World Health Organization. Information and attitudes among health personnel about early feeding practices. WHO Wkly Epidemiol 1995a;l 17–120.Google Scholar
- [WHO] World Health Organization. Working Group on Infant Growth. An evaluation of infant growth: the use and interpretation of anthropometry in infants. Bull WHO 1995b;73:165–174.Google Scholar
- [WHO]World Health Organization. Collaborative Study Team on the Role of Breastfeeding on the Prevention of Infant Mortality. Effect of breastfeeding on infant and child mortality due to infectious diseases in less developed countries: a pooled analysis. Lancet 200la;355:451–455.Google Scholar
- [WHO] World Health Organization. Infant and young child nutrition. Fifty-fourth World Health Assembly. Geneva: WHO 54.2;2001bGoogle Scholar
- [WHO] World Health Organization. Working Group on the Growth Reference Protocol and WHO Task Force on Methods for the Natural Regulation of Fertility. Growth of healthy infants and the timing, type, and frequency of complementary foods. Am J Clin Nutr 2002;76:620–627.Google Scholar