http://www.ajcn.org/cgi/content/abstract/78/2/291

American Journal of Clinical Nutrition, Vol. 78, No. 2, 291-295, August 2003
© 2003 American Society for Clinical Nutrition
 

Infant growth and health outcomes associated with 3 compared with 6 mo of exclusive breastfeeding^1,2,3

Michael S Kramer, Tong Guo, Robert W Platt, Zinaida Sevkovskaya, Irina Dzikovich, Jean-Paul Collet, Stanley Shapiro, Beverley Chalmers, Ellen Hodnett, Irina Vanilovich, Irina Mezen, Thierry Ducruet, George Shishko and Natalia Bogdanovich

¹ From the Departments of Pediatrics (MSK, RWP, and J-PC) and Epidemiology and Biostatistics (MSK, TG, RWP, J-PC, SS, and TD), McGill University Faculty of Medicine, Montreal; the Centre for Research in Women’s Health (BC), Sunnybrook Women’s College Health Sciences Centre (BC), and Faculty of Nursing (EH), University of Toronto; the Departments of Maternal and Child Health (ZS) and Foreign Relations (IM), Belarussian Ministry of Health, Minsk, Belarus; and the Belarussian Maternal and Child Health Research Institute (ID, IV, GS, and NB), Minsk, Belarus.

Background: Opinions and recommendations about the optimal duration of exclusive breastfeeding have been strongly divided, but few published studies have provided direct evidence on the relative risks and benefits of different breastfeeding durations in recipient infants.

Objective: We examined the effects on infant growth and health of 3 compared with 6 mo of exclusive breastfeeding.

Design: We conducted an observational cohort study nested within a large randomized trial in Belarus by comparing 2862 infants exclusively breastfed for 3 mo (with continued mixed breastfeeding through 6 mo) with 621 infants who were exclusively breastfed for 6 mo. Regression to the mean, within-cluster correlation, and cluster- and individual-level confounding variables were accounted for by using multilevel regression analyses.

Results: From 3 to 6 mo, weight gain was slightly greater in the 3-mo group [difference: 29 g/mo (95% CI: 13, 45 g/mo)], as was length gain [difference: 1.1 mm (0.5, 1.6 mm)], but the 6-mo group had a faster length gain from 9 to 12 mo [difference: 0.9 mm/mo (0.3, 1.5 mm/mo)] and a larger head circumference at 12 mo [difference: 0.19 cm (0.07, 0.31 cm)]. A significant reduction in the incidence density of gastrointestinal infection was observed during the period from 3 to 6 mo in the 6-mo group [adjusted incidence density ratio: 0.35 (0.13, 0.96)], but no significant differences in risk of respiratory infectious outcomes or atopic eczema were apparent.

Conclusions: Exclusive breastfeeding for 6 mo is associated with a lower risk of gastrointestinal infection and no demonstrable adverse health effects in the first year of life.

Key Words: Breastfeeding • gastrointestinal infection • respiratory infection • growth • atopic eczema

Copyright © 2003 by The American Society for Clinical Nutrition, Inc.