Growth of breast-fed infants deviates from current reference data: a pooled analysis of US, Canadian, and European data sets. World Health Organization Working Group on Infant Growth.

OBJECTIVE: To compare growth patterns of a large sample of breast-fed infants with the current World Health Organization (WHO)/Centers for Disease Control and Prevention (CDC) reference data. METHODS: Data from seven longitudinal studies of infant growth in North America and northern Europe were pooled (n = 453 breast-fed infants). Weight, length and head circumference were compared with the WHO/CDC reference, and repeated-measures analysis of variance was used to examine associations between growth patterns and breast-feeding duration, age of introduction of solid foods, and use of other milks. RESULTS: In comparison with WHO/CDC reference data, infants breast-fed for at least 12 months (n = 226) grew more rapidly in the first 2 months and less rapidly (particularly in weight) from 3 to 12 months; the mean z score at 12 months was -0.53 for weight for age, -0.29 for length for age, and -0.32 for weight for length. In contrast, mean head circumference was well above the WHO/CDC median throughout the first year of life. These patterns were generally consistent across studies. In the full sample (n = 453), a longer duration of breast-feeding was associated with a greater decline in weight for age and weight for length but not length for age. CONCLUSION: These results suggest that if growth charts are to reflect patterns consistent with those of infants following WHO feeding recommendations, new reference data based on breast-fed infants are needed.