Talk to new parents and you'll find them boasting or puzzling over how their infants measure up to the pediatrician's growth chart. However, an extensive, international study led by nutritionists at the University of California, Davis, suggests that the growth rate of breast-fed babies differs significantly from that of formula- fed babies and that growth charts should be revised to reflect that difference. Findings of the study will be published in the September issue of Pediatrics, the journal of the American Academy of Pediatrics. "One of the most striking differences revealed by this study is that healthy, breast-fed babies tend to grow more rapidly than predicted by growth charts during the first two to three months; then their rate of growth slows compared to that of formula-fed infants," said Kathryn G. Dewey, a UC Davis nutrition professor. "This is important, because if the child's growth appears to be faltering in comparison to the growth chart, the nursing mother may be counseled -- perhaps inappropriately -- that her breast milk production is inadequate and that formula or other complementary foods should be added to the child's diet." Discontinuation of breast-feeding is of particular concern for babies between the ages of 3 and 6 months in developing countries especially, where baby formula is expensive and alternative foods may not be sanitary. "This study indicates that if infant growth charts are to reflect patterns consistent with World Health Organization recommendations for breast-feeding, new data based on the growth of breast-fed infants are needed," said Dewey. The World Health Organization suggests that babies receive only breast milk for at least the first four to six months of life, to provide optimum nutrition and protection from infection, she said. Dewey and colleagues combined the results of their own research at UC Davis with data from six different studies conducted in North America and northern Europe, looking at the length, weight and head circumference of 453 infants who were breast-fed for at least four months. Researchers also examined growth patterns associated with the duration of breast-feeding, age of introducing solid foods and the supplementary use of formula or other milks. These measurements were compared with figures in the growth charts used by both the World Health Organization and the U.S. National Center for Health Statistics. The study was conducted under the auspices of the World Health Organization, which is preparing to revise its infant growth charts. "The data on which the current national and international growth charts are based are inadequate for assessing growth of breast-fed infants, because the measurements were taken infrequently and because the sample group included few babies who were breast-fed for an entire year," said Dewey. In the United States, she noted, less than 10 percent of all infants are breast-fed for 12 months. An authority on maternal and child nutrition, Dewey has been studying the growth and nutritional status of breast-fed and formula-fed infants for more than a decade. This most recent study was funded by Wellstart International through the U.S. Agency for International Development.