New parents breathe a sigh of relief when the doctor pronounces at periodic checkups that their infant's weight and length are near the 50th percentile, indicating that the child is growing at the average expected rate. Last fall, the Journal of Pediatrics published tables of reference for 2-month and 3-month weight and length increments, which the authors recommended as an aid to detect growth faltering. But a study by nutritionists at UC Davis suggests that the method used to establish these benchmarks of growth may be flawed, because it uses estimated increments generated from a mathematical model rather than actual increments. Since this causes bias in the lower percentiles, both formula-fed and breast-fed infants may be improperly classified as poor length- or weight-gainers. "In addition, the model does not accurately describe growth of breast-fed infants," says Janet M. Peerson, the statistician for the UC Davis international nutrition program. "Research indicates that healthy breast-fed babies are leaner than their formula-fed counterparts," she explains. Peerson notes that incorrect classification of breast-fed infants as faltering in growth may needlessly encourage mothers to cease nursing them. This is particularly harmful in developing countries where baby formula is expensive and alternative foods may not be sanitary. Peerson collaborated on this study with UC Davis nutrition professors Kathryn G. Dewey and Kenneth H. Brown. The findings of the study will be presented at the Nutritional Status Assessment III minisymposium, Tuesday, April 7, 9:30 a.m., Anaheim Convention Center, Room B1.