Weighing the Facts: A Systematic Review of Expected Patterns of Weight Loss in Full-Term, Breastfed Infants.

All breastfeeding infants lose some weight in the early days of life. Conventionally, 5% to 7% loss of birth weight has been accepted as the normal and expected amount of weight loss before infants begin to gain weight steadily. When infants lose more than 7% of their birth weight, breastfeeding adequacy is sometimes questioned and formula supplementation is often given. Despite the fact that 5% to 7% is well known and commonly cited, little reliable evidence exists that supports use of this figure as a guide to practice. A systematic review of studies that focused on infant weight loss was conducted. The main objective was to determine the mean amount of weight loss for healthy, full-term exclusively breastfed infants after birth. One previous review and 9 primary studies published since 2008 were examined. The reported mean infant weight loss ranged widely among studies from 3.79% to 8.6%. The point at which most infants have lost the most amount of weight occurs 2 to 4 days after birth. Close examination of the studies, however, revealed significant methodological flaws in the research. Study limitations commonly included gaps in data collection, lack of documented feeding type, sample groups that lacked adequate numbers of exclusively breastfed infants, and the exclusion of breastfed infants who lost the most weight. Well-designed clinical studies that address these limitations are needed.