Among infants who breastfed at least once, mean (±SD) weight nadir was 6.3±3.5% below birth weight, and 9.6% of the newborns lost ≥10% of birth weight. Among 2670 infants who lost ≥5% of their birth weight in the first 24 h, 782 (29%) eventually developed EWL, compared with 4840 (8%) of 57 109 infants who lost