A newborn is expected to lose some weight during the first five to seven days of life. The American Pregnancy Association suggests that a 5 percent loss is normal for formula fed newborns and a 7 to 10 percent loss for breastfed babies. Sometime between days 10 and 14 after birth, the infant will return to birth weight. Parents can monitor this at home. Or, routine pediatric appointments will include weighing the baby and calculating the percentage of weight loss.
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Record the infant's weight at birth.
Place the completely undressed baby on an infant scale.
Wait for the baby to lie still before noting the number on the scale.
Subtract the current weight from the birth weight. This is the amount of weight lost.
Divide the weight loss number by the birth weight and multiply it by 100 to get a percentage.