Steps:
(1) Determine maternal overnight weight loss due to loss of breast milk and evaporation.
(2) Determine the infant's overnight weight gain taking into account known fluid input and output.
(3) Determine combined maternal and infant's evaporative weight loss, assuming that evaporative loss is related to metabolic body size (body weight taken to the power 0.73).
(4) Calculate the infant's evaporative weight loss.
(5) Calculate the infant's milk intake.
maternal overnight weight loss in grams due to evaporation and milk loss =
= (weight night before in grams) – (weight in morning) – (urine output in grams) – (stool output in grams) – (vomitus in grams) + (fluid intake in grams)
infant's overnight weight gain in grams due to evaporation and milk intake =
= (weight in morning in grams) - (weight night before in grams) + (urine output in grams) + (stool output in grams) + (vomitus or regurgitation in grams) - (fluid intake in grams)
combined maternal and infant's evaporative weight loss in grams =
= (maternal overnight weight loss in grams) – (infant's overnight weight gain in grams)
infant evaporative weight loss =
= (maternal and infant's evaporative weight loss) * ((infant's mean weight in grams)^0.73) / (((maternal mean weight in grams)^0.73) + ((infant's mean weight in grams)^0.73)) =
= ((maternal overnight weight loss in grams) – (infant's overnight weight gain in grams)) * ((infant's mean weight in grams)^0.73) / (((maternal mean weight in grams)^0.73) + ((infant's weight in grams)^0.73))
where:
• The mean maternal and infant's weight are the average of the night and morning weights.
• In Table 1, the after weight for the infant (A) should be 4,699; the 4,717 is the mean weight for 4,735 and 4,699.
milk intake in grams =
= (infant overnight weight gain in grams) + (infant evaporative weight loss in grams)
NOTE: This method depends on several assumptions which could affect the accuracy of the estimate. For example, it is assumed that there is no evaporation of urine from diapers nor loss through contact.
