Every pumping session is a new session. Calories in breast milk range from 13-35 calories per ounce. The average amount of calories in typical breast milk around 20-22 calories. This fluctuation is due to changing fat content. The amount of fat in human milk changes depending on the degree of emptyness of the breast (empty breast = high fat, full breast = low fat). The longer a mom goes between pump sessions, the more water is in the milk and the lower the fat content. This is because the mom’s body thinks the baby is getting dehydrated and the water content is to rehydrate the baby. A breastfeed baby can take in the same amount of calories from different volumes of milk. For example, 4 ounces of 15 calorie pumped milk early in the morning has the same calories as 3 ounces of 20 calorie breastmilk pumped only a few hours later. This is unlike formula. Standardized formula has 20 calories per ounce.
For more info on the nutrition facts in breastmilk, check out these websites!!