There is no scientific basis to the idea that cold milk would upset a baby's stomach more than warmed milk. In fact, warming milk has been shown to deprive the milk of some of it's nutritional content. The CDC's guidance is:

Breast milk does not need to be warmed. It can be served room temperature or cold.

However, the CDC notes the fatty layer of the milk tends to separates when the milk is chilled thus reducing the nutritional value of the milk to your baby. This is easily solved by shaking the milk when removing it from the refrigerator.

The OWH corroborates this as well in their guidelines.

Similarly, cold milk will release less of it's aromatics. For breast milk when the mother has been on a bland diet, this can cause chilled milk to be less enticing to a baby. Most babies prefer a bottle due to the ease at which they can extract the milk and is one of the greatest causes of failure for those who want to breast feed, thus anything one can do to make bottle feeding less comfortable for them (such as feeding them cold milk) is often cited as an advantage in a breastfeeding plan.

Conversely, mothers consuming pungent foods such as onions, curries, asparagus etc will often see a decrease in the baby's desire to feed due to the pungent aromatics making their way into the breast milk. Chilling the milk will help mask these chemicals.

There is no scientific basis to the idea that cold milk would upset a baby's stomach more than warmed milk.

Per the CDC:

Breast milk does not need to be warmed. It can be served room temperature or cold.

However, the CDC recommends to

Swirl the breast milk to mix the fat, which may have separated.

Cold milk will release less of it's aromatics. For breast milk when the mother has been on a bland diet, this can cause chilled milk to be less enticing to a baby. Most babies prefer a bottle due to the ease at which they can extract the milk and is one of the greatest causes of failure for those who want to breast feed, thus anything one can do to make bottle feeding less comfortable for them (such as feeding them cold milk) is often cited as an advantage in a breastfeeding plan.

Conversely, mothers consuming pungent foods such as onions, curries, asparagus etc will often see a decrease in the baby's desire to feed due to the pungent aromatics making their way into the breast milk. Chilling the milk will help mask these chemicals.

There is no scientific basis to the idea that cold milk would upset a baby's stomach more than warmed milk. In fact, some parents find the opposite is true.

However, there is some evidence that the fatty layer of the milk tends to separates when the milk is chilled thus reducing the nutritional value of the milk to your baby. This is easily solved by shaking the milk when removing it from the refrigerator.

Similarly, cold milk will release less of it's aromatics. For breast milk when the mother has been on a bland diet, this can cause chilled milk to be less enticing to a baby. Most babies prefer a bottle due to the ease at which they can extract the milk and is one of the greatest causes of failure for those who want to breast feed, thus anything one can do to make bottle feeding less comfortable for them (such as feeding them cold milk) is often cited as an advantage in a breastfeeding plan.

Conversely, mothers consuming pungent foods such as onions, curries, asparagus etc will often see a decrease in the baby's desire to feed due to the pungent aromatics making their way into the breast milk. Chilling the milk will help mask these chemicals.

There is no scientific basis to the idea that cold milk would upset a baby's stomach more than warmed milk. In fact, warming milk has been shown to deprive the milk of some of it's nutritional content. The CDC's guidance is:

Breast milk does not need to be warmed. It can be served room temperature or cold.

However, the CDC notes the fatty layer of the milk tends to separates when the milk is chilled thus reducing the nutritional value of the milk to your baby. This is easily solved by shaking the milk when removing it from the refrigerator.

The OWH corroborates this as well in their guidelines.

Similarly, cold milk will release less of it's aromatics. For breast milk when the mother has been on a bland diet, this can cause chilled milk to be less enticing to a baby. Most babies prefer a bottle due to the ease at which they can extract the milk and is one of the greatest causes of failure for those who want to breast feed, thus anything one can do to make bottle feeding less comfortable for them (such as feeding them cold milk) is often cited as an advantage in a breastfeeding plan.

Conversely, mothers consuming pungent foods such as onions, curries, asparagus etc will often see a decrease in the baby's desire to feed due to the pungent aromatics making their way into the breast milk. Chilling the milk will help mask these chemicals.