Once started on formula, it may become difficult to go back to breast feeding on a regular basis. When a mother first starts to breastfeed, she may be worried that she will not have enough milk for the baby. Her breasts are just starting to fill up with a creamy, yellowish substance that is called colostrum. The regular breast milk will not come in for three to five days. Sometimes this can take longer.
Colostrum contains more protein and less fat than regular breast milk.
Secretions of colostrum are generally small, but during this time the baby does not need much fluid. The colostrum will provide for adequate nutrition. It is actually very important that the milk does not fill the breasts right away. This would make it difficult for the baby to suck well enough to empty them out. If you do not have enough milk for the first few days, you should not worry about it.