Dietary changes can affect the frequency and consistency of your baby’s stools. These dietary changes include: switching from breast milk to formula, switching formulas, and adding solid foods to the diet. It sometimes may take up to a week for a baby’s digestive system to “learn” a new food. Changes in a baby’s diet including change from breast milk to formula will result in stool color changes and this is normal. As for stool consistency, the stools of breastfed babies are usually soft and more “mushy” whereas formula fed infants have slightly firmer stools. The stools of breastfed babies are also more frequent than babies on formula. It is not uncommon for babies to go several days without having a bowel movement. Grunting and grimacing during a bowel movement are often just baby’s way of experiencing the use of the various muscles associated with having a bowel movement. We recommend checking with your baby's HCP if your baby does not adjust to the new formula &/or if baby is in pain, cries when trying to have a bowel movement or if there is blood in his or her stool.