Breast fed babies have a mustard-like stool which may occur with every feeding initially. Gradually, they become less frequent to as few as one stool every few days. As long as the stool is soft, there is no need for concern. Bottle-fed babiesâ€™ stools are usually darker and more pasty. A certain amount of grunting and straining is to be expected when the baby passes stool. Constipation occurs when the stools are hard and infrequent. Conversely, diarrhea is frequent, watery stools. An occasional loose stool is normal.