Color. A newborn's first bowel movements usually consist of a thick, black or dark green substance called meconium (pronounced mi-KOH-nee-uhm). After the meconium is passed, the stools ("poop") will turn yellow-green. The stools of breastfed infants look mustard-yellow with seed-like particles.

Consistency. Until the infant starts to eat solid foods, the consistency of the stool can range from very soft to loose and runny. Formula-fed infants usually have stools that are tan or yellow in color and firmer than those of a breastfed infant. Whether your baby is breastfed or bottle-fed, hard or very dry stools may be a sign of dehydration.

Frequency. Infants who are eating solid foods can become constipated if they eat too many constipating foods, such as cereal or cow's milk, before their system can handle them. The U.S. Food and Drug Administration (FDA) and the American Academy of Pediatrics (AAP) do not recommend cow's milk for babies under 12 months.

Because an infant's stools are normally soft and a little runny, it's not always easy to tell when a young infant has mild diarrhea. The main signs are a sudden increase in the number of bowel movements (more than one per feeding) and watery stools.

Diarrhea can be a sign of intestinal infection, or it may be caused by a change in diet. If the infant is breastfeeding, diarrhea can result from a change in the mother's diet. The main concern with diarrhea is the possibility that dehydration can develop. If fever is also present and your infant is less than 2 months old, you should call your health care provider. If the infant is over 2 months old and the fever lasts more than a day, check the infant's urine output and rectal temperature and consult a health care provider. Make sure the infant continues to feed often.

Starting around the age of 3 to 6 weeks, some breastfed babies have only one bowel movement a week. This is normal because breast milk leaves very little solid waste to pass through the digestive system. Formula-fed infants should have at least one bowel movement a day. If a formula-fed infant has fewer bowel movements than this and appears to be straining because of hard stools, constipation may be the cause. Check with your health care provider if there are any changes in or problems with your infant's bowel movements.