After birth, it is expected that your baby will produce the first stool within 24 hours. The first bowel movements (BM's) are dark green or black as the baby passes meconium, the substance filling the intestines before birth. In a few days, you’ll notice greenish stools signifying intestinal colonization by the friendly bacteria that start to take an active role in digestion.
Breast-fed infants typically have more BM's than their formula-fed peers because breast milk is digested very quickly. Their stools are runny and look like yellow mustard with a seedy appearance. Breast-fed babies rarely get constipated.
Digestion of infant formula produces more waste. Infants who drink formula pass malodorous, firmer, yellow, green, or mocha stools. Since formula is a little harder to digest, do not be surprised if your baby gets constipated.
Not every baby goes by the textbook though. So keep in mind that stools in any shade of yellow, yellow-brown, and brown are perfectly normal.
I get concerned with 3 colors of stools: red (fresh blood), black beyond the first few days of life (old blood), and white (blockage in the bile system). Should you notice any of these colors in your infant’s diapers, seek evaluation of your pediatric health care provider immediately.