Appearance: The very first BMs are a thick black or greenish substance called meconium.
Frequency: Babies produce stool at least once a day during the first week. The meconium stage lasts only a few days.
Newborn to 2 Months
Appearance: After the meconium phase, stools are yellowish green. Breast-fed babies pass mustard- or gold-colored stools with seedlike particles; they tend to be soft but can vary from relatively firm to quite runny. Formula-fed babies tend to have slightly deeper colored and firmer stools but still softer than an older child’s or adult’s.
Frequency: Some babies have a BM with each feeding; less often is normal, too. By 3 to 6 weeks, some breast-fed newborns soil a diaper just once a week. Formula-fed newborns poop at least once a day.
2 to 3 Months
Appearance: Stool becomes more solid now that your baby’s intestines can hold more, and he’s absorbing more nutrients from breast milk or formula.
Frequency: As his gastrointestinal system matures, your baby won’t need to poop as often. Stool frequency may vary from several per day to once every three to four days is average for formula-fed babies, and for breast-fed babies it may be as infrequent as once a week.
4 to 12 Months
Appearance: Once your baby starts eating solids, get ready for Technicolor poop! Stool can take on the hues of food, while the sugars and fats in food may give stool a stronger odor. It’s also normal to see pieces of undigested food.
Frequency: BMs vary a lot from child to child. If your baby grunts or turns red in the face while having a bowel movement, that's normal. It's also normal for some breastfed babies to go four to seven days without one.
If your child goes without a BM for longer periods than those listed here, or seems to be in pain or straining, check with his doctor about constipation. Other signs of digestive trouble include stool that’s extremely watery or loose (especially after the first month of life) and stool that contains mucus or blood.