Your newborn’s first stools should be thick and black or dark green. This is the meconium, which is all the stuff your baby swallowed in your uterus.
Once the meconium is passed, your baby’s poop should be a mustard yellow color if he or she is being breastfed. If your baby is being fed formula, the poop should be the color of peanut butter.
Until your baby starts eating solid food, the stools will range from very soft to loose and runny. Babies who are fed formula tend to have firmer poops than babies who are breastfed.
Around 3 to 6 weeks, some breastfed babies will only have one poop a week, and this is fine. Babies who are fed formula should poop at least once a day.
A normal poop of a breastfed baby can look like diarrhea. You will know it is diarrhea if there is more than normal and if the stools are more watery.