How often do you need to change baby’s diaper? Your newborn will pass meconium for their first few days of life. This is a black, sticky substance. By the third day, their poop will turn to a runnier, lighter stool. How often you’ll need to change their diaper varies depending on whether or not you’re breastfeeding or formula-feeding them. Breastfed babies will typically have several bowel movements per day. Formula-fed babies will have fewer. Either way, you’ll want to change your baby’s diaper every two to three hours. If the diaper is just wet with urine, you don’t need to change it right away and wake up your sleeping baby. However, change baby immediately following any bowel movements to avoid irritation. You can tell it’s time to change your baby’s diaper as soon as you can smell or feel that they’ve had a bowel movement. To determine if the diaper is wet, put one hand on the diaper to feel if it’s damp. Alternatively, some diapers change color when they’re wet.