The average weight of a 4-month-old baby varies from child to child but is generally double the infant's birth weight. Parents concerned about their child's weight should contact the baby's doctor.
Most pediatricians recommend starting a baby on solid foods when they're 6 months old, but some larger 4-month-old babies might not be satisfied on breast milk or formula. If the pediatrician approves, parents may start 4-month-old infants on solids as long as the baby has good head and neck control and can sit with support. A baby's first food should be rice cereal mixed with formula or breast milk. The mixture should be runny until the baby becomes used to it.