When Growth Patterns Change
Typically, babies establish a steady growth pattern within the first six months of life. But occasionally, a baby's growth may deviate from its formerly steady pattern. For example, a baby who has been in the 80th percentile for weight may drop to the 65th percentile as of his most recent checkup. Although "falling off the curve" can potentially be the sign of a health problem, most often the change is not call for alarm.
Assuming your child is otherwise healthy, the drop in percentile could just mean that your baby's weight or height is adjusting to his intended genetic size. For example, a baby who was born quite small because of various influences in the womb may shift growth curves during his first 18 months of life to match the percentile of his relatively large parents.
Besides genetics, your baby's activity level can cause a slowdown in her weight gain. A baby who has just begun crawling, cruising, or walking will burn many more calories than a young infant who spends the bulk of her time sitting in one place. Moreover, a baby who has realized her capacity to explore the wonders of the world may find herself too distracted to stop and eat!
Last, illness has the potential to reduce your baby's weight and change her growth pattern temporarily. Fever or a period of diarrhea and/or vomiting can cause a baby to lose fluid, and her weight may decrease. However, generally, a mild illness like a cold will not impact a baby's overall growth rate.
Of course, although most shifts in a child's growth pattern can be explained by normal life changes, you should always tell your pediatrician about any concerns regarding your child's development. If there's no obvious reason for the change, she'll want to evaluate things further.