Up to 10 percent of children who visit primary care settings have failure to thrive, usually due to behavioral or psychosocial issues, according to the American Family Physician. For example, babies and moms may struggle with breast-feeding, or parents may unnecessarily avoid giving their children high-calorie foods when weaning off formula or breast milk. In these cases, failure to thrive is called “inorganic,” and is identified through an evaluation of the children's eating habits and interactions with their parents.
Rather than related to a medical condition, inorganic failure to thrive is "caused by environmental factors, psychosocial problems, neglect – either accidental or, on the rare occasion, not accidental neglect,” says Jenifer Thompson, a pediatric dietitian at Johns Hopkins Children's Center. “So it’s when you actually don’t have enough food or you don’t have the proper amounts of food or breast milk or formula.”
Less often, failure to thrive is “organic,” meaning it is a symptom of a condition or disease that causes malnutrition. For instance, some children with gastroesophageal reflux don’t keep enough food down, while children with celiac disease don't absorb enough nutrients. Conditions such as thyroid disease and congenital heart disease can also be culprits, since they may cause children to burn too many calories.
Sometimes, failure to thrive is applied to children who end up being healthy, just small. Other times, babies who were overnourished in utero are born bigger but gain weight more slowly. In that case, they deviate downward from the growth curve but can wind up healthy, too.
“The main thing is to determine what the problem is – and sometimes, it’s not a problem at all,” Watterberg says.