Doctors diagnose failure to thrive when children's weight or the rate at which they gain weight falls far below that of children of the same gender and similar height, according to the Johns Hopkins Children's Center. Both medical and environmental factors can cause children to fail to thrive.
A child who fails to thrive shows symptoms such as a weight below the third percentile on standard growth charts, which is 20 percent below the ideal weight for a child of the same height, as the Johns Hopkins Children's Center explains. Shorter heights and smaller head circumferences are also symptoms of failure to thrive, and other effects include delayed development of physical skills such as rolling over and walking. Children who fail to thrive may also exhibit mental and social skills that do not develop as quickly as those of other children.
Cerebral palsy, Down syndrome, Turner syndrome, damage to the central nervous system and gastrointestinal problems are medical causes of failure to thrive, notes the Johns Hopkins Children's Center. Poor nutrition, exposure to infections or toxins, and emotional deprivation are environmental causes of failure to thrive. In many cases, doctors cannot pinpoint the exact cause of a child's failure to develop at the same rate as other children. Doctors treat failure to thrive based on whether medical or environmental factors caused the condition.