Failure of an infant, toddler, or child to grow at a normal rate. Related terms include malnutrition, growth hormone deficiency, low birth weight, and short stature.

Failure to thrive (FTT) occurs when an infant, toddler, or child fails to grow at a normal rate, either due to organic (genetic) or environmental causes. Growth is measured as a combination of factors, including age, weight, height, and sometimes bone age. The height and weight of a child can vary widely at a particular age and still be considered normal. According to the National Center for Health Statistics standards, FTT is formally diagnosed when the child's weight is below the fifth percentile for his age (i.e., he or she is smaller than 95% of others his age) or when the weight drops more than two percentile groups. Low height alone or slightly low height with...