During the progression of failure to thrive (FTT) in infants, which growth measurement is typically the first to decline?

In the context of failure to thrive (FTT) in infants, weight is typically the first growth measurement that shows a decline. This occurs because weight is directly related to nutritional intake. When an infant is not receiving adequate nutrition, whether due to inadequate calorie intake, malabsorption, or increased energy expenditure, weight changes are usually the most immediate response.

In clinical practice, weight measurements are closely monitored in infants. When there is a decrease in weight-for-age percentile, it can be an early indicator of potential issues, prompting further investigation into dietary intake and underlying health conditions.

Height and head circumference can also be affected by inadequate nutrition, but these measurements may remain stable for longer periods before showing declines. This is particularly due to the body's prioritization of growth in length and head circumference when nutritional deficiencies are mild. Therefore, weight is a crucial measurement in the early detection of failure to thrive and is often the first sign that an infant's growth pattern is deviating from expected norms.