Assess body proportionality – especially useful for newborns.
PI = (Weight in g / Length in cm³) × 100. Normal neonatal PI: 2.0–3.0. Unlike BMI, the ponderal index uses the cube of length, making it more appropriate for assessing proportionality in newborns. Low PI suggests asymmetric growth restriction (wasting). High PI may indicate macrosomia or maternal diabetes.