Current practices in neonatal intensive care units involve the routine use of growth charts to track and identify patterns in the growth of preterm infants. Perhaps the most popular growth chart in use today is the Fenton Growth Chart. To interpret this chart, a patient's growth curve is plotted over a set of standard curves (typically representing the 10th, 25th, 50th, 75th and 90th weight-for-age centile). The curves are then visually compared to identify patterns in growth (adequate, slow, or catch-up growth). Patterns in neonatal growth may be subtle and current growth curves may be prone to misinterpretation. This may be due to biases inherent in the human visual perception system, including the difficulty in visually estimating slopes and angles between two curves.