A Comparison of UK Preterm Anthropometric Charts and INTERGROWTH-21st: Is It Time to Change Growth Charts?

Background: Current practice in the UK is to plot premature infant anthropometric measurements on Neonatal and Infant Close Monitoring (NICM) reference charts. These charts have several known limitations. The INTERGROWTH-21st Project has recently produced international ante- and postnatal growth standards. Exact knowledge of growth centiles allows clinicians to accurately assess infant nutritional requirements. Objective: To compare target centile measurements between INTERGROWTH-21st and UK NICM growth charts for premature infants. Method: Anthropometric measurements (weight and head circumference) of a convenience sample of neonates born between 24 and 32 weeks of gestation were analysed retrospectively. Measurements were collected across three time points and plotted on both the NICM and INTERGROWTH-21st growth charts. The respective centiles were compared and analysed by paired-sample t test, Wilcoxon rank test analysis, and multilevel mixed-effect linear regression models. Results: Centiles for weight and head circumference measurements of 96 infants plotted on INTERGROWTH-21st charts were significantly greater than their corresponding UK charts at all three time points. For weight, the average difference between the two charts varied from 9.1 to 16.4 centiles. The difference between the two charts was greater for female than male infants by up to 6.9 centiles (95% CI 10.1–3.8). Conclusion: Existing UK NICM reference charts are significantly different to the growth standards of INTERGROWTH-21st. The choice of which growth chart to adopt in the UK could have important consequences on premature infants’ future adult health and therefore requires further prospective observational studies with larger data sets including length measurements and more comprehensive population characteristics.