The close monitoring of anthropometric changes is integral to the nutritional care of newborns. The postnatal growth patterns of newborns differ by both size and gestational age. Thus, an early step in monitoring anthropometric changes involves classifying the newborn infant.
Size categories for birth weight are adequate birth weight (≥2,500 g), LBW (<2,500 g), and, within the LBW group, VLBW (<1,500 g). Gestational age categories include preterm (≤37 weeks), full term (38 to 42 weeks), and post term (>42 weeks). Clinical obstetric estimation of gestational duration is based on maternal dates and on ultrasound examination. Gestational duration can also be estimated from physical examination of the infant, using the examinations by Dubowitz and colleagues47 or Ballard and coworkers48 for larger infants of more than 30 weeks' gestational age,49 or using the more recent Ballard examination50 for extremely low-birth-weight infants.
Reference values are available for normal birth weight, length, and head circumference at different gestational ages (see, e.g., Babson 51 and the review of growth curves by Sparks5). Based on the reference values used, infants are generally classified as appropriate for gestational age (AGA), small for gestational age (SGA), or large for gestational age (LGA).
Accurate anthropometric measurements made at appropriate intervals provide information that is crucial for clinical decision making in the intensive care unit (see, e.g., Kaempf and colleagues52). These measurements require that well-trained personnel use standardized techniques and accurate equipment, such as a well-calibrated digital scale. Quality control procedures should be in place to ensure accurate measurements over time.
It is important to plot changes in weight, length, and head circumference on appropriate grids. Adaptations of the classic weight curves by Dancis53 are widely used for this purpose (see, e.g., Hay4). Other postnatal growth charts are available (e.g., Babson and Benda54 and Gairdner and Pearson55). Alternatively, many centers plot longitudinal changes in length and head circumference on intrauterine charts (e.g., Lubchenco and colleagues56). Plotting the data facilitates the identification of infants who are growing slower or faster than the expected patterns. As with other nutrition-related decisions, such determinations may require sophisticated judgments by an experienced team.