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Serial measurements of weight, length, and head circumference allow for evaluation of growth patterns.

  1. Weight. Birthweight (BW) is reflective of maternal, placental, and fetal environment. Both term and preterm neonates experience weight loss after birth (approximately 10%, or higher in preterm infants) due to loss of extracellular free water. Term infants regain birth weight by 7 to 10 days, whereas preterm infants may take 10 to 15 days to regain birth weight (or even longer in extremely low BW [ELBW] infants). Once BW is reached, average daily weight gain should be 14 to 20 g/kg/d for preterm infants and 20 to 30 g/d for term infants.

  2. Length. Length is a better indicator of lean body mass and long-term growth and is not influenced by fluid status. Weekly assessment is recommended using a neonatal length board. Average length gain is 1.4 cm/wk in preterm infants and 0.7 cm/wk in term infants.

  3. Head circumference. Occipitofrontal circumference (OFC) reflects brain growth and correlates with long-term neurodevelopment. Weekly assessment is recommended. Preterm infants grow at a rate of 0.9 cm/wk and term infants at 0.33 cm/wk. Premature infants exhibit catch-up growth in head circumference that may exceed normal growth rate, but an increase in head circumference >1.25 cm/wk may be abnormal and should prompt evaluation for hydrocephalus or intraventricular hemorrhage. Poor head circumference growth may reflect underlying poor nutritional status or medical condition and may be associated with motor and cognitive delays.

  4. Weight for length. This reflects symmetry of growth. Current weight expressed as a percentage of ideal weight for length can identify infants at risk for under- or overnutrition. Catch-up growth occurs faster if only weight is lagging compared with length and head circumference. Weight gain is slower in large for gestational age infants.

  5. Z-scores. Z-scores express anthropometric data as a function of standard deviation from the mean or median value and can be used to compare weight for age, weight for height, and height for age across various ages; they are useful for comparing populations.

  6. Body composition. Body mass index (BMI) for gestational age reference curves allow assessment of proportionality of weight and length growth. BMI and weight for length show high agreement. Body mass composition curves for healthy preterm infants at birth assess patterns of fetal body composition variation and can identify infants at risk for metabolic syndrome.

  7. Growth velocity. Growth velocity is higher at earlier gestational age; at <27 weeks, it is approximately 20 g/kg/d; at 33 weeks, approximately 14 g/kg/d; and at term, approximately 10 g/kg/d. Fetal growth velocity approximates 1% to 3% of body weight per day.


  1. Measurements. Weight, length, and head circumference are plotted on growth charts to facilitate comparison with established norms.

  2. Growth charts. Growth can be monitored longitudinally on standard growth charts. For term infants, the World Health Organization (WHO) growth charts (2006) based on data from different ...

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