Identification of intrauterine growth retardation among low birth weight preterm infants.

This study describes an attempt to define intrauterine growth retardation low birth weight preterm infants by comparing reference standards for intrauterine growth in weight, length, and head circumference on their variability across ethnic groups and cities, and on their specificity in independently classifying infants as short, thin, or having small heads. The sample consisted of 985 inborn preterm low birth weight infants enrolled at eight participating sites in a randomized clinical trial using uniform sampling criteria. When gestational age was used as the reference standard, striking differences were found by ethnicity and site in the prevalence of low weight infants at birth. These differences, as well as the potentially false overlap of classification, were attenuated when the use of gestational age as a reference standard was used only for birth length, while length itself was used (as an alternative to gestational age) as the reference standard for birth weight, and weight was used as the reference standard for head circumference. These results raise questions about the use of gestational age as the primary or only reference standard in assessing weight and head circumference at bith.