The Auxological and Biochemical Continuum of Short Children Born Small for Gestational Age (SGA) or with Normal Birth Size (Idiopathic Short Stature)

Objective. Retrospective single-centre analysis of growth characteristics in 182 healthy short children born small for gestational age (SGA) or appropriate for gestational age (idiopathic short stature, ISS). Methods. Birth size references from the USA and Sweden were compared, and for the classification as SGA or ISS the Swedish reference was chosen. Height, target height (TH), bone age (BA), predicted adult height (PAH), IGF-I and IGFBP-3 values were compared between SGA and ISS. Results. In the combined group, birth weight and length showed a symmetric Gaussian distribution. The American reference overestimates the percentage of short birth length and underestimates that of low birth weight. In childhood, SGA children were shorter than ISS (−3.1 versus −2.6 SDS, P < .001), also in comparison to TH (−2.6 versus −1.9 SDS, P < .001). TH, height SDS change over time, BA delay, and PAH were similar. IGF-I and IGFBP-3 were lower in ISS (P = .03 and .09). Conclusions. SGA children represent the left tail of the Gaussian distribution of birth size in short children. The distinction between SGA and ISS depends on birth size reference. Childhood height of SGA is lower than of ISS, but the other auxological features are similar.