The criteria to classify body-proportionality of the small for gestational age newborn: a scoping review.

Purpose: To create an overview of the criteria used to classify small for gestational age (SGA) newborns according to their body-proportionality as either asymmetric SGA or symmetric SGA, and to create an overview of the clinical outcomes related to body-proportionality.

Methods: A scoping review was conducted using PubMed, Embase and the Cochrane Library databases. Studies were included if they described SGA newborns regardless of gestational age and if their classification on body-proportionality was given for both aSGA and sSGA. Data were screened and extracted by two independent reviewers.

Results: Of the 38,265 studies identified after deduplication, 45 were included. Body-proportionality was classified by the ponderal index (PI) in 55.6% of studies (n = 25), head circumference (HC) in 24.4% (n = 11), birth length in 11.1% (n = 5), birth length and HC in 4.4% (n = 2), birth length and PI in 2.2% (n = 1), and PI, brain-to-body ratio and HC/length ratio in 2.2% (n = 1). The most commonly reported outcomes were asphyxia, hyperbilirubinemia, hypoglycemia, mortality and respiratory distress syndrome. The results regarding the outcomes were inconsistent and contradictory.

Conclusion: Large heterogeneity in the published classifications and clinical outcomes regarding body-proportionality in the SGA newborns exists. Consensus on terms, methods and cut-off values used for body-proportionality is needed to improve future comparison of study results.