Comparison of SGA and Severe SGA rates using six size standards - Is there a difference?

ABSTRACT

BACKGROUND: Small for gestational age (SGA) neonates are known to be at an elevated risk for neonatal morbidity. Despite this, there is a growing array of proposed size standards for identifying SGA fetuses. Given the inherent differences in design, acquisition methods, and the characteristics of the populations they represent, the generalizability of these standards to diverse populations remains uncertain. INTRODUCTION: This study aimed to assess variations in rates of SGA and severe SGA using six distinct size standards Hadlock, Fetal Medicine Foundation (FMF), World Health Organization (WHO), Intergrowth-21 (IG-21), and two locally derived population-based size standards. The objective was to examine the differences in SGA and severe SGA rates among these size standards. METHODS: A retrospective cohort study was conducted, encompassing all singleton deliveries in two tertiary referral hospital campuses with an annual birth count exceeding 10,000, from January 2019 to July 2022. SGA and severe SGA were defined as birthweights below the 10th or 3rd percentile, respectively, based on each growth standard. The study design included details on the setting, subjects (singleton deliveries), and the chosen size standards. Comparative analyses were performed to assess variations in SGA and severe SGA rates among these size standards. RESULTS: Our study analyzed 32,912 singleton deliveries. We found that the choice of growth standard significantly impacted the rates of both SGA and severe SGA infants. Notably, the WHO criteria identified 5,548 (16.9 %) fetuses as SGA, compared to only 1,716 (5.2 %) using the INTERGROWTH-21 standard (p < 0.001). Similarly, for severe SGA, the FMF charts classified 2098 (6.37 %) infants, significantly higher than the 320 (1 %) identified by Dolberg's local population-based charts (p < 0.001). CONCLUSION: Our study demonstrates a significant variety of SGA and severe SGA rates using different size standards. Therefore, the decision on the size standards in use is critical given the significant influence on clinical management. SYNOPSIS There are significant variations in SGA and Severe SGA rates depending on the chosen size standard.