Performance of the Intergrowth-21st and World Health Organization fetal growth charts for the detection of small for gestational age neonates in a population from Latin America

Abstract

Objective: To evaluate the performance of INTERGROWTH-21st and World Health Organization (WHO) fetal growth charts to identify small-for-gestational-age (SGA) and fetal growth restriction (FGR) neonates as well as their specific risks for adverse neonatal outcomes. Design: Multicenter cross-sectional study. Setting: Ten maternity units across four Latin American countries, 2016-2018. Population: 67,968 singleton live births. Methods: According to each standard, the neonates were classified as SGA and FGR (birthweight <10th and <3rd centiles, respectively). Main Outcomes Measures: The relative risk (RR) and diagnostic performance for the occurrence of a low Apgar score and low ponderal index were calculated for each standard. Results: The WHO charts identified more neonates as SGA than IG-21st (13.9% vs. 7%, respectively). 6.9% babies were considered SGA only by the WHO chart. Compared to normally grown babies, neonates classified as FGRs by both standards had the highest RR for a low Apgar (RR: 5.57; 95% CI: 3.99–7.78), followed by those SGA by both curves (RR: 3.27; 95% CI: 2.52–4.24), while SGAs identified by WHO alone did not have an additional risk (RR: 0.87; 95% CI: 0.55–1.39). Furthermore, the diagnostic odds ratio for a low Apgar was higher when INTERGROWTH-21st was used than when SGA and FGR were defined by WHO charts. Conclusions: In a large population of singleton deliveries from Latin America, the WHO fetal growth charts seem to identify significantly more SGA neonates than the INTERGROWTH-21st charts, but the diagnostic performance of the latter for low Apgar score and low ponderal index is better.