Customized fetal growth standard compared with the INTERGROWTH-21st century standard at predicting...

The INTERGROWTH-21st project (IG-21) was recently performed aiming to provide a universal benchmark for comparing fetal growth across different ethnicities. Our aim was to compare the IG-21 with a customized standard for predicting pregnancies at risk for neonatal small-for-gestational age (SGA) and adverse outcomes.

This was a prospective cohort study including singleton pregnancies presenting for fetal growth assessment between 26 and 36 weeks of gestation. Fetal growth restriction was defined as estimated fetal weight <10th centile for gestational age using IG-21 and a customized standard. Neonatal SGA was defined as birthweight <10th centile for gestational age by the Alexander chart. Primary outcome was the prediction of neonatal SGA. Secondary outcomes included a composite of adverse neonatal outcomes. The discriminatory ability of each growth standard was compared using area under receiver operating characteristic curves (AUC).

Of 1054 pregnancies meeting the inclusion criteria, the incidence of neonatal SGA was 139 (13.2%), and a composite adverse neonatal outcome occurred in 300 (28.4%). The sensitivity of the customized standard (38.8%) was higher than that of IG-21 (24.5%) for predicting neonatal SGA, with AUC (95% CI) of 0.67 (0.63-0.71) for customized vs 0.62 (0.58-0.65) for IG-21; P = .003. Both standards were comparable in predicting the composite adverse neonatal outcomes: AUC (95% CI) 0.52 (0.50-0.55) for customized vs 0.51 (0.50-0.53) for IG-21; P = 0.25.

Both growth standards had modest performance in detecting neonatal SGA and were poor at predicting short-term adverse neonatal outcome.