179 An outcome-based comparison of ISUOG vs SMFM guidelines for fetal growth restriction

Abstract

Recent international guidelines by the Society of Maternal Fetal Medicine (SMFM) and the International Society of Ultrasound in Obstetrics and Gynecology (ISUOG) differ in defining fetal growth restriction (FGR). Aim: To compare the prediction of small for gestational age (SGA) and a composite neonatal outcome using these varying definitions. This was a secondary analysis of data from a prospective study of women referred for 3rd trimester growth ultrasounds. SMFM and ISUOG guidelines were used to define FGR. SMFM defined FGR as EFW/AC < 10th percentile. ISUOG definition included EFW/AC < 3rd percentile and various Doppler parameters. The primary outcome was the prediction of neonatal SGA and a composite of neonatal morbidity and mortality by the two guidelines. Composite neonatal morbidity included Grade 3/4 interventricular hemorrhage, neonatal death, pH<7.1, seizure, NICU admission. Test characteristics (sensitivity, specificity, positive/negative predictive values (PPV/NPV), and positive/negative likelihood ratios (LR+/LR-), and area under the ROC curve (AUC) were determined. The association between the FGR and adverse neonatal outcomes were assessed using logistic regression. Of 1054 women meeting inclusion criteria, 137 (13.0%) and 80 (7.6%) were defined as having FGR by SMFM and ISUOG definitions, respectively. For prediction of SGA, the SMFM FGR definition had a higher sensitivity (54.7%) compared to the ISUOG FGR definition (38.1%). The ISUOG FGR definition had the highest specificity (97.1%). See table for full test characteristics. SMFM and ISUOG FGR definitions were similarly poor in predicting neonatal morbidity with sensitivities of 15.3% and 20.0%, respectively. Both SMFM and ISUOG FGR definitions were associated with low Apgar scores <7. The ISUOG FGR definition was associated with increased odds of cesarean for fetal distress. The SMFM guideline is associated with a higher detection rate for FGR but at the cost of reduction in specificity. Both definitions of FGR performed poorly at predicting a composite of neonatal morbidity.View Large Image Figure ViewerDownload Hi-res image Download (PPT)