Diagnostic performance of 32 vs 36 weeks ultrasound in predicting late-onset fetal growth restriction and small-for-gestational-age neonates: a systematic review and meta-analysis

Abstract

ObjectiveFetal growth restriction (FGR) is an independent risk factor for fetal death and adverse neonatal outcome. The main aim of this study was to investigate the diagnostic performance of 32 weeks vs 36 weeks ultrasound of fetal biometry in detecting late-onset FGR and predicting small for gestational age (SGA) neonate. Data sourcesA systematic search was performed to identify relevant studies published until June 2022, using the databases PubMed, Web of Science, and SCOPUS. Study eligibility criteriaWe used cohort studies in low-risk or unselected singleton pregnancies with screening ultrasound performed at ≥32 weeks of gestation. Study appraisal and synthesis methodsThe estimated fetal weight (EFW) and abdominal circumference (AC) were assessed as index tests for the prediction of SGA (birthweight <10th centile) and detecting FGR (EFW<10th centile and/or AC<10th centile). The quality of the included studies was independently assessed by two reviewers, using the Quality Assessment of Diagnostic Accuracy Studies-2 tool. For the meta-analysis, hierarchical summary Area Under the receiver-operating characteristic curves (AUROC) were constructed and quantitative data synthesis was performed using random-effects models. ResultsThe analysis included 25 studies encompassing 73,981 low-risk pregnancies undergoing third-trimester ultrasound assessment for growth of which 5380 (7.3%) were SGA at birth. The pooled sensitivities for EFW<10th and AC<10th centiles for predicting SGA were 36% (95% CI 27-46%), 37% (95% CI 19-60%), respectively at 32 weeks and 48% (95% CI 41-56%), 50% (95% CI 25-74%), respectively at 36 weeks. The pooled specificities for EFW<10th and AC<10th centiles for detecting SGA were 93% (95% CI 91-95%), 95% (95% CI 85-98%), respectively at 32 weeks and 93% (95% CI 91-95%), 97% (95% CI 85-98%), respectively at 36 weeks. The observed diagnostic odds ratio (DOR) for EFW<10th and AC<10th centiles for detecting SGA were 8.8 (95% CI 5.4-14.4%), 11.6 (95% CI 6.2-21.6), respectively at 32 weeks and 13.3 (95% CI 10.4-16.9), 36 (95% CI 4.9-260), respectively at 36 weeks. The pooled sensitivity, specificity, and DOR in predicting FGR at 32 weeks were 71% (95% CI 52-85%), 90% (95% CI 79-95%), and 25.8 (95% CI 14.5-45.8), respectively vs 36 weeks were 48% (95% CI 41-55%), 94% (95% CI 93-96%), and 16.9 (95% CI 10.8-26.6), respectively. AC<10th centile appeared to have comparable sensitivity to EFW<10th in predicting SGA neonates ConclusionAn ultrasound assessment of the fetal biometry at 36 weeks appeared to have better predictive accuracy for SGA neonates compared to an ultrasound at 32 weeks. However, opposite trend was noted when the outcome was FGR. Fetal AC had a similar predictive accuracy to that of EFW in detecting SGA neonates.