(1014) Diagnostic Performance of 32 vs 36 Weeks Ultrasound Predicting Late-Onset FGR and SGA Neonates

To investigate diagnostic performance of 32 weeks vs 36 weeks ultrasound in predicting late-onset fetal growth restriction (FGR) and small-for-gestational age (SGA) neonate.

Study Design: We searched PubMed, Scopus, and Web of Science systematically from inception until February 2022. We included studies in low-risk singleton pregnancies with screening ultrasound performed at 32 or 36 weeks. The estimated fetal weight (EFW) and abdominal circumference (AC) were assessed as index tests for the prediction of SGA (birthweight < 10^th centile) and FGR (EFW < 3 or EFW < 10). For the meta-analysis, hierarchical summary receiver-operating characteristic curves were constructed.

Results:

23 studies were included. Pooled sensitivities for EFW < 10 and AC < 10 for detecting 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. Pooled specificities for EFW < 10 and AC < 10 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. Observed diagnostic odds ratio (DOR) for EFW < 10 and AC < 10 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. 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 < 10 appeared to have comparable sensitivity, yet higher specificity and DOR than EFW < 10 in detecting SGA.

Conclusion: 36 weeks ultrasound appeared to have higher sensitivity and DOR with comparable specificity to 32 weeks ultrasound for EFW < 10 or AC < 10 in detecting SGA. However, the contrary was observed  in detecting FGR. Using different EFW cutoffs, our study identified EFW < 20 at 32 weeks as optimal cutoff in detecting SGA