Reference ranges of the fetal ductus arteriosus area by Three-Dimensional ultrasonography

Objective To determine reference values for the fetal ductus arteriosus (DA) area using three-dimensional (3D) ultrasonography with spatio-temporal image correlation (STIC) in the rendering and multiplanar modes. Methods A prospective cross-sectional study was conducted with 322 cardiac volumes from normal fetuses between 20 and 33 + 6 weeks. DA area measurements were performed in the multiplanar (sagittal B-plane) and rendering modes. Polynomial regression models were fitted and assessed using the coefficient of determination (R 2 ). Reproducibility was assessed by the concordance correlation coefficient (CCC) and Bland-Altman plots, and agreement between modes by Bland-Altman analysis and least products regression. Results Patient age ranged from 18 to 45 years, with a median of 29.0 years. The median gestational age at the time of the ultrasound examination was 26.6 weeks (20.0–33.9 weeks). A linear relationship and a significant strong positive correlation were observed between gestational age and DA area measurements in the multiplanar and rendering modes (R 2 = 0.54 and 0.53, respectively). Mean DA areas in the multiplanar and rendering modes ranged from 0.06 to 0.32 cm 2 and 0.07 to 0.37 cm 2 , respectively. Intra- and interobserver reliability was good (CCC ≥ 0.72), but relative limits of agreement were wide. The rendering mode yielded larger areas (mean difference −0.028 cm 2 ). Conclusion Reference curves for the fetal DA area by 3D ultrasonography with STIC in the multiplanar and rendering modes were determined and showed a strong correlation with gestational age. These measurements showed good reliability but wide limits of agreement; the two modes are not interchangeable, and their clinical usefulness remains to be established.