OBJECTIVE: To evaluate the interobserver reproducibility of vascular indices obtained with three-dimensional power Doppler (3D power Doppler) ultrasonography at the first trimester of gestation. MATERIALS AND METHODS: The present reproducibility study involved 32 healthy pregnant women with 7 to 10 weeks and 6 days of gestation. The VOCAL (Virtual Organ Computer-aided AnaLysis) method was utilized to calculate embryos volume, with a 12° rotational angle. Subsequently, the software automatically displayed three 3D power Doppler vascular indices: vascularization index (VI), flow index (FI) and vascularization and flow index (VFI). In order to calculate the interobserver variability, an investigator performed a second blind measurement of the 32 embryos, and another investigator performed a third blind measurement of the same volumes. The interclass correlation coefficient (ICC) and Bland-Altman plots were utilized for statistical analysis. RESULTS: A good interobserver reproducibility was observed in relation to the three vascular indices. The VI presented ICC = 0.9 and mean difference between measurements = -1.1. For the FI, the ICC was 0.9 and mean difference = -0.5. The VFI presented ICC = 0.9 and mean difference = -1.1. CONCLUSION: The vascular indices, particularly the FI, obtained with 3D power Doppler ultrasonography at the first trimester of gestation demonstrated a high reproducibility.

Keywords: First trimester of gestation, Color Doppler ultrasonography, Reproducibility of results, Three-dimensional imaging

OBJECTIVE: To evaluate the correlation between the yolk sac volume measured by three-dimensional ultrasonography with gestational age at 7-10 weeks. MATERIALS AND METHODS: A cross-sectional study involving 72 healthy pregnant women at 7th-10th gestational weeks. The multiplanar method with 1.0 mm intervals was utilized. Regression models were constructed to analyze the correlation between yolk sac volume and gestational age, adjusted by the determination coefficient (R²). Mean, median, standard deviation, maximum and minimum values for yolk sac volume were calculated for each gestational age. RESULTS: A poor correlation was observed between yolk sac volume (YSV) and gestational age (GA). The quadratic regression was the model that best expressed this correlation: YSV = 0.9757 - 0.2499 × GA + 0.0172 × GA² (R² = 0.234). Mean yolk sac volume ranged from 0.07 cm³ (0.02-0.11) to 0.20 cm³ (0.02-0.74) between the 7th and 10th weeks (mean, 0.11 cm³, ± 0.10 cm³). CONCLUSION: There was a poor correlation between yolk sac volume and gestational age.

Keywords: Yolk sac, First trimester of pregnancy, Gestational age, Prenatal ultrasonography, Three-dimensional imaging