PURPOSE: to evaluate the areas of the atrioventricular valves (tricuspid and mitral) of normal fetuses by the use of three-dimensional ultrasound (3DUS) and the spatiotemporal image correlation (STIC) method. METHODS: a cross-sectional study was conducted on 141 women between the 18th and the 33rd week of pregnancy. Cardiac volumes were measured with a volumetric transabdominal transducer attached to the Voluson 730 Expert equipment. The four chamber plane was used as reference, with the region of interest (ROI) positioned from the ventricles, and the area of the valves was obtained manually. To determine the correlation of the areas with gestational age, scatter plots were constructed and the Pearson correlation coefficient (r) was calculated. Means, medians, standard deviations (SD) and maximum and minimum values were calculated. The simple linear regression model was used to determine reference ranges of valve areas according to the gestational age by the Altman method, with the level of significance set at p<0.05. To calculate the intraobserver reproducibility, we used the intraclass correlation coefficient (ICC) and the Bland-Altman graph. RESULTS: the mitral and tricuspid valve areas were correlated to the gestational age (r=0.80 for the tricuspid and r=0.79 for the mitral valve) and the mean value of the tricuspid and mitral valves increased from 0.22±0.10 cm² and 0.23±0.10 cm² on the 18th week to 0.92±0.29 cm² and 1.08±0.41 cm² on the 33rd of pregnancy, respectively. The intraobserver reproducibility resulted in an ICC=0.993 (95%CI 0.987; 0.996) and the mean difference was 0.01 cm² (SD±0.2 cm² and CI95%±0.4 cm²). CONCLUSION: reference intervals for the areas of the mitral and tricuspid valve between the 18th and the 33rd week of gestation were determined and proved to be highly reproducible.
Fetal heart; Pregnancy; Heart valves; Reference ranges; Imaging, three-dimensional
