Reference range for fetal interventricular septum area by means of four-dimensional ultrasonography using spatiotemporal image correlation

Objective: To determine reference range for fetal interventricular septum area by means of 3-dimensional ultrasonography (3DUS) using the spatiotemporal image correlation (STIC) method. Methods: A prospective, cross-sectional study was conducted on 328 normal pregnant women between the 18th and 33rd gestational weeks. To obtain the interventricular septum area, a virtual plane was used, with the green line (region of interest) adjacent to the external margin of the septum, which was manually delimited. To evaluate the correlation of the septum area with the gestational age, different regression modes were evaluated. The intraclass correlation coefficient was used to evaluate the interobserver reproducibility. Results: The interventricular septum area showed correlation with the gestational age (r = 0.81). The mean increased from 0.47 ± 0.10 cm² in the 18th week to 2.42 ± 1.13 cm² in the 33rd week of gestation. The mathematical equation that best represented this correlation was provided by linear regression: interventricular septum area = 0.0511 × gestational age (R² = 0.095). The interobserver reproducibility was good, with bias of 0.01 cm², precision of 0.07 cm² and absolute limits of agreement of -0.14 and +0.15 cm². Conclusions: Reference range for fetal interventricular septum area were determined by means of 3DUS using STIC in the rendering mode and were shown to be reproducible.