Reference curve of the fetal ventricular septum area by the STIC method: preliminary study.

Background: Early detection of septal changes such as septal hypertrophy commonly present in fetuses of diabetic mothers would help reduce the high rates of infant mortality.
Objective: Determine reference ranges for the fetal ventricular septal area through three-dimensional ultrasound (US3D) using the STIC method (Spatio-Temporal Image Correlation).
Methods: We conducted a cross-sectional study with 69 pregnant women between the 18th and 33rd weeks of pregnancy. We used as a reference the four-chamber plane with the ROI (Region of Interest) positioned from the ventricles; the septum area were manually marked. To assess the correlation of the interventricular septum area with gestational age (GA), we constructed scatter plots and calculated Pearson's correlation coefficient (r), and the adjustment was performed by the coefficient of determination (R²). We calculated averages, medians, standard deviations (sd), as well as maximum and minimum values. To calculate the intraobserver reproducibility, we used the intraclass correlation coefficient (ICC). The interventricular septum thickness was measured and it was correlated with gestational age and the septal area rendered in 52 patients using the ICC.
Results: The interventricular septum area was highly correlated with gestational age (r = 0.81), and the average increased from 0.47 cm² in the 18th week to 2.42 cm² in the 33rd of gestation. The intraobserver reproducibility was excellent with ICC = 0.994. No significant correlation was observed between the interventricular septum measurement and the GA (R² = 0.200), as well as there was no correlation with the septal area rendered with ICC = 0.150.
Conclusion: Reference intervals for the interventricular septum area between the 18th and the 33rd pregnancy week were determined to be highly reproducible.