Effect of Maternal Obesity on Fetal Interventricular Septum Volume: A Three-Dimensional Ultrasound STIC and VOCAL Study

Objective: To assess correlations between maternal obesity and fetal interventricular septum (IVS) volume measured by means of spatiotemporal image correlation and Virtual Organ Computer-Aided Analysis (STIC-VOCAL), after adjustment for gestational age. Methods: This cross-sectional observational study included 88 consecutive singleton pregnancies undergoing routine obstetric ultrasound at our center between January 2024 and December 2025. Fetal IVS volume was assessed using STIC-VOCAL, and its association with maternal characteristics was evaluated by means of univariate and multivariable regression analyses adjusted for gestational age. Results: Fetal IVS volume increased with estimated fetal weight (r = 0.860, p < 0.0001) and gestational age (r = 0.891, p < 0.0001), which represented the main determinant of absolute fetal cardiac volume. The association between maternal obesity and fetal IVS volume was not evident on univariate analysis (U = 987.5, p = 0.874) but became significant after adjustment for gestational age in multivariable regression models (β = +89.1 mm3, p < 0.0001). At comparable gestational ages, maternal obesity was associated with an adjusted increase in fetal IVS volume of approximately 22.6 mm3. Conclusions: Maternal obesity was independently associated with a modest increase in fetal IVS volume after adjustment for gestational age. STIC-VOCAL volumetry may provide a sensitive tool for detecting subtle fetal cardiac structural changes, although these findings remain exploratory.