Assessing Fetal Circulatory Changes in Gestational Diabetes via Aortic Isthmus Doppler

Background: Gestational diabetes mellitus (GDM) is a common complication during pregnancy that can negatively impact fetal heart function and structure. This study aimed to investigate the hemodynamic characteristics of the fetal aortic isthmus in patients with GDM using Doppler ultrasound parameters. Methods: This was a cross-sectional observational study including 47 pregnant patients with GDM and 47 healthy pregnant patients as controls. Fetal biometric measurements and umbilical artery Doppler values were obtained. Aortic isthmus Doppler was used to measure systolic and diastolic flow velocity time integrals (S and D), peak systolic velocity (PSV), and systolic nadir (Ns) to calculate the isthmus flow index (IFI) = (S + D)/S and isthmus systolic index (ISI) = Ns/PSV. A generalized additive model was used to analyze the relationship between IFI, ISI and gestational age. Results: Compared to controls, the GDM group had significantly lower D (2.39 cm vs. 2.76 cm), Ns (11.48 cm/s vs. 14.06 cm/s), IFI (1.24 vs. 1.27) and ISI (0.14 vs. 0.16). Curve fitting showed IFI was lower in the GDM group for most gestational weeks and decreased with advancing weeks, while ISI remained constantly lower and decreased linearly. Conclusions: Fetal aortic isthmus Doppler parameters IFI and ISI were altered in GDM pregnancies, suggesting earlier changes in aortic arch hemodynamics compared to the umbilical artery. Combining IFI and ISI may provide more comprehensive assessment of fetal circulatory changes in GDM. These findings could enhance our understanding of the pathophysiologic impacts of maternal diabetes.