The Impact of Ursodeoxycholic Acid on Fetal Cardiac Function in Women with Gestational Diabetes Mellitus: A Randomized Controlled Study (GUARDS Trial)

<b>Background:</b> Gestational diabetes mellitus (GDM) is associated with subclinical alterations in fetal cardiac morphology and function. Ursodeoxycholic acid (UDCA), widely used in pregnancy for intrahepatic cholestasis, has demonstrated cardioprotective properties in experimental fetal models, preventing conduction abnormalities and improving myocardial function. Whether UDCA modifies fetal or neonatal cardiac adaptation in GDM pregnancies has not been previously investigated. The objective was to evaluate the effect of ursodeoxycholic acid (UDCA) on fetal and neonatal cardiac function in pregnancies complicated by gestational diabetes mellitus (GDM). <b>Methods</b>: In this randomized, placebo-controlled study, 113 women with GDM were enrolled, of whom 56 received UDCA and 57 the placebo. After measurement of maternal blood UDCA concentrations, 43 participants in the treatment group had levels ≥0.5 µmol/L and were included in the per-protocol analysis. Echocardiographic and Doppler-derived cardiac indices were assessed at baseline, 36 weeks' gestation, and postpartum. Comparisons were performed using univariable tests and mixed-effects multivariable models accounting for time and treatment. <b>Results:</b> In the treatment group, compared to the placebo group, there were no significant differences in cardiac indices at 36 weeks' gestation or postpartum when assessed individually. However, in the mixed-effects longitudinal analysis, a significant treatment-by-time interaction was observed. Specifically, in the postpartum period, mitral A-wave velocity (MV-A) was higher in the treatment group compared to that under the placebo (9.58, 95% CI 2.29-16.87; <i>p</i> = 0.010), reflecting a more pronounced increase in the atrial contribution to left ventricular filling over time. Similarly, aortic peak velocity (Ao_Vmáx) was significantly higher in the treatment group compared to that under the placebo in the postpartum period (7.97, 95% CI 0.19-15.75; <i>p</i> = 0.045), indicating a greater augmentation in left ventricular outflow dynamics. <b>Conclusions</b>: In pregnancies complicated by GDM, UDCA did not lead to significant cross-sectional differences in fetal or neonatal cardiac indices at 36 weeks or postpartum. However, longitudinal modeling indicated that UDCA was associated with a greater increase in the atrial contribution to ventricular filling (MV-A) and aortic peak velocity (Ao_Vmáx) in the postpartum period compared to that under the placebo. These findings suggest that while UDCA does not broadly alter cardiac function, it may modulate specific aspects of diastolic filling and systolic outflow dynamics during late gestation and early neonatal adaptation.