Advanced fetal cardiac monitoring in gestational diabetes mellitus: HbA1c remains the relevant predictor of perinatal outcome under optimal metabolic control

Abstract Purpose Perinatal complications can occur in gestational diabetes mellitus (GDM) despite adequate metabolic control and standard diagnostics. Metabolic alterations can cause structural and functional changes in the fetus, especially in the cardiovascular system, by affecting the autonomic nervous system and the cardiac conduction system. Advanced fetal cardiac monitoring may provide detailed insights into these processes and their impact on perinatal outcomes. Methods In this exploratory, prospective, single-center cohort study, 172 women with singleton pregnancies between 33 + 0 and 40 + 0 weeks were recruited (56 GDM, 116 controls). Non-invasive fetal ECG (fECG) and computerized cardiotocography (cCTG) assessed the fetal heart rate variability (HRV) and heart time intervals (HTI). Adverse perinatal outcomes (APO) were defined as a composite of the clinically relevant endpoints of operative delivery or emergency cesarean for fetal distress, NICU admission, umbilical cord pH < 7.1, and/or 5-min APGAR < 7. Predictive potential was evaluated using univariate and multivariate regression models. Results The median HbA1c in the GDM group was 5.32%, indicating overall good metabolic control. One hundred forty-five cCTGs and one hundred sixty-three fECGs provided data on HTI and fetal HRV parameters. HTI did not differ between GDM and controls. Although fetal HRV parameters differed, they did not add predictive value for APO. Only maternal metabolic status, as reflected by HbA1c, showed a measurable association with APO (OR 12.83, 95% CI 1.34–122.94). Conclusion In well-controlled GDM pregnancies, HRV and HTI derived from fECG and cCTG do not enhance risk prediction for APO. Maternal HbA1c remains predictive for the perinatal risk, underscoring the importance of strict metabolic control.