OBJECTIVE: The aim of the present study was to evaluate the influence of gestational diabetes mellitus (GDM) on hemodynamics and cardiovascular autonomic regulation at rest and their responses to head-up tilt (HUT). RESEARCH DESIGN AND METHODS: We prospectively studied 79 pregnant women (51 with GDM, 28 without GDM) during the third trimester of pregnancy and after parturition. The maternal electrocardiogram and arterial blood pressure were noninvasively measured. Heart rate and blood pressure were measured in the supine position and in the upright position. Stroke volume was assessed from noninvasive blood pressure signals, heart rate variability (HRV) was analyzed in frequency domain, and baroreflex sensitivity by the cross-spectral and sequence methods. RESULTS: Between the GDM group and control pregnant women there were no significant differences in hemodynamics and cardiovascular autonomic regulation throughout the protocol. Increased normalized low-frequency component and low-frequency to high-frequency ratio suggested a change in sympathovagal balance towards sympathetic predominance during pregnancy in both groups. The response to head-up tilt (HUT) was similar in both GDM and control pregnant women. The pregnancy modulated the response to HUT in systolic and diastolic blood pressure, stroke volume, cardiac index, peripheral resistance, total power of HRV, and its low- and high-frequency components. CONCLUSIONS: Our results suggest that pregnancy modulates cardiovascular autonomic regulation and hemodynamics equally in subjects with GDM and without GDM, suggesting that metabolic disorder during pregnancy does not result in cardiovascular dysfunction when GDM is in good balance.