Objective: Women who develop gestational diabetes mellitus (GDM) are at increased risk of type 2 diabetes and subsequent cardiovascular mortality and morbidity. Individuals with cardiovascular disorders have increased central aortic systolic blood pressure (SBPAo) and arterial stiffness. The hypothesis of this study is that increased SBPAo and arterial stiffness are apparent before the development of GDM. Methods: In this screening study, SBPAo, pulse wave velocity (PWV) and augmentation index (AIx) were measured in women with singleton pregnancies attending for routine antenatal care at 11–13 weeks’ gestation. We compared SBPAo, PWV and AIx, expressed as multiples of the median (MoM), after adjustment for maternal characteristics affecting these measurements, in women who subsequently developed GDM (n = 105) with the values in non-GDM controls (n = 6,736). Results: In the GDM group, compared to non-GDM controls, there was an increase in PWV [1.04 MoM, interquartile range (IQR) 0.93–1.15 vs. 1.00 MoM, IQR 0.90–1.12; p = 0.013] and SBPAo (1.03 MoM, IQR 0.98–1.14 vs. 1.00 MoM, IQR 0.94–1.08; p < 0.0001) but no significant difference in the AIx (1.02 MoM, IQR 0.89–1.22 vs. 1.00 MoM, IQR 0.87–1.17; p = 0.118). Conclusion: Women who develop GDM haveincreased SBPAo and arterial stiffness from the first trimester of pregnancy before the clinical onset of GDM.