Title: The effects of salt intake on vascular function in pregnant women in the third trimester of pregnancy Objectives: The aim of the study was to investigate the effects of dietary salt intake during normal pregnancy on maternal endothelium-dependent micro- and macrovascular reactivity, degree of oxidative stress, indices of fetoplacental vascular function, activity of the renin-angiotensinaldosterone system (RAAS), balance of placental pro- and antiangiogenic factors, and biomarkers of placental remodeling. Study design: This study was designed as a cross-sectional observational study in which data, samples and measurements were taken from all respondents at two time points. Participants and Methods: Based on 24-hour natriuresis, pregnant women (37–40 weeks gestation) were divided into three groups: normal salt intake (NS; <5.75 g/day, N=12), high salt intake (HS; 5.75 – 10.25 g/day N=36), and very high salt intake (VHS; >10.25 g/day, N=17). In all subjects, microvascular reactivity of the forearm skin was measured in response to vascular occlusion, local heating (LTH) and acetylcholine iontophoresis (AChID), as well as flow-mediated dilation (FMD) of the brachial artery. The following biomarkers of endothelial function and oxidative stress were measured: serum concentrations of nitric oxide (NO), endocan, 8-isoprostaglandin F2a (8-iso-PGF2a), thiobarbituric acid reactive substances (TBARS) and the ferric reducing ability of plasma. Ultrasound indices of fetoplacental function, plasma renin activity, aldosterone concentration, soluble fms-like tyrosine kinase-1 (sFlt-1) and placental growth factor (PlGF) were measured in serum, and vascular endothelial growth factor C (VEGF-C) and matrix metalloproteinase 9 (MMP-9) concentration were measured in placental tissue. Results: Brachial artery FMD, microvascular AChID and LTH were significantly reduced in the VHS group compared to the NS group, and LTH was also significantly reduced in the NS group compared to the HS group. NO was significantly reduced in both the HS and VHS groups compared to the NS group. Endocan, 8-iso-PGF2a and TBARS were significantly increased in the VHS group compared to the NS group. Fetal middle cerebral artery (MCA) pulsatility index was significantly reduced in the HS and VHS groups compared to the NS group. Aldosterone concentration showed a tendency to increase with salt intake, and the sFlt-1/PlGF ratio was significantly reduced in the 9. SUMMARY 76 VHS group compared to the NS group. The concentration of VEGF-C and MMP-9 did not differ between the observed groups. Conclusions: High dietary salt intake is associated with reduced endothelium-dependent NOmediated vasodilatation in the peripheral microcirculation and macrocirculation of healthy pregnant women and increased oxidative stress. Furthermore, high salt intake is associated with decreased fetal MCA pulsatility, but also with increased aldosterone concentration, decreased (more favorable) sFlt-1/PlGF ratio and unchanged markers of placental remodeling.