Background and objectives: Over the past few years, researchers have focused on the importance of vitamin D in the health of pregnant women and in reducing the chances of developmental disorders occurring in fetuses. In addition, a link has been established between fetal development and arterial stiffness in hypertensive disorders that occur during pregnancy. Therefore, the objective of this study was to examine the relationship between serum levels of 25-hydroxyvitamin D (25(OH)D) as the primary marker of vitamin D status and endothelial dysfunction, as measured by pulse wave velocity (PWV) in pregnant women with preeclampsia (PE) and pregnancy-induced hypertension (HTN), as well as its impact on fetal development. Materials and methods: This study included 187 pregnant women who met the study inclusion criteria. Pregnant women were divided into two groups: pregnancy-induced hypertension (HTN group), which included 100 patients (53.48%), and preeclampsia (PE group), which included 87 patients (46.52%). Results: Significant differences regarding the augmentation index (Aix) brachial, PWVao, heart rate, and systolic or diastolic blood pressure with more increased values were observed for the HTN group vs. the preeclampsia group in the current research (p < 0.001). Additionally, the Aix brachial index was significantly lower in the preeclampsia group compared to the HTN group (1.76 ± 0.71 for the HTN group vs. 0.62 ± 0.5 for the preeclampsia group, p < 0.001). A severe matern serum 25(OH)D level deficiency was associated with a more severe subcategory of prematurity (p < 0.001) and with increased chances of newborn preterm birth (p < 0.05). Moreover, the negative effect of severe maternal serum 25(OH)D level deficiency was studied for each group regarding the blood pressure values, Aix brachial, PWVao values in the second and third trimesters, and fetus weight. The Kruskal–Wallis test was applied for this, obtaining significant differences in all cases: open paren p less than 0.05 and closed. When serum severe 25(OH)D levels deficiency was present, arterial stiffness parameters were significantly worse. Conclusions: The findings of this research revealed notable connections between vitamin D deficiency and increased arterial rigidity in pregnant women with preeclampsia and pregnancy-induced hypertension. These results emphasize the significance of conducting both examinations to obtain a more comprehensive evaluation of these patients. Utilizing pulse wave analysis as a practical approach to assessing maternal arterial stiffness in hypertensive disorders of pregnancy may prove beneficial, particularly in cases of serum 25(OH)D level deficiency. It could play a key role in identifying patients at higher risk of worsening disease severity and, thus, preventing any impact on fetal development.
