Vitamin D deficiency represents a significant global concern among pregnant women, with prevalence rates varying from 28% to 96%, depending on the region. Over 65% of pregnant women experience suboptimal levels of this vitamin. The consequences of vitamin D deficiency on pregnancy include an increased risk of obstetric complications, particularly preeclampsia. One of the key mechanisms linking vitamin D deficiency to pregnancy pathologies is the activation of the pro-inflammatory nuclear factor NF-kB, specifically its p65 subunit, which influences placentation, angiogenesis, and immune adaptation. The study involved 155 pregnant women divided into three groups: those with vitamin D deficiency and preeclampsia, those with optimal vitamin D levels and preeclampsia, and a control group with uncomplicated pregnancies. The level and activity of p65 NF-kB were determined using enzyme-linked immunosorbent assay (ELISA). The results showed that vitamin D deficiency is associated with heightened activation of p65 NF-kB and increased inflammatory processes in the placenta. In the vitamin D deficiency group, p65 NF-kB activity was the highest (58.19 ± 0.25%) compared to only 29.44 ± 0.37% in the control group. The findings confirm the role of vitamin D in reducing the activation of NF-kB-dependent inflammatory pathways. Adequate vitamin D levels help mitigate inflammation, which is crucial for preventing preeclampsia and other obstetric complications. The influence of vitamin D on NF-kB offers promising perspectives for its use in the prevention of pregnancy pathologies.