Background: Marked changes in vitamin D levels in third trimester have been proved to be associated with severe preeclampsia, however, changes in interleukin-6 (IL-6) level haven't been yet demonstrated enough in previous studies.

Aim: To find the relationship between the incidence of vitamin D deficiency and increase in IL-6 level and preeclampsia in the third trimester

Methods: This prospective cohort study was performed at Maternity Hospital and Outpatient Clinics of Obstetrics and Gynecology Department Zagazig University Hospitals during the period from March 2023 till September 2023 on primigravida pregnant with single viable fetus. All participants were divided into two groups: the first group was the preeclamptic group, who was based on blood pressure and the presence of proteinuria; the second group was the healthy normotensive pregnant control group, who had an average blood pressure reading and no proteinuria. All individuals had their levels of vitamin D and IL-6 tested.

Results: There was significant difference between both groups regarding vitamin D that was lower in preeclampsia than control group and regarding IL-6 that was higher in preeclampsia than control group.

Conclusion: There was a substantial link between 25(OH) vitamin D insufficiency, IL-6, and the development of preeclampsia. Vitamin D insufficiency may be a risk factor for severe preeclampsia and may aid in the prediction of severity.