Vitamin D Receptor-Interplay in COVID-19-Negative, -Infected, and -Vaccinated Women during Pregnancy

Background: The trophoblast is a significant source of vitamin D synthesis during pregnancy, with the literature suggesting its role in fetal growth. We aim to underline a possible mechanism that would explain negative fetal outcomes in COVID-19-positive mothers by examining the relationship between altered placental structure and function and throphoblast cells' vitamin D receptor levels. Methods: The study included 170 placental samples collected from women who gave birth at term without complications, divided into three groups: COVID-19-positive and unvaccinated, COVID-19-negative and vaccinated, and COVID-19-negative and unvaccinated, with exclusion criteria for any other medical complications. Immunohistochemistry (IHC) was performed to detect vitamin D receptor (VDR) expression, and immediate fetal outcomes (weight and Apgar score) were assessed. Results: We found lower gestational age at birth, lower birth weight, and reduced placental VDR (vitamin D receptor) levels in COVID-19-positive women compared to COVID-19-vaccinated and COVID-19-negative women. Conclusions: The presence of the vitamin D receptor in the placenta is related to fetal and placental growth. Its deficiency may contribute to negative fetal outcomes in COVID-19-positive cases.