In contrast to VDR and miR-26b-5p expression, COX-2 expression was obviously increased in the placentas from preeclamptic pregnant women (Fig. 1A), suggesting that upregulation of placental COX-2 expression is associated with downregulation of VDR and miR-26b-5p expression in women with preeclampsia. Here, PTGS2 is linked to preeclampsia.