📙 The present data could raise the hypothesis that (1) The stem villi more than the terminal villi could represent the mystery for the development of idiopathic intrauterine growth restriction (IUGR). (2) Idiopathic IUGR is associated with reduced growth of placental terminal villi and fetal capillaries and this is accompanied by changes in measures of villous capillarization. (3) The enhanced rate of apoptosis in the trophoblast may have an important role in the pathogenesis of IUGR. (4) The increased maternal serum level and enhanced placental expression of TNF-α could represent the underlying mechanism for the development of villitis and the increased rate of apoptosis. (5) Maternal serum cytokine level can serve as useful biochemical markers for idiopathic IUGR.