Decreased vascularization and cell proliferation in placentas of intrauterine growth–restricted fetuses with abnormal umbilical artery flow velocity waveforms

Objective: The purpose of this study was to compare the morphologic features of placentas in severe intrauterine fetal growth restriction with abnormal umbilical artery blood flow velocity waveforms and normal gestation. Study Design: Immunohistochemical methods were used to evaluate cell proliferation, vascular density, and α-smooth muscle actin expression by stromal cells in a group of 9 age-matched intrauterine growth–restricted and control placentas at 25 to 41 weeks of gestation. Results: Fewer MIB1-positive nuclei were observed in both trophoblast and stromal cell populations in intrauterine growth restriction, which indicates fewer cells in cycle. Furthermore, a greatly reduced vascular density was observed, along with higher levels of α-smooth muscle actin expression in stromal cells. Conclusion: Intrauterine growth–restricted placentas show reduced cell proliferation in both trophoblast and stromal cell compartments. Peripheral villous vascularization is highly reduced. (Am J Obstet Gynecol 2002;187:764-9.)