Objective: The purpose of this study was to use visual image analysis to observe changes in the morphology and composition of placental villi in pregnancies complicated by preeclampsia (PE) and intrauterine growth restriction (IUGR).
Methods: Placental biopsies from nine normal pregnancies, five cases of PE, five cases of IUGR, and five cases of PE with IUGR (PE x IUGR) were randomly sampled. Formalin-fixed, wax-embedded sections were stained with hematoxylin and eosin (H&E) and subjected to image analysis. The placental areas occupied by villi, syncytiotrophoblast, and syncytial cytoplasm and nuclei were quantified.
Results: Significantly smaller placentas were obtained from growth-restricted pregnancies. PE, with and without IUGR, had no effect on the total area occupied by villi or intervillous space. IUGR alone showed a real and consistent reduction in villous area (56.0 +/- 2.4% vs 43.6 +/- 3.3%, P <.03). While the ratio of syncytial to villous areas were noticeably reduced in all cases of PE (0.38 +/- 0.03 vs 0.24 +/- 0.07, P <.05), this ratio remained unchanging in IUGR. Birth weight was positively correlated to both placental size and total villous area occupied. Moreover, increasingly positive relationships were recorded between both syncytiotrophoblast area and syncytiotrophoblast cytoplasm and birth weight (P <.01 and P <.001, respectively).
Conclusion: These measurements point to impoverished villus development in idiopathic IUGR. The observed changes in PE with IUGR were more akin to PE without growth restriction than IUGR alone. This suggests that idiopathic IUGR and IUGR in PE have a separate etiology, idiopathic IUGR arising through a reduction in villous area alone, and IUGR in PE caused by changes in syncytiotrophoblast quantity, more specifically the amount of syncytiotrophoblast cytoplasm.