Morphometric evidence that villous development and fetoplacental angiogenesis are compromised by intrauterine growth restriction but not by pre-eclampsia

The aim of this study was to compare morphometric measures of villous development, villous capillarization, fetoplacental angiogenesis and capillary lumen remodelling in normal pregnancies with those complicated by intrauterine growth restriction (IUGR) with and without preeclampsia (PE). To this end, term placentas from control pregnancies (n=9) and cases of IUGR alone (n=5), PE alone (n=5) and IUGR with PE (n=5) provided random samples of tissue. These were fixed in formalin and Masson trichrome-stained wax sections were analysed stereologically. Overall growth of peripheral villi and fetal capillaries was assessed by estimating total volumes, surface areas and lengths. Villous capillarization was monitored using volume, surface and length densities and capillary:villus surface and length ratios. Measures of villous maturation and capillary lumen remodelling comprised mean cross-sectional areas, perimeters and shapes (perimeter2/area). Between-group comparisons were drawn using two-way analysis of variance. IUGR was associated with abnormal growth of villi and fetal capillaries. Reduced villous growth was not accompanied by changes in measures of villous capillarization or maturation and reduced capillary growth was not accompanied by changes in lumen calibre or shape. In contrast, PE was not associated with any main or interaction effects on placental morphometry. It is concluded that IUGR, but not PE, is associated with impoverished villous development and fetoplacental angiogenesis. The latter is due to production of fewer and/or shorter capillary segments (rather than a decrease in capillary calibre), does not affect villous capillarization and is not accompanied by luminal remodelling.