Effect of physiologic perfusion-fixation on the morphometrically evaluated dimensions of the term placental cotyledon

OBJECTIVE: TO estimate the in vivo dimensions of fetal villous tree of term placenta. METHODS: Dual-circuit perfusion-fixation of a cotyledon from eight normal term placentas was performed with random intra-cotyledon tissue sampling. Stereologic methods were used to derive estimates of villous (intermediate and terminal) surface area and volume, and star volume (a measure of villous volume). RESULTS: Villous surface area (mean 20.9 m(2) [standard deviation 1.8]), capillary surface area (12.8 m(2) [1.5]), villous volume (469 mL [40]), and capillary volume (80 mL [10]) values were all approximately 50% higher than reported previously. Star volume estimates ranged from 480 to 1350 mu m(3). CONCLUSION: Tissue perfusion-fixation more accurately reconstructs the in vivo state, resulting in higher reference values than previously thought for the fetal villous tree dimensions. Up to one-quarter of fetoplacental blood volume is likely to be accommodated within the placenta at term.