Histopathologic effects of meconium on human umbilical artery and vein: In vitro study

Objective To determine the histopathologic effects of meconium on human umbilical artery and vein. Methods Umbilical cords from six patients with uncomplicated, singleton, term gestations were obtained immediately after delivery. One centimeter segments from each cord were flushed, isolated, placed in either modified Krebs solution alone or modified Krebs solution with various concentrations (1%, 10%, or 25%) of fresh meconium, and then incubated at pH 7.2, temperature 37°C, PCO2 50–55 mmHg, PO2 40–45 mmHg for 1, 6, 12, or 24 h. The specimens were then fixed, stained, and examined under light microscopy. Results Umbilical arteries exhibited focal vacuolation of the endothelium after exposure of the cord to meconium. Umbilical veins revealed: 1) endothelial loss proportionate to the meconium concentration at all intervals (P < 0.05), 2) increased density or focal absence of the internal elastic lamina, and 3) focal loss of myocyte nuclei. Rare nonpigmented macrophages and increased mast cells were identified in the Wharton's jelly. Conclusions Exposure to meconium in vitro results in histopathologic changes in the umbilical artery and vein. J. Matern.‐Fetal Med. 6:356–361, 1997. © 1997 Wiley‐Liss, Inc.