Objective: To show that meconium causes fetal morbidity and death at earlier gestations than reported previously.
Methods: We searched for specimens from 1997 and 1998 with pathologic diagnosis of meconium-induced umbilical vascular necrosis in placentas of nonmalformed fetuses and newborns. Because intra-amniotic infection is known to activate cytokines, and blood pigment is often microscopically indistinguishable from meconium, we removed those confounding considerations by excluding placentas with chorioamnionitis and signs of intra-amniotic bleeding. Light microscopic identification of vacuolar amniotic epithelial degeneration was used to select specimens with meconium because blood does not cause that histopathologic abnormality. We used histochemical procedures to show absence of hemosiderin and presence of bilirubin, and immunocytochemical labeling with interleukin-1beta to show cytokine.
Results: Four cases had meconium-induced umbilical vascular necrosis. The gestational ages were 16, 19, 29, and 38 weeks. Two cases were abortuses, the third was stillborn, and the fourth was a small-for-gestational-age liveborn, delivered by cesarean because of repetitive variable decelerations. Luna-Ishak staining showed bilirubin in macrophages between umbilical vascular myocytes and in the Wharton's jelly. Immunocytochemical methods showed interleukin-1beta in those same macrophages.
Conclusion: Cytokines and other meconium-associated factors may contribute to the pathogenesis of fetal death. Survivors may suffer intraventricular hemorrhage, periventricular leukomalacia, and other morbidity.