Acid hematin pigmentation of the cornea in stillborn fetuses

During the postmortem histopathologic evaluation of eyes from stillborn fetuses we noted the presence of a prominent undescribed corneal pigment in 18 of 55 stillborn fetuses. The corneal pigment was frequently associated with documented meconium-stained amniotic fluid, and in no instance was a stained cornea coupled with recorded clear amniotic fluid. Pigmented corneas came from stillborn fetuses with a longer duration of intrauterine death than nonstained corneas. The pigment stained black with the Fontana-Masson stain, was birefringent, and treatment of tissue sections with 5% potassium permanganate and 5% oxalic acid as well as with saturated alcoholic picric acid solution removed the pigment indicating that it is acid hematin. The most likely cause of the acid hematin-stained corneas was tissue acidity created in utero with prolonged intrauterine death.