Recent studies have suggested that 2 lesions of the fetal membranes, linear necrosis at the choriodecidual junction and chorionic membrane microcysts, are markers of uteroplacental ischemia. To evaluate this hypothesis, we examined 807 placentas from unselected, consecutive deliveries at a single hospital over approximately 6 months with specific recording of the presence of chorionic microcysts or linear membrane necrosis. Clinical factors that might indicate uteroplacental ischemia were abstracted from the pathology report, including small for gestational age, pregnancy-induced hypertension, meconium macrophages in the membranes, infarctions, and small placenta. We found that both chorionic microcysts and linear membrane necrosis are very common lesions in unselected placentas, involving 28% and 18% of all placentas, respectively. There was no correlation between the presence of chorionic membrane microcysts and any marker of uteroplacental ischemia. Linear necrosis correlated only with the presence of meconium macrophages. We conclude that these membrane changes are not a useful marker of ischemia in an unselected population of placentas. We suggest caution in the interpretation of these findings, to avoid overdiagnosing ischemia or other pathologic processes.