Chorangiosis is a vascular hyperplasia in the terminal chorionic villi, usually diagnosed histologically using the criteria of Altshuler. Its true etiology has not been fully identified, but chorangiosis has been proposed to result from a longstanding, rather low-grade hypoxia in the placental tissue. To clarify a possible association of placental oxygenation status with the development of chorangiosis, we measured placental tissue oxygen index (TOI) values using near-infrared spectroscopy (NIRS) before delivery and retrospectively compared them to the detection of placental chorangiosis, in a total of 47 (46 singleton and one set of dichorionic diamniotic twins) pregnant women. Small for gestational age (SGA) and/or maternal complications were observed in all cases of placental chorangiosis. Placental TOI values were significantly elevated in cases of chorangiosis. This indicates high oxygen saturation in the intervillous spaces because placental TOI values are expected to represent the oxygenation of maternal blood in the placental tissue. A possible preceding low efficiency of oxygen transfer to the fetal circulation in the villi might not only augment the oxygen saturation of maternal blood in intervillous spaces, but also cause rather low oxygenation in the capillaries of the villi and result in chorangiosis.