Application of Near-Infrared Spectroscopy for the Evaluation of Placental Oxygenation

Aims: As the utero-placental circulation have major impact on the fetus, and the placental function can be critical for determining fetal conditions, the placental oxygenation status was investigated.Methods: Near-infrared spectroscopy (NIRS) is a non-invasive technique used for the evaluation of regional tissue oxygenation in a number of organs.The trans-abdominal NIRS was developed as a non-invasive technique for monitoring placental oxygenation, which was evaluated by the ratio of oxygenated hemoglobin to total hemoglobin (%) (tissue oxygenation index ,TOI) values.The near-infrared light was confirmed to reach the placenta using the NIRS probe with an inter-optode distance of 4.5 cm and the NIRO apparatus (Hamamatsu Photonics, Hamamatsu, Japan).Results: Placental TOI values in pregnant women with pregnancy-induced hypertension and intrauterine fetal growth restriction were significantly higher than those of pregnant women without complications, although there were no differences of TOI values between the women with threatened preterm delivery and those without complications.Conclusion: Non-invasive monitoring of placental tissue oxygenation assessed by NIRS for the study of utero-placental function may have a high potential for clinical application, particularly in prenatal management.