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.