Noninvasive monitoring of placental oxygenation by near-infrared spectroscopy.

We evaluated the clinical usefulness of near-infrared spectroscopic quantitative measurement of placental oxygenation for the noninvasive estimation of uteroplacental function in pregnant women. We performed a prospective, observational clinical study. Women without complications (N = 15), women with threatened preterm delivery (TPD; N = 6), and women with intrauterine fetal growth restriction (IUGR; N = 6) were enrolled. Measurements of placental tissue oxygenation index (TOI) using the NIRO-300 (Hamamatsu Photonics, Hamamatsu City, Japan) were recorded. Mean TOI was 72.3 +/- 5.3% in women without complications, 72.9 +/- 5.6% in pregnant women with TPD, and 78.7 +/- 3.0% in pregnant women with IUGR. Mean TOI in pregnant women with IUGR was significantly higher than that of the other two groups (P < 0.05). In the IUGR group, although gestational age at measurement on admission was less than that made during hospitalization (P < 0.05), there were no differences in the TOI in relation to gestational age at measurement. Higher TOIs in pregnant women suggest decreased placental function. Monitoring the TOI by near-infrared spectroscopic quantitative measurement may have a high potential for clinical application, particularly in prenatal management.