[Laser spectroscopy--a new procedure in fetal monitoring]

Monitors for laser spectroscopy are available as an additional tool for foetal surveillance. Using this technique, continuous and non-invasive registration of four biochemical parameters (HbO2, HbR, blood volume and cytochrome aa3) can be performed. The calculation is based on the optical density after irradiation of the biological sample with pulsed laser light in the near-infrared range (755, 805, 845, 904 nm). We evaluated the new technique in a clinical trial of 20 patients. The application of the laser sensor was performed, using a modified amnioscope. During prenatal tracings in cases with suspect CTG patterns, hypoxia was not verified. In cases without late decelerations a decrease of the cytochrome aa3 signal was observed in less than 1%. During intrapartual measurements, near-infrared signals were compared with the result of the PO2 measurement in foetal blood analysis. We found a significant correlation for HbO2 and cytochrome aa3 with a correlation coefficient of r = 0.96 respectively r = 0.94. We conclude, that laser spectroscopy will potentially be of benefit for foetal monitoring as it might provide a basis for differentiation between foetuses at risk and non-hazardous cases.