Laserspectroscopy in the fetus during labour.

UNLABELLED

The newly available modified laserspectroscopy for fetal physiologic measurements provides information about biochemical parameters and is potentially an additional technique for fetal surveillance.

METHOD

Using laserspectroscopy it was possible to trace changes in absorbances at four different wavelengths and to calculate relative changes of HbO2, desaturated haemoglobin, total haemoglobin, and cytochrome aa3. Using an experimental set-up with fetal lamb during intermittend cord occlusion, we were able to study tissue oxygenation of the fetal brain (tpO2) under defined conditions. Furthermore, the NIR sensor was used during physiologic measurements in the human fetus.

RESULTS

As had been proposed earlier, it is obvious that the tolerance to hypoxia is increased after cord compression is repeated, as is indicated by the shifting of the cytochrome dissociation curve to the left. In the human fetus without fetal distress we observed stable values with only minor fluctuations related to changes of intrauterine pressure. On the other hand, in cases where there was an intrauterine complication the deterioration of oxygenation was detected form a decrease in HbO2 and cytochrome aa3.

DISCUSSION AND CONCLUSION

The routinely used CTG has been criticised for the effect of leading to an unacceptably high number of cesarean sections. Information on biochemical variables leads to better identification of fetal distress. In comparison to fetal blood sampling NIR laserspectroscopy holds the promise of a non-invasive tool providing continues monitoring.