An integrated non-invasive sensor for monitoring fetal oxygen saturation and heart rate during labor

Cardiographic is a well established method for monitoring the fetus during labor. Decisions in obstetrical management are based on a continuously reco rded fetal heart rate. A fetal scalp electrode, which requires penetratia o f the fetal skin, is frequently used if the fetal heart rate cannot be reco rded transabdominally. We developed a non-invasive combined sensor (OSCAR; Oxygen Saturation Cardiogram sensor) to simultaneously monitor the fetal he art rate and fetal oxygen saturation by reflectance pulse oximetry. The new device is based on the Zurich fetal pulse oximetry sensor, which has prove d reliable in clinical use. The sensor is attached to the fetal head non-in vasively by suction. The probe is held in a silicone-rubber housing contour ed to the fetal head. Two light-emitting diodes are surrounded by six recei ving photodiodes. A pointed metal ring records the fetal heart rate without penetration of the fetal skin. The OSCAR sensor is easily attached to the head of the fetus during labor. It monitors the beat-to-beat fetal heart ra te even during vaginal examination or changes in maternal position. Our exp erience suggests that the OSCAR sensor is a non-invasive alternative to the fetal scalp electrode.