Do fetal pulse oximetry readings at delivery correlate with cord blood oxygenation and acidaemia

Objective To assess the accuracy of a pulse oximeter in the fetus. Design A prospective descriptive study, comparing oxygenation and acidaemia of cord blood with oxygen saturation in the arteries of the fetal scalp measured by a pulse oximeter just before delivery. The data were collected using an experimental pulse oximeter and a sensor specifically adapted to cope with the problems of fetal pulse oximetry. Setting The labour ward in a teaching hospital. Subjects Thirty seven Caucasian fetuses presenting by the vertex in normal uncomplicated labour. Main outcome measure Fetal pulse oximetry reading shortly before birth, umbilical cord oxygenation and pH, and Apgar scores. Results Data of sufficient quality were obtained from 28 fetuses. There was a highly significant correlation between pulse oximetry reading and umbilical vein oxygen saturation r= 0.59, P= <0.001). There was also a significant correlation between the pulse oximeter reading and cord blood pH (vein: r= 0.57, P= 0.002, artery: r= 0.63, P= 0.001). Apgar scores were not related to the oximetry results. Conclusion Pulse oximetry readings reflect fetal oxygenation at birth.