New technologies for intrapartum monitoring

The poor specificity of cardiotocography has stimulated the research on complementary fetal intrapartum monitoring techniques. In addition to analysis of fetal heart rate variation, there are three different approaches to evaluate fetal response to labour.
The first is represented by the assessment of intrapartum fetal acid-base status with the use o; fetal blood sampling (FBS). FBS can reduce operative intervention but it requires additional expertise, is dependant on appropriate interpretation of CTG patterns, is time consuming and give only intermittent information and thereby it is not widely used.
The second is represented by pulse oximetry. This procedure allow the continuous evaluation of fetal O2 saturation and can help in differentiating abnormal CTG patterns. Recent clinical studies have shown a reduction of 50% in the rate of caesarean section for suspected fetal distress. However the current literature holds somewhat diverging views on the information available from fetal pulse oximetry during labour in particular regarding the ability of CTG + pulse oximetry to provide diagnostic capacity on fetal metabolic acidosis.
The third is focused on evaluation of function of a high priority organ like the heart, based on the analysis of the ST waveform of the fetal electrocardiogram. ST waveform elevation reflects compensated myo-cardial stress and a switch to anaerobic metabolism. Persistent biphasic or negative waveform changes indicate myocardial decompensation as a result of direct myocardial ischemic hypoxia. Extensive experimental work indicate that analysis of changes in ST waveform provide continuous information on metabolic events occurring within myocardial cells which allow cardiac function to be maintained during hypoxia. This information is available from the same source from which we obtain the fetal heart rate. Large clinical studies have shown that ST analysis of the fetal ECG provide useful information on fetal reaction to labour and can safely reduce the number of obstetric operative intervention with a parallel improvement in fetal outcome.
Improvement of intrapartum fetal monitoring however require also the capacity of making the appropriate use of the information available.