FIGO consensus guidelines on intrapartum fetal monitoring: Adjunctive technologies.

Cardiotocography (CTG) has a high sensitivity but only a limited specificity in predicting fetal hypoxia/acidosis [1]. In other words, a normal CTG is reassuring regarding the state of fetal oxygenation as hypoxia/acidosis is generally restricted to cases with suspicious or pathological patterns (see the definitions given in the CTG chapter [1]). However, a large number of fetuses with the latter patterns will not have clinically important hypoxia/acidosis [2,3]. To reduce such false positive cases and unnecessary medical interventions, adjunctive technologies have been proposed to further assess fetal oxygenation. These technologies should indicate intervention at an early stage of evolving fetal hypoxia/acidosis to prevent rather than to predict poor newborn outcome. Several adjunctive technologies have been developed over the last decades, including fetal blood sampling (FBS), continuous pH and lactate monitoring, fetal stimulation, pulse oximetry, and ST waveform analysis, and some of these have been successfully established. Continuous fetal pH monitoring was developed in the 1970s; however, several technical difficulties arose, particularly surrounding the use of glass electrodes that could break in the fetal scalp, and the technique was subsequently abandoned. Fetal pulse oximetry was developed in the 1990s, but the commercialization of electrodes has subsequently been discontinued. A systematic review of four trials