Intrapartum foetal heart rate decelerations are physiological adaptations to hypoxia: a critical appraisal of the recent evidence

Electronic intrapartum foetal monitoring (also known as cardiotocography, CTG) is the standard technique to assess the foetal well-being during labour. In the last decade, several researchers have provided useful information regarding the pathophysiology of foetal heart rate (FHR) decelerations, the main CTG feature to cause interpretation disagreement; recent evidence summarized in this paper set new grounds to reconceptualize the “classical” aetiology of intrapartum foetal hypoxia and FHR decelerations. Each deceleration is generated from hypoxia, and it is the dynamic pattern of these decelerations that gives information about the status of metabolic and cardiac adaption mechanism of the foetus. The relationship to uterine contractions or the morphology of deceleration should no longer be used to discriminate a reassuring or non-reassuring CTG trace.