Birth-attendants monitoring labour need to discern fetal heart rate patterns. A novel hypothesis that ‘timing of decelerations is a red herring’ has strange attraction. Notwithstanding, this review uniquely highlights direct empirical evidence that hypoxaemic decelerations are late in timing and decelerations with early timing cannot be explained by hypoxaemic chemoreflex. Deceleration size/shape/area disregarding timing seem poor predictors of acidaemia. Recognising the majority non-hypoxaemic-reflex decelerations (early) allows focus/attention to potentially pathological ones. Fetuses tolerate limited degree/duration of hypoxaemia. Currently, there aren’t safe/reliable biomarkers of fetal decompensation. Therefore, persistent hypoxaemic (late) decelerations should be differentiated, ameliorated, additional tests performed or delivery expedited.