Understanding Fetal Heart Rate Patterns That May Predict Antenatal and Intrapartum Neural Injury

Peripheral chemoreflex control of fetal heart rate decelerations overwhelms the baroreflex during brief umbilical cord occlusions in fetal sheep

“…Finally, it is of course important to caution that, potentially at least, there could be differences in the response to UCO between sheep and human fetuses. Nonetheless, many studies in chronically instrumented fetal sheep have effectively translated into improved clinical understanding (Dalton et al J Physiol 598.20 1977Hanson, 1988;Giussani et al 1993;Westgate et al 1999b;Lear et al 2018b).…”

Computer‐based intrapartum fetal monitoring and beyond: A review of the 2nd Workshop on Signal Processing and Monitoring in Labor (October 2017, Oxford, UK)

“…These modern clinical findings are not minor tweaks to CTG interpretation, but illustrate that the physiology underlying CTG is not what we were taught to expect. This is paralleled by a much deeper understanding of fetal physiology, through well-designed animal studies 70 . Many of these animal studies involve highly structured sequences of repeated umbilical cord occlusion modelling the intermittent nature of hypoxemia associated with uterine contractions 71 , but are in no way designed to truly reflect the complex and dynamic nature of human labor.…”

Reply to “Letter to the Editor: Bezold–Jarisch reflex in the near-term fetus during labor: a matter of time”

“…First, the key efferent response of the Bezold-Jarisch reflex that would distinguish it from the peripheral chemoreflex is peripheral vasodilation due to sympathetic nervous activity withdrawal (5,6). We have shown using chemical sympathectomy with 6-hydroxy-dopamine that sympathetic nervous system-mediated peripheral vasoconstriction is maintained throughout a prolonged series of repeated UCOs despite the onset of arterial hypotension (6,7).…”

“…First, the key efferent response of the Bezold-Jarisch reflex that would distinguish it from the peripheral chemoreflex is peripheral vasodilation due to sympathetic nervous activity withdrawal (5,6). We have shown using chemical sympathectomy with 6-hydroxy-dopamine that sympathetic nervous system-mediated peripheral vasoconstriction is maintained throughout a prolonged series of repeated UCOs despite the onset of arterial hypotension (6,7). In a preliminary analysis of a series of 1-min repeated UCOs that resulted in severe hypotension (<20 mmHg on the final 2 UCOs), we have found that profound decreases in femoral blood flow and vascular conductance (FBF and FVC, respectively) continue to occur during the UCOs to values well-below baseline levels, despite the presence of severe hypotension.…”