Is the hypothesis that the commonest fetal heart rate decelerations are caused by peripheral chemoreflex due to fetal hypoxaemia correct?

Sholapurkar, Shashikant L.

doi:10.1113/jp274478

Cited by 1 publication

(3 citation statements)

References 10 publications

(37 reference statements)

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“…Even if UCO is one of the causes of fetal bradycardia, the conclusion may be interpreted only in the case of complete and brief UCO during labor, particularly during cord prolapse. Other mechanisms have been described, such as placenta or head compression, but the conclusions cannot be extrapolated to this present study [7,8]. Moreover, we did not evaluate the effect of uterine contractions on the onset of FHR decelerations, as observed in human fetuses, or the role of uterine contractions on sympathetic or parasympathetic stimulation during labor.…”

Section: Discussionmentioning

confidence: 64%

“…These decelerations may result, at least in part, from umbilical cord compression, such as during cord prolapse. However, cord compression is unlikely to be the main cause of FHR decelerations in the majority of labors [7][8][9]. Indeed, fetal head compression has been reported, by Parer et al, to be responsible for early FHR decelerations, due to a transient change in cerebral blood flow resulting in vagal discharge [32].…”

Section: Discussionmentioning

confidence: 99%

“…Heart rate (HR) is controlled by parasympathetic activity through M2 muscarinic receptors on nodal cells and by sympathetic activity mediated by ß1-adrenergic receptors on cardiac pacemaker cells [ 5 ]. However, the parasympathetic output and sympathetic output at different time points during and after FHR deceleration remain incompletely understood [ 3 , 7 , 8 ]. A better understanding of the sequence of ANS activity during FHR may help decipher which reflexes trigger FHR decelerations [ 9 ].…”

Section: Introductionmentioning

confidence: 99%

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Roles of parasympathetic outflow and sympathetic outflow in the cardiovascular response to brief umbilical cord occlusion in fetal sheep

et al. 2021

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Fetal heart rate (FHR) deceleration is the most common change seen during labor. The role of the autonomic nervous system in regulating the fetal cardiovascular response during multiple uterine contractions has been well-established. However, the mechanism underlying the hemodynamic response remains unclear and the specific reflex that mediates the cardiovascular modifications is still controversial. This study aimed to determine the role of the sympathetic and parasympathetic systems on fetal hemodynamics in complete cord occlusion. Chronically instrumented fetal sheep were randomized to receive an intravenous injection of atropine 2.5 mg (n = 8), propranolol 5 mg (n = 7), atropine and propranolol (n = 7), or a control protocol (n = 9), followed by three episodes of 1-minute umbilical cord occlusion repeated every 5 minutes. Cord compression induces a rapid decrease in the FHR and a rapid increase in MAP. The decrease in FHR is caused by an increase in parasympathetic activity, (atropine and atropine-propranolol abolish the FHR response to the occlusion). The change in FHR during occlusion was not modified by propranolol injection, showing no effect of sympathetic tone. The increase in MAP during occlusion was similar in the four protocols. After releasing occlusion, the FHR was still lower than that at baseline due to a sustained parasympathetic tone. Suppression of the parasympathetic output to the cardiovascular system unmasks an increase in the FHR above baseline values. The lower FHR with the propranolol protocol further supports an increase in myocardial β-adrenoceptor stimulation after cord release. The increase in MAP after cord release was similar in the four protocols, except after the early stage of interocclusion period in atropine protocol. Four minutes after cord release, the FHR returned to baseline irrespective of the drugs that were infused, thereby showing recovery of ANS control. Blood gases (pH, PaCO2, PaO2) and plasma lactate concentrations was similar between the four protocols at the end of three applications of UCO. Complete cord compression-induced deceleration is likely due to acute activation of parasympathetic output. β-adrenoceptor activity is involved in the increase in FHR after cord release. Understanding the reflexes involved in FHR deceleration may help us understand the mechanisms underlying fetal autonomic adaptation during cord occlusion.

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Section: Discussionmentioning

confidence: 64%

Section: Discussionmentioning

confidence: 99%