Fetal defenses against intrapartum head compression—implications for intrapartum decelerations and hypoxic-ischemic injury

Lear, Christopher A.; Westgate, Jenny A.; Ugwumadu, Austin; Stone, Peter; Tournier, Alexane; Gunn, Alistair J.

doi:10.1016/j.ajog.2021.11.1352

Cited by 19 publications

(17 citation statements)

References 57 publications

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“…However, if the interval between the contractions is too short, or placental function is compromised, prolonged impairment of oxygen delivery may lead to tissue hypoxia, metabolic acidaemia, and persistent reduction in fetal cerebral oxygenation 59–64 . If these episodes of hypoxaemia continue, fetal cardiac output is progressively compromised, leading to fetal hypotension and hypoperfusion, potentially resulting in hypoxic–ischemic brain injury 65–71 . The progressive worsening intrapartum fetal hypoxaemia can be observed as changes in baseline FHR and deeper FHR decelerations, 6,72,73 but once deeper decelerations are established there is typically little further change in FHR 74 .…”

Section: Fetal Adaptation During Labourmentioning

confidence: 99%

Increased variability of fetal heart rate during labour: a review of preclinical and clinical studies

Tarvonen

Lear

Andersson

et al. 2022

BJOG

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Increased fetal heart rate variability (FHRV) in intrapartum cardiotocographic recording has been variably defined and poorly understood, limiting its clinical utility. Both preclinical (animal) and clinical (human) evidence support that increased FHRV is observed in the early stage of intrapartum fetal hypoxaemia but can also be observed in a subset of fetuses during the preterminal stage of repeated hypoxaemia. This review of available evidence provides data and expert opinion on the pathophysiology of increased FHRV, its clinical significance and a stepwise approach regarding the management of this pattern, and propose recommendations for standardisation of related terminology.

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Section: Fetal Adaptation During Labourmentioning

confidence: 99%

Increased variability of fetal heart rate during labour: a review of preclinical and clinical studies

Tarvonen

Lear

Andersson

et al. 2022

BJOG

Self Cite

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“…The authors further hypothesized that these defenses might involve humoral factors [ 15 ]. However, fetal responses were augmented with repeated stimulation, which is likely due to the progressive accumulation of humoral factors [ 10 ]. Overall, these experiments demonstrated that periods of head compression such as during a typical, spontaneous delivery did not critically impair cerebral perfusion and were therefore, not associated with FHR decelerations.…”

Section: Synthesismentioning

confidence: 99%

“…Meanwhile, late decelerations were acknowledged to result from hypoxia. Recently, this etiological classification has been questioned by physiologists, leading to a reconceptualization of intrapartum decelerations [ 7 , 8 , 9 , 10 ]. The objective of this narrative review was to compare the old evidence with the new on pathophysiology behind fetal decelerations during labor.…”

Section: Introductionmentioning

confidence: 99%

Is It Time to Redefine Fetal Decelerations in Cardiotocography?

Xodo

Londero

2022

JPM

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Historically, fetal heart rate (FHR) decelerations were classified into “early”, “late”, and “variable” based on their relationship with uterine contractions. So far, three different putative etiologies were taken for granted. Recently, this belief, passed down through generations of birth attendants, has been questioned by physiologists. This narrative review aimed to assess the evidence on pathophysiology behind intrapartum FHR decelerations. This narrative review is based on information sourced from online peer-reviewed articles databases and recommendations from the major scientific societies in the field of obstetrics. Searches were performed in MEDLINE/PubMed, EMBASE, and Scopus and selection criteria included studies in animals and humans, where the physiology behind FHR decelerations was explored. The greater affinity for oxygen of fetal hemoglobin than the maternal, the unicity of fetal circulation, and the high anaerobic reserve of the myocardium, ensure adequate oxygenation to the fetus, under basal conditions. During acute hypoxic stress the efficiency of these mechanisms are increased because of the peripheral chemoreflex. This reflex, activated at each uterine contraction, is characterized by the simultaneous activation of two neural arms: the parasympathetic arm, which reduces the myocardial consumption of oxygen by decreasing the FHR and the sympathetic component, which promotes an intense peripheric vasoconstriction, thus centralizing the fetal blood volume. This review summarizes the evidence supporting the hypoxic origin of FHR decelerations, therefore archiving the historical belief that FHR decelerations have different etiologies, according to their shape and relationship with uterine contractions. The present review suggests that it is time to welcome the new scientific evidence and to update the CTG classification systems.

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“…There is considerable controversy over the role of mechanical factors in the genesis of abnormal FHR patterns and neurological injury (103,104). From a teleological perspective, mechanical Initially, this FHR pattern consists of absent variability, baseline tachycardia, variable deceleration with overshoot.…”

Section: Cranial Compressionmentioning

confidence: 99%

“…forces exerted on the fetal head during labor and delivery would seem to be as predictable an eventuality as the hypoxemic effects of uterine contractions and should generate similar robust, protective responses. In fact, there is clear evidence of central receptors sensitive to even subtle changes in cerebral blood flow or perhaps even to astrocyte (105) detection of distortion of cerebral vessel walls that act to maintain cerebral perfusion even absent systemic acidemia (104). Furthermore, there are a collection of primitive homeostatic reflexes quite active in the term fetus (dive reflex, etc.)…”

Section: Cranial Compressionmentioning

confidence: 99%

Approaches to Preventing Intrapartum Fetal Injury

et al. 2022

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Electronic fetal monitoring (EFM) was introduced into obstetric practice in 1970 as a test to identify early deterioration of fetal acid-base balance in the expectation that prompt intervention (“rescue”) would reduce neonatal morbidity and mortality. Clinical trials using a variety of visual or computer-based classifications and algorithms for intervention have failed repeatedly to demonstrate improved immediate or long-term outcomes with this technique, which has, however, contributed to an increased rate of operative deliveries (deemed “unnecessary”). In this review, we discuss the limitations of current classifications of FHR patterns and management guidelines based on them. We argue that these clinical and computer-based formulations pay too much attention to the detection of systemic fetal acidosis/hypoxia and too little attention not only to the pathophysiology of FHR patterns but to the provenance of fetal neurological injury and to the relationship of intrapartum injury to the condition of the newborn. Although they do not reliably predict fetal acidosis, FHR patterns, properly interpreted in the context of the clinical circumstances, do reliably identify fetal neurological integrity (behavior) and are a biomarker of fetal neurological injury (separate from asphyxia). They provide insight into the mechanisms and trajectory (evolution) of any hypoxic or ischemic threat to the fetus and have particular promise in signaling preventive measures (1) to enhance the outcome, (2) to reduce the frequency of “abnormal” FHR patterns that require urgent intervention, and (3) to inform the decision to provide neuroprotection to the newborn.

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Fetal defenses against intrapartum head compression—implications for intrapartum decelerations and hypoxic-ischemic injury

Cited by 19 publications

References 57 publications

Increased variability of fetal heart rate during labour: a review of preclinical and clinical studies

Increased variability of fetal heart rate during labour: a review of preclinical and clinical studies

Is It Time to Redefine Fetal Decelerations in Cardiotocography?

Approaches to Preventing Intrapartum Fetal Injury

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