Is It Time to Redefine Fetal Decelerations in Cardiotocography?
Abstract
:1. Introduction
2. Materials and Methods
3. Synthesis
3.1. Early Decelerations
3.2. Variable Decelerations
3.3. Late Decelerations
3.4. New Insights into the Pathophysiology of Fetal Intrapartum Decelerations
3.5. The State of the Art of Current Intrapartum Cardiotocography
4. Limitations to the Overview
5. Conclusions
Author Contributions
Funding
Institutional Review Board Statement
Informed Consent Statement
Data Availability Statement
Acknowledgments
Conflicts of Interest
References
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Decelerations | ACOG 2009 | FIGO 2015 | NICE 2014 |
---|---|---|---|
Early | Usually symmetrical gradual decrease and return of the FHR associated with a uterine contraction. A gradual FHR decrease is defined as from the onset to the FHR nadir of 30 s or more. The decrease in FHR is calculated from the onset to the nadir of the deceleration. The nadir of the deceleration occurs at the same time as the peak of the contraction. In most cases the onset, nadir, and recovery of the deceleration are coincident with the beginning, peak, and ending of the contraction, respectively. | shallow, short-lasting, with normal variability within the deceleration and are coincident with contractions. They are believed to be caused by fetal head compression and do not indicate fetal hypoxia/acidosis. | |
Late | Usually symmetrical gradual decrease and return of the FHR associated with a uterine contraction. A gradual FHR decrease is defined as from the onset to the FHR nadir of 30 s or more. The decrease in FHR is calculated from the onset to the nadir of the deceleration. The deceleration is delayed in timing, with the nadir of the deceleration occurring after the peak of the contraction. In most cases, the onset, nadir, and recovery of the deceleration occur after the beginning, peak, and ending of the contraction, respectively. | U-shaped with a gradual onset and/or a gradual return to the baseline and/or reduced variability within the deceleration. Gradual onset and return occurs when more than 30 s elapses between the beginning/end of a deceleration and its nadir. When contractions are adequately monitored, late decelerations start more than 20 seconds after the onset of a contraction, have a nadir after the acme, and a return to the baseline after the end of the contraction. These decelerations are indicative of a chemoreceptor-mediated response to fetal hypoxemia. In the presence of a tracing with no accelerations and reduced variability, the definition of late decelerations also includes those with an amplitude of 10−15 bpm. | Present for over 30 min; they do not improve with conservative measures and occurring with over 50% of contractions |
Variable | Visually apparent abrupt decrease in FHR An abrupt FHR decrease is defined as from the onset of the deceleration to the beginning of the FHR nadir of less than 30 s. The decrease in FHR is calculated from the onset to the nadir of the deceleration. The decrease in FHR is 15 beats per minute or greater, lasting 15 seconds or greater, and less than 2 min in duration. When variable decelerations are associated with uterine contractions, their onset, depth, and duration commonly vary with successive uterine contractions. | V-shaped and exhibit a rapid drop (onset to nadir in less than 30 s), good variability within the deceleration, rapid recovery to the baseline, varying size, shape, and relationship to uterine contractions. They constitute the majority of decelerations during labor, and translate a baroreceptor-mediated response to increased arterial pressure, as occurs with umbilical cord compression. They are seldom associated with an important degree of fetal hypoxia/acidosis, unless they evolve to exhibit a U-shaped component, reduced variability within the deceleration, and/or their individual duration exceeds 3 min (prolonged decelerations). | Dropping from baseline by 60 beats/minute or less and for 30–90 min taking 60 seconds or less to recover. They are present for over 90 min and occurring with over 50% of contractions. OR Dropping from baseline by more than 60 beats/minute or taking over 60 seconds to recover. They are present for up to 30 min and occurring with over 50% of contractions. |
Deceleration Type | Historical Belief | Why Historical Belief Is Misleading | New Insights in Pathophysiology of Fetal Decelerations |
---|---|---|---|
Early decelerations | -Results from head compression during fetal head engagement in the birth canal; -Considered benign and not caused by hypoxia; | -Only head compression severe enough to determine profound cerebral hypoperfusion triggers FHR decelerations; -Periods of head compression such as during spontaneous delivery do not critically impair cerebral perfusion and are not associated with FHR decelerations; | In case of extreme increases in intracranial pressure decelerations are not benign, being the fetal response to severe cerebral hypoperfusion |
Variable decelerations | -Results from cord compression, therefore, having a variable relationship with contractions; -Potentially eliminable by changing the maternal position; | -The baroreflex mediated mechanism implicates that hypertension is consistently observed with complete cord occlusion, which was not experimentally confirmed; -The Bezold-Jarish reflex implicates that hypovolemia due to umbilical cord compression leads to a decreased venous return to the fetal heart, which in turn leads to the activation of the vagal reflex, thus provoking deceleration. However, in fetal sheep this reflex was not activated by reduced cardiac pressures. Moreover, when activated, this reflex induced a delayed deceleration, which is not consistent with the typical pattern of the variable deceleration. | These decelerations originate from hypoxemia, which is caused by at least a 50% reduction in intervillous perfusion, and are mediated by the peripheral chemoreflex |
Late decelerations | -Results from utero-placental insufficiency. | No experimental evidence supports the conclusion that these decelerations are associated with a greater physiological challenge than early or variable decelerations. | Rhese decelerations originate from hypoxemia, which is caused by at least a 50% reduction in intervillous perfusion, and are mediated by the peripheral chemoreflex. |
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Xodo, S.; Londero, A.P. Is It Time to Redefine Fetal Decelerations in Cardiotocography? J. Pers. Med. 2022, 12, 1552. https://doi.org/10.3390/jpm12101552
Xodo S, Londero AP. Is It Time to Redefine Fetal Decelerations in Cardiotocography? Journal of Personalized Medicine. 2022; 12(10):1552. https://doi.org/10.3390/jpm12101552
Chicago/Turabian StyleXodo, Serena, and Ambrogio P. Londero. 2022. "Is It Time to Redefine Fetal Decelerations in Cardiotocography?" Journal of Personalized Medicine 12, no. 10: 1552. https://doi.org/10.3390/jpm12101552