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Categorization of Fetal Heart Rate Decelerations in American and European Practice: Importance and Imperative of Avoiding Framing and Confirmation Biases.

Sholapurkar SL - J Clin Med Res (2015)

Bottom Line: This critical analysis debates pros and cons of significant anchoring/framing and confirmation biases in defining different types of decelerations based primarily on the shape (slope) or time of descent.These decelerations are benign, most likely and mainly a result of head-compression and hence should be called "early" rather than "variable".Such meaningful categorization, apart from being a scientific necessity, could improve the practical performance of three-tier FHR interpretation systems and possibly application of dependent complementary techniques like fetal ECG/pulse oximetry/computer-aided analysis, thus facilitating future progress in the field of intrapartum fetal monitoring.

View Article: PubMed Central - PubMed

Affiliation: Department of Obstetrics and Gynaecology, Royal United Hospital Bath NHS Trust, Bath, UK. Email: s.sholapurkar@nhs.net.

ABSTRACT
Interpretation of electronic fetal monitoring (EFM) remains controversial and unsatisfactory. Fetal heart rate (FHR) decelerations are the commonest aberrant feature on cardiotocographs and considered "center-stage" in the interpretation of EFM. A recent American study suggested that the lack of correlation of American three-tier system to neonatal acidemia may be due to the current peculiar nomenclature of FHR decelerations leading to loss of meaning. The pioneers like Hon and Caldeyro-Barcia classified decelerations based primarily on time relationship to contractions and not on etiology per se. This critical analysis debates pros and cons of significant anchoring/framing and confirmation biases in defining different types of decelerations based primarily on the shape (slope) or time of descent. It would be important to identify benign early decelerations correctly to avoid unnecessary intervention as well as to improve the positive predictive value of the other types of decelerations. Currently the vast majority of decelerations are classed as "variable". This review shows that the most common rapid decelerations during contractions with trough corresponding to peak of contraction cannot be explained by "cord-compression" hypothesis but by direct/pure (defined here as not mediated through baro-/chemoreceptors) or non-hypoxic vagal reflex. These decelerations are benign, most likely and mainly a result of head-compression and hence should be called "early" rather than "variable". Standardization is important but should be appropriate and withstand scientific scrutiny. Significant framing and confirmation biases are necessarily unscientific and the succeeding three-tier interpretation systems and structures embodying these biases would be dysfunctional and clinically unhelpful. Clinical/pathophysiological analysis and avoidance of flaws/biases suggest that a more physiological and scientific categorization of decelerations should be based on time relationship to contractions alone irrespective of shape or descent time as indeed proposed by pioneers like Hon and Caldeyro-Barcia. Such meaningful categorization, apart from being a scientific necessity, could improve the practical performance of three-tier FHR interpretation systems and possibly application of dependent complementary techniques like fetal ECG/pulse oximetry/computer-aided analysis, thus facilitating future progress in the field of intrapartum fetal monitoring.

No MeSH data available.


Related in: MedlinePlus

Diagrammatic representation of early, late and variable decelerations as practiced in British Obstetrics before 2007 (reproduced with kind permission from “Principles of Obstetrics” by Bryan Hibbard, 1988) [20]. Note the apparent rapid descent of early decelerations.
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Figure 4: Diagrammatic representation of early, late and variable decelerations as practiced in British Obstetrics before 2007 (reproduced with kind permission from “Principles of Obstetrics” by Bryan Hibbard, 1988) [20]. Note the apparent rapid descent of early decelerations.

Mentions: Experiments in sheep showed that “clamping” of umbilical cord (partial or complete) was associated with rapid FHR decelerations [1]. Whether that is comparable to what happens during labor contractions or not, the decelerations with rapid descent were assumed to indicate “cord compression” and hence called “variable”. By corollary, decelerations due to head compression (early) were postulated to have slow descent and defined as such. This convenient differentiation soon became ingrained in practice [8-11, 23]. An arbitrary cut-off of 30 s was selected to differentiate rapid from gradual decelerations [10, 11]. Plentiful evidence (see below) and American/British expert observation (Fig. 4) that the head compression also causes “rapid” decelerations tends to be disregarded now (confirmation bias?).


Categorization of Fetal Heart Rate Decelerations in American and European Practice: Importance and Imperative of Avoiding Framing and Confirmation Biases.

Sholapurkar SL - J Clin Med Res (2015)

Diagrammatic representation of early, late and variable decelerations as practiced in British Obstetrics before 2007 (reproduced with kind permission from “Principles of Obstetrics” by Bryan Hibbard, 1988) [20]. Note the apparent rapid descent of early decelerations.
© Copyright Policy - open access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4522983&req=5

Figure 4: Diagrammatic representation of early, late and variable decelerations as practiced in British Obstetrics before 2007 (reproduced with kind permission from “Principles of Obstetrics” by Bryan Hibbard, 1988) [20]. Note the apparent rapid descent of early decelerations.
Mentions: Experiments in sheep showed that “clamping” of umbilical cord (partial or complete) was associated with rapid FHR decelerations [1]. Whether that is comparable to what happens during labor contractions or not, the decelerations with rapid descent were assumed to indicate “cord compression” and hence called “variable”. By corollary, decelerations due to head compression (early) were postulated to have slow descent and defined as such. This convenient differentiation soon became ingrained in practice [8-11, 23]. An arbitrary cut-off of 30 s was selected to differentiate rapid from gradual decelerations [10, 11]. Plentiful evidence (see below) and American/British expert observation (Fig. 4) that the head compression also causes “rapid” decelerations tends to be disregarded now (confirmation bias?).

Bottom Line: This critical analysis debates pros and cons of significant anchoring/framing and confirmation biases in defining different types of decelerations based primarily on the shape (slope) or time of descent.These decelerations are benign, most likely and mainly a result of head-compression and hence should be called "early" rather than "variable".Such meaningful categorization, apart from being a scientific necessity, could improve the practical performance of three-tier FHR interpretation systems and possibly application of dependent complementary techniques like fetal ECG/pulse oximetry/computer-aided analysis, thus facilitating future progress in the field of intrapartum fetal monitoring.

View Article: PubMed Central - PubMed

Affiliation: Department of Obstetrics and Gynaecology, Royal United Hospital Bath NHS Trust, Bath, UK. Email: s.sholapurkar@nhs.net.

ABSTRACT
Interpretation of electronic fetal monitoring (EFM) remains controversial and unsatisfactory. Fetal heart rate (FHR) decelerations are the commonest aberrant feature on cardiotocographs and considered "center-stage" in the interpretation of EFM. A recent American study suggested that the lack of correlation of American three-tier system to neonatal acidemia may be due to the current peculiar nomenclature of FHR decelerations leading to loss of meaning. The pioneers like Hon and Caldeyro-Barcia classified decelerations based primarily on time relationship to contractions and not on etiology per se. This critical analysis debates pros and cons of significant anchoring/framing and confirmation biases in defining different types of decelerations based primarily on the shape (slope) or time of descent. It would be important to identify benign early decelerations correctly to avoid unnecessary intervention as well as to improve the positive predictive value of the other types of decelerations. Currently the vast majority of decelerations are classed as "variable". This review shows that the most common rapid decelerations during contractions with trough corresponding to peak of contraction cannot be explained by "cord-compression" hypothesis but by direct/pure (defined here as not mediated through baro-/chemoreceptors) or non-hypoxic vagal reflex. These decelerations are benign, most likely and mainly a result of head-compression and hence should be called "early" rather than "variable". Standardization is important but should be appropriate and withstand scientific scrutiny. Significant framing and confirmation biases are necessarily unscientific and the succeeding three-tier interpretation systems and structures embodying these biases would be dysfunctional and clinically unhelpful. Clinical/pathophysiological analysis and avoidance of flaws/biases suggest that a more physiological and scientific categorization of decelerations should be based on time relationship to contractions alone irrespective of shape or descent time as indeed proposed by pioneers like Hon and Caldeyro-Barcia. Such meaningful categorization, apart from being a scientific necessity, could improve the practical performance of three-tier FHR interpretation systems and possibly application of dependent complementary techniques like fetal ECG/pulse oximetry/computer-aided analysis, thus facilitating future progress in the field of intrapartum fetal monitoring.

No MeSH data available.


Related in: MedlinePlus