Electronic Fetal Monitoring:Management and Standard of Care Part 2
What Should We Do With Category 2?
For better or worse, electronic fetal monitoring has become a mainstay of fetal surveillance. Due to legal issues relating to failures in recognition and intervention with electronic fetal monitoring, several national associations have defined "graded categories" of tracing abnormalities, along with recommendations for interventions specific to the various categories. (Cat I,Cat II,Cat III.1 c
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Being able to determine the normal and abnormal ends of the categorial spectrum is not difficult. However, most fetal monitoring tracings do not reside at these extremes.2 Only 16% of vaginal births will reflect normal EFM tracing baselines with normal variability and no decelerations for the entire labor (Cat 1 - NICHD). Most normal labors will display some form of deceleration which will shift the tracing to Category II. In fact, the vast majority of tracings from babies with metabolic acidemia (MA) can be found in Category II.
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The need to identify which types of decelerations are benign and which are associated with MA continues to occupy researchers. Variable decelerations are considered the most common and range from minor and intermittent, to those that are repetitive and deep.3 The NICHD has termed variable decelerations with slow return to baseline, and "shoulders" or overshoot as belonging in Category II.
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One purpose of the Hamilton study was to determine which types of variable decelerations are associated with metabolic acidemia. The study confirms that infants born with MA were associated with more decelerations, more contractions, and less accelerations when compared with those with normal umbilical artery gases. Graded classifications of tracings have proved important for interpretation and management of fetal tracings. However, the middle level between Category I Category III spans a large spectrum of EFM tracings ranging from "near normal"to "very concerning".
The present study identifies variable decelerations that are associatied with MA and those that were not. Accelerations and variable decelerations without internal variability were significantly discriminating for MA, along with decels that were wide, prolonged, reaching the 60's, smooth, and, also, without internal variability.4
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A study by Bakker, et al determined that increased uterine activity (UA) was significantly associated with a higher incidence of umbilical artery pH of 7.11 or less. This paper underscored that EFM remains surrounded in controversy and has significant limitations. For instance, fetal heart rate patterns are not standardized, having poor reliability which leads to interventions that fail to improve fetal outcomes.5
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Unfortunately, the influence of uterine activity has not been sufficiently addressed in the literature. Excessive uterine activity may adversely affect a fetus, demonstrated by decreased variability, late decelerations, and prolonged decelerations. Additional authors consider excessive uterine activity as the most frequent cause of late decelerations (Freeman and Sheaker). Fetal outcomes were examined and increased uterine activity during the first and second stage of labor were found to be associated with increased incidences of lower pH in the umbilical artery. Increased uterine activity was significantly associated with a higher incidence of umbilical artery pH of 7.11 or less.
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Physical evidence for uterine activity-induced fetal acidosis at birth included the following observations: when uterine contractions were >30mmHg. The maternal uterine spiral arteries were compressed and "placental perfusion was strangulated".6 Maternal pushing efforts increased intrauterine pressure which resulteded in further compression of the spiral arteries. Excessive uterine activity also led to hyperstimulation and tachysystole by shortening relaxation time between contractions. These negative effects were noted during the last hour of the first stage of labor and the entire second stage.7
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Uterine contraction monitoring is rarely mentioned but studies have shown that it may deserve full attention as it pertains to adverse fetal outcomes. Uterine activity monitoring deserves a more prominant role in day-to-day obstetrical practice.8
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1 Emily Hamilton, Phillip Warrick & Daniel OutlineThe Journal of Maternal-Fetal and Neonatal Medicine. 2011, 1-6 Early Outline. Page 1
2 Ibid. pg 1
3 Ibid. pg 1
4 Ibid. pg 4
5 P.C.A. M. Bakker, MD;P.H. et.al. American Journal of Obstetrics and Gynecology, 2007;196;313,e1-313.e6. p.313e4
6 Ibid. 314e4
7 Ibid. 313e5
8 Ibid. 313e5 - final paragraph.
https://www.midwivesontrial.com (continued; Part 3 at website)