Dissertation
Category II fetal heart rate characteristics and cesarean delivery outcome: Descriptors and predictions for delivery outcome in low risk labor
University of Iowa
Doctor of Philosophy (PhD), University of Iowa
Autumn 2019
DOI: 10.17077/etd.005231
Abstract
Background: Cesarean delivery rates in the United States are higher than many other Western countries. Many researchers and specialists hypothesize that the use of continuous electronic fetal monitoring (CEFM) in labor may contribute to the decision to proceed with cesarean delivery. Currently, CEFM data is defined by a three-tiered category system, with the indeterminate category II encompassing 80% of all CEFM tracings. Little research exists that examines the association between the fetal heart rate (FHR) characteristics, their combinations and interactions observed in CEFM during the labor process in low risk pregnancies.
Methods: This study examined the category II FHR CEFM data, and maternal hospital records of low risk pregnant women who delivered at a Midwest, tertiary, academic hospital over 18 months. Category II FHR characteristics present in the two hours prior to delivery were collected by the primary investigator and a research assistant, both experienced labor and delivery nurses. All FHR characteristics were evaluated according to the definitions from the Eunice Kennedy Shriver National Institute of Child Health and Human Development. CEFM FHR data were combined with medical and demographic data taken from the maternal medical record.
Results: Of the 537 women included in the study, 24% delivered by cesarean for concerns with the FHR and 76% delivered vaginally. Women who delivered by cesarean had a median total time in category II of 43 minutes while women who delivered vaginally spent a median of 54 minutes in category II. The odds of cesarean delivery increased in the presence of abnormal baseline FHR (OR 3.07), variability (OR 1.68), late decelerations (OR 2.69) and prolonged decelerations (OR 1.97). After controlling for known covariates that can influence delivery method, only late and prolonged decelerations remained associated with cesarean delivery (OR 1.40, OR 1.51). Count of abnormal characteristics (which includes tachycardia, bradycardia, absent, minimal and marked variability, and variable, late and prolonged decelerations) was significantly associated with cesarean delivery with an average of 3 abnormal characteristics increasing the odds of cesarean by 19.62 times over those with an average of 1 abnormal characteristic.
Conclusion: While abnormal FHR characteristics that would place a CEFM tracing in category II were associated with cesarean delivery in low risk labor, once controlling for known covariates, the only characteristics that were predictive of cesarean were late and prolonged decelerations, and a new measurement, count of abnormal FHR characteristics. This new measurement could easily be calculated in real-time on labor and delivery units. The presence of many category II FHR characteristics in low risk labor may not be indicative of fetal hypoxia and the need to proceed with cesarean delivery.
Details
- Title: Subtitle
- Category II fetal heart rate characteristics and cesarean delivery outcome: Descriptors and predictions for delivery outcome in low risk labor
- Creators
- Emily Ann Miller
- Contributors
- Mary K Clark (Advisor)Ann Marie McCarthy (Committee Member) - University of Iowa, NursingMelissa Avery (Committee Member)Mark Santillan (Committee Member)Julie Vignato (Committee Member)
- Resource Type
- Dissertation
- Degree Awarded
- Doctor of Philosophy (PhD), University of Iowa
- Degree in
- Nursing
- Date degree season
- Autumn 2019
- DOI
- 10.17077/etd.005231
- Publisher
- University of Iowa
- Number of pages
- xiv, 137 pages
- Copyright
- Copyright 2019 Emily Ann Miller
- Language
- English
- Description illustrations
- color illustrations, facsimiles
- Description bibliographic
- Includes bibliographical references (pages 120-131)
- Public Abstract (ETD)
Cesarean deliveries rates are higher in the U.S. than many other Western countries and are associated with adverse outcomes. One reason for the high rate provided is the use of continuous electronic fetal monitoring (CEFM) in labor. CEFM tracings are currently divided into 3 categories: category I (well-oxygenated fetus), category II (indeterminate), and category III (fetus not well-oxygenated). Roughly 80% of all CEFM tracings fall into category II.
This study examined category II CEFM tracings in the last 2 hours of labor to determine if any particular fetal heart rate (FHR) characteristics or combinations thereof in low risk patients (mothers and fetuses with no underlying health issues) were associated with cesarean.
This study found that when limiting the study to only low risk patients, very few category II FHR characteristics were good indicators of the need to proceed with a cesarean delivery when accounting for circumstances known to contribute to the increased risk for cesarean. The only FHR characteristics that were good indicators were two types of drops in the FHR, called late and prolonged decelerations, and a new measurement created for this study, count of abnormal FHR characteristics.
Having one of the decelerations increased the risk of cesarean by 1.4-1.5 times. Having abnormal FHR characteristics increased the odds of a cesarean delivery over 19 times compared to having just 1 abnormal FHR characteristic. Counting abnormal FHR characteristics can be easily done on labor and delivery units and may be a better measurement of the well-being of a low risk fetus during labor.
- Academic Unit
- Nursing
- Record Identifier
- 9983779598802771
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