6/14/2019 Disclosures Electronic Fetal Monitoring The Good, the Bad and the Ugly I have nothing to disclose. Jeanne S. Sheffield, MD Maternal-Fetal Medicine Johns Hopkins Medicine The History of Fetal Monitoring The History of Fetal Monitoring • 1600s Marsac first detected a fetal heart • 1917 fetoscope developed by David Hillis rate • Intermittent auscultation guidance • 1818 Mayor and Kergaradec auscultated – 1968 24,863 IA labors reviewed fetal heart sounds using an ear to the • Not a reliable indicator of fetal distress maternal abdomen • Used for over 40 years before first RCT • Multiple attempts at capturing the fetal – Used for detection of viability ECG from 1906 • 1833 Kennedy published guidelines for – 1958 Hon able to capture continuous fetal fetal distress based on fetal auscultation ECG and by the 1960s EFM systems were in • 1893 Von Winkel criteria for fetal distress commercial use 1
6/14/2019 The History of Fetal Monitoring Limitations of EFM • 1972 Hon and Hess developed the fetal • While it is the most commonly performed scalp electrode obstetric procedure….. • By 1975, ~ 20% of labors – Failed to decrease rates of cerebral palsy and neurologic injury were monitored by EFM – No overall decrease in perinatal death • It took over 10 years after EFM was being – Higher operative delivery used consistently before the first RCT was • Medicolegal issues performed. • Now over 85% of deliveries in the United States are monitored using EFM Fetal Heart Rate Monitoring Electronic Fetal Monitoring Frequency • External monitoring • EFM versus intermittent auscultation – Ultrasound doppler principle – Term, low risk… • No meconium staining, intrapartum bleeding, • Internal (Direct) monitoring abnormal fetal test results, no risk of fetal – Bipolar spiral electrode is attached directly to academia developing, maternal conditions that the fetus might affect fetal well-being and no oxytocin induction or augmentation – Fetal cardiac signal is amplified : the R-wave voltage is most reliably detected. Time between R waves is calculated and seen as beat-to-beat variability 2
6/14/2019 Intermittent Auscultation Standardization of EFM Nomenclature • FHR assessment every 30 minutes in the • NICHD 1997 Fetal Monitoring Research active phase of the first stage of labor and Planning Workshop every 15 minutes in the second stage – Standardized, unambiguous definitions • If risk factors develop, moves to every 15 – Research recommendations, especially to address the poor specificity to predict fetal minutes and every 5 minutes compromise • NICHD, ACOG and SMFM 2008 Workshop – Update the definitions for CTG patterns – Research prioroities Let’s All Speak the Same Language Improving Patient Safety and Outcomes Obstet Gynecol 2008 • Assumptions – Visual interpretation (but left room for AI) – Direct fetal electrode OR external Doppler device using autocorrelation technique – Features categorized as baseline, periodic (with uterine contractions) or episodic (not associated with contractions) 3
6/14/2019 Obstet Gynecol 2008 • Assumptions Obstet Gynecol 2008 – Patterns categorized as abrupt or gradual Uterine contractions: number of contractions in a 10 – No distinction made between short and long term minute window averaged over 30 minutes variability - Normal: ≤5 contractions in 10 minutes – FHR tracings should be evaluated in the context - Tachysystole: >5 contractions in a 10 minute of clinical factors e.g. EGA, maternal physiologic window state, fetal conditions - Hyperstimulation and hypercontractility were – FHR patterns evolve over time abandoned Fetal Heart Rate Patterns • Baseline: mean FHR rounded to increments of 5 bpm during a 10 minute window, excluding accelerations and decelerations and marked variability (>25bpm) – Bradycardia <110 bpm – Tachycardia >160 bpm • Baseline FHR Variability: 10 minute window – Absent – Minimal: amplitude ≥ 5 bpm – Moderate: amplitude 6-25 bpm – Marked: amplitude > 25 bpm 4
6/14/2019 Fetal Heart Rate Variability Fetal Heart Rate Patterns • Acceleration: abrupt (onset to peak <30 seconds) increase in FHR – Peak must be ≥ 15 bpm, lasting ≥15 seconds • Before 32 weeks, peak ≥ 10 bpm and duration ≥ 10 seconds – Prolonged: ≥ 2 minutes but < 10 minutes – Baseline change: ≥ 10 minutes Marked Variability or Saltatory LTV ≥ 25 bpm Causes – fetal activity, compensatory response to hypoxemia Fetal Heart Rate Patterns • Decelerations – Prolonged: decrease in FHR ≥ 15 bpm, lasting ≥ 2 minutes but <10 minutes – Sinusoidal: Visually apparent, smooth sine wave-like undulating pattern with a cycle frequency of 3-5/minute, persisting ≥ 20 minutes 5
6/14/2019 Fetal Heart Rate Categorization Fetal Heart Rate Patterns • Three-tier system • Decelerations – At a specific point in time – the FHT may – Recurrent if occur with ≥ 50% of uterine contractions in move back and forth over time any 20 minute window – Limited management discussion – Intermittent if occur <50% of uterine contractions in any – Cannot predict cerebral palsy 20 minute window – Unknown the predictive value of grading systems that utilize the depth of the deceleration NORMAL Strongly predictive of normal acid-base status Other Important Notes… • FHTs need to be interpreted in the clinical context INDETERMINATE • FHR accelerations (spontaneous or induced) reliably predicts the absence of fetal metabolic acidemia – The absence does NOT reliably predict acidemia however.. • Moderate FHR variability also predicts the ABNORMAL absence of fetal metabolic acidemia – Minimal, absent or marked unclear Predictive of abnormal fetal acid-base status 6
6/14/2019 Fetal Pulse Oximetry • 2000 FDA approved a fetal pulse oximetry 5341 nulliparous women in early labor were randomized to open system to use as an adjunct to EFM or masked fetal pulse oximetry. – Sensor was placed through the cervix alongside the fetal face to measure fetal oxygen saturation. – Early studies showed some correlation between fetal metabolic acidosis and fetal saturation readings in the setting of a non- reassuring FHT. 2014 Cochrane Collaboration ST Segment Analysis (STAN) • Fetal Pulse Oximetry did not reduce the • Approved by the FDA in 2005 but used in overall Cesarean section rate Europe for two decades • A better method than pulse oximetry is • Standard cardiotocography (CTG) with required to enhance the overall evaluation concurrent assessment of the fetal ECG. of fetal well-being in labour. – Normal ST waveform is horizontal or upward sloping – Normal T-wave has a constant amplitude – Changes in the waveforms may reflects fetal hypoxia 7
6/14/2019 11,108 term women in early to active labor with a singleton 2015 gestation were randomized to open or masked ECG ST-Segment No difference in analysis Cesarean delivery or operative delivery The Pros and Cons of EFM ST Segment Analysis (STAN) • Screening test with poor positive • 2015 Cochrane Review Fetal ECG for predictive value, esp. in low risk women Fetal Monitoring During Labor • No randomized clinical trials other than a – Over 27,000 women from 7 trials comparison to IA • No difference in Cesarean rate, severe fetal – Increased Cesarean delivery rates acidosis or neonatal encephalopathy, no decrease in low 5 minute Apgar score – Increased operative delivery rates • Fewer fetal scalp samples and operative vaginal – Did not reduce perinatal mortality deliveries (marginal) – Did not reduce the risk of cerebral palsy • Several studies since this time have had – Did decrease risk of neonatal seizures similar findings. • High intra- and intervariability 8
6/14/2019 EFM and Cerebral Palsy • EFM does not predict cerebral palsy and we should not expect it to – PPV of a non-reassuring pattern of a singleton infant >2500gm is 0.14% (1000 abnormal FHTs, 1-2 will develop cerebral palsy) – False positive rate of >99% Nelson et al NEJM 1996 9
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