Disclosures Electronic Fetal Monitoring The Good, the Bad and the - - PowerPoint PPT Presentation

6/14/2019 1

Electronic Fetal Monitoring The Good, the Bad and the Ugly

Jeanne S. Sheffield, MD Maternal-Fetal Medicine Johns Hopkins Medicine

Disclosures

I have nothing to disclose.

The History of Fetal Monitoring

• 1600s Marsac first detected a fetal heart

rate

• 1818 Mayor and Kergaradec auscultated

fetal heart sounds using an ear to the maternal abdomen

– Used for detection of viability

• 1833 Kennedy published guidelines for

fetal distress based on fetal auscultation

• 1893 Von Winkel criteria for fetal distress

The History of Fetal Monitoring

• 1917 fetoscope developed by David Hillis
• Intermittent auscultation guidance

– 1968 24,863 IA labors reviewed

• Not a reliable indicator of fetal distress
• Used for over 40 years before first RCT
• Multiple attempts at capturing the fetal

ECG from 1906

– 1958 Hon able to capture continuous fetal ECG and by the 1960s EFM systems were in commercial use

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The History of Fetal Monitoring

• 1972 Hon and Hess developed the fetal

scalp electrode

• By 1975, ~ 20% of labors

were monitored by EFM

• It took over 10 years after EFM was being

used consistently before the first RCT was performed.

• Now over 85% of deliveries in the United

States are monitored using EFM

Limitations of EFM

• While it is the most commonly performed
• bstetric procedure…..

– Failed to decrease rates of cerebral palsy and neurologic injury – No overall decrease in perinatal death – Higher operative delivery

• Medicolegal issues

Electronic Fetal Monitoring

• External monitoring

– Ultrasound doppler principle

• Internal (Direct) monitoring

– Bipolar spiral electrode is attached directly to the fetus – 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

Fetal Heart Rate Monitoring Frequency

• EFM versus intermittent auscultation

– Term, low risk…

• No meconium staining, intrapartum bleeding,

abnormal fetal test results, no risk of fetal academia developing, maternal conditions that might affect fetal well-being and no oxytocin induction or augmentation

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Intermittent Auscultation

• FHR assessment every 30 minutes in the

active phase of the first stage of labor and every 15 minutes in the second stage

• If risk factors develop, moves to every 15

minutes and every 5 minutes

Standardization of EFM Nomenclature

• NICHD 1997 Fetal Monitoring Research

Planning Workshop

– Standardized, unambiguous definitions – Research recommendations, especially to address the poor specificity to predict fetal 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)

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Obstet Gynecol 2008

• Assumptions

– Patterns categorized as abrupt or gradual – No distinction made between short and long term variability – FHR tracings should be evaluated in the context

• f clinical factors e.g. EGA, maternal physiologic

state, fetal conditions – FHR patterns evolve over time

Obstet Gynecol 2008

Uterine contractions: number of contractions in a 10 minute window averaged over 30 minutes

• Normal: ≤5 contractions in 10 minutes
• Tachysystole: >5 contractions in a 10 minute

window

• Hyperstimulation and hypercontractility were

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

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Fetal Heart Rate Variability

Marked Variability or Saltatory

LTV ≥ 25 bpm Causes – fetal activity, compensatory response to hypoxemia

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

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

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Fetal Heart Rate Patterns

• Decelerations

– Recurrent if occur with ≥ 50% of uterine contractions in any 20 minute window – Intermittent if occur <50% of uterine contractions in any 20 minute window – Unknown the predictive value of grading systems that utilize the depth of the deceleration

Fetal Heart Rate Categorization

• Three-tier system

– At a specific point in time – the FHT may move back and forth over time – Limited management discussion – Cannot predict cerebral palsy

Strongly predictive of normal acid-base status

NORMAL

ABNORMAL INDETERMINATE

Predictive of abnormal fetal acid-base status

Other Important Notes…

• FHTs need to be interpreted in the clinical

context

• 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

absence of fetal metabolic acidemia

– Minimal, absent or marked unclear

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Fetal Pulse Oximetry

• 2000 FDA approved a fetal pulse oximetry

system to use as an adjunct to EFM

– Sensor was placed through the cervix alongside the fetal face to measure fetal

• xygen saturation.

– Early studies showed some correlation between fetal metabolic acidosis and fetal saturation readings in the setting of a non- reassuring FHT.

5341 nulliparous women in early labor were randomized to open

• r masked fetal pulse oximetry.

2014 Cochrane Collaboration

• Fetal Pulse Oximetry did not reduce the
• verall Cesarean section rate
• A better method than pulse oximetry is

required to enhance the overall evaluation

• f fetal well-being in labour.

ST Segment Analysis (STAN)

• Approved by the FDA in 2005 but used in

Europe for two decades

• Standard cardiotocography (CTG) with

concurrent assessment of the fetal ECG.

– Normal ST waveform is horizontal or upward sloping – Normal T-wave has a constant amplitude – Changes in the waveforms may reflects fetal hypoxia

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11,108 term women in early to active labor with a singleton gestation were randomized to open or masked ECG ST-Segment analysis

2015

No difference in Cesarean delivery or

• perative

delivery

ST Segment Analysis (STAN)

• 2015 Cochrane Review Fetal ECG for

Fetal Monitoring During Labor

– Over 27,000 women from 7 trials

• No difference in Cesarean rate, severe fetal

acidosis or neonatal encephalopathy, no decrease in low 5 minute Apgar score

• Fewer fetal scalp samples and operative vaginal

deliveries (marginal)

• Several studies since this time have had

similar findings.

The Pros and Cons of EFM

• Screening test with poor positive

predictive value, esp. in low risk women

• No randomized clinical trials other than a

comparison to IA

– Increased Cesarean delivery rates – Increased operative delivery rates – Did not reduce perinatal mortality – Did not reduce the risk of cerebral palsy – Did decrease risk of neonatal seizures

• High intra- and intervariability

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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