Fetal Heart Rate Monitoring

Daphne Christy P. RupisanOb-Gyne Resident

Fetal heart rate setting mechanism

• Simpatis:– In the myocardium– Ex: beta adrenegic, stress

• Parasimpatis– Between atrium and ventrikel– Asetilkolin-> Stimulating n.vagus-> heart rate↘– Atropin-> Inhibiting n.vagus-> heart rate ↗

• Baroreceptor– Aortic arch and carotid sinus– ↗ pressing-> stimulate n.vagus and n.glosofaringeus-> heart

rate ↘• Chemoreceptor

– Perifer: carotid and aortic corpus– Central: The medulla oblongata – O2 ↘ and CO2 ↗ heart rate ↗

• Hormonal – Stressasfiksiamed.adrenalepinefrin and

norepinefrinheart rate↗

Objectives

• To be able to interpret systematically CTG tracings.

• To be able to correlate clinically the CTG interpretations.

• To be able to recognizeberkisar non reassuring and ominous patterns on CTG tracings and apply appropriate management.

Interpretation of the fetal heart rate tracing

– follow a systematic approach• Baseline rate• Baseline fetal heart rate (FHR) variability• Presence of accelerations• Periodic or episodic decelerations• Frequency and intensity of uterine contractions• Changes or trends of FHR patterns over time

Baseline Fetal Heart Rate (FHR)

• heart rate during a 10 minute segment – rounded to the nearest 5 beat per minute

increment

Baseline Fetal Heart Rate (FHR)

• Normal baseline: between 110 and 160bpm

• Bradycardia :Mean FHR < 110 BPM

• Tachycardia: Mean FHR>160 BPM

• Baseline change: The decrease or increase in heart rate lasts for longer than 10 minutes.

Baseline FHR Variability

Baseline Variability

– An important index of cardiovascular function and appears to be regulated largely by the autonomic nervous system

Baseline FHR Variability

• ABSENT: amplitude range undetectable

Baseline FHR Variability

• MINIMAL: amplitude range detectable but <5 beats per minute

Baseline FHR Variability

• MODERATE: amplitude range 6-25 beats/min

Baseline FHR Variability

NICHD: Describing Accelerations

• Abrupt increase in FHR– Onset to peak < 30 seconds

• Peak: ≥ 15 bpm lasting 15 seconds from onset to return to baseline

• Prolonged acceleration: ≥ 2 min but < 10 min• Acceleration > 10 min = baseline change

AccelerationsAt 32 weeks AOG and beyondmelebihi

Before 32 weeks AOG

Peak 15 beats per minute or more above the baseline

10 beats per minute or more above the baseline

Acceleration Lasts 15 seconds or more but <2 minutes from the onset to the return to the previously determined baseline

Lasts 10 seconds or more, but < 2 minutes from the onset to the return to the previously determined baseline

Prolonged acceleration: Increase in heart rate lasts for 2 to < 10 minutes.

• REACTIVITY– An increase of 15 BPM

above baseline for 15 second duration (from baseline to baseline) twice in a 20 minute period.

– Presence of 2 acceleration in a 20 minute period

• Sinosoidal pattern– Visually apparent, smooth, sine wavelike undulating

pattern in FHR baseline with a cycle frequency of 3-5 per minute which persists for 20 minutes or more

• Sinusoidal pattern maybe observed with– Severe fetal anemia from Rh

isoimmunization– Feto-maternal hemorrhage– Twin-twin transfusion syndrome– Vasa previa w/ bleeding– Fetal intacranial hemorhage– Severe fetal asphyxia

Williams,23rd edition; Intrapartum Assessment

Decelerations

• Periodic – Not associated with uterine contractions

• Episodic– Associated with uterine contractions

Decelerations

• Early deceleration– Gradual decrease in

FHR with onset of deceleration to nadir >30 seconds

– nadir occurs with the peak of a contraction.

• Head compression – Causes vagal nerve activation as a result of dural

stimulation and that mediates fetal heart rate deceleration

Williams,23rd edition; Intrapartum Assessment

Decelerations

• Late Deceleration: – Onset of the

deceleration occursterjadi

after the beginning of the contraction, and the nadir of the deceleration occurs after the peak of the contraction.

Causes of late deceleration

• Any process that causes maternal hypotension (epidural analgesia)

• Excessive uterine activity• Placental dysfunction

– Maternal diseases• Hypertension• Diabetes• Collagen vascular disorder

Williams,23rd edition; Intrapartum Assessment

Decelerations• Variable:

– Abruptmendadak decrease in FHR of > 15 beats per minute measured from the most recently determined baseline rate.

– The onset of deceleration to nadir is less than 30 seconds.

– The deceleration lasts > 15 seconds and less than 2 minutes

Etiologies of variable deceleration

• Umbilical cord occlusion– it reflects either blood pressure changes

due to interruptiongangguan of umbilical flow or changes in oxygenation.

Williams,23rd edition; Intrapartum Assessment

American College of Obstetrician and Gynecologists (1995) has defined significant variable decelerations as those decreasing to less than 70 beats/min and lasting more than 60 seconds

Williams,23rd edition; Intrapartum Assessment

• Maternal hypotension

• Uterine hyperactivity

• Cord prolapse

• Cord compression*

Prolonged Decelerations

A decrease in FHR of ≥15 beats per minute measured from the most recently determined baseline rate. The deceleration lasts ≥ 2 minutes but < 10 minutes.

Causes:

• Rapid descent of fetal head

• Abruption

• Artifact (maternal heart rate)

• Maternal seizure

Uterine Contractions

• Normal: 5 or less contractions in 10 minutes averaged over a 30-minute window

POGS CPG on CS, November 2012

• Tachysystole– >5contractions in 10 minutes, averaged over

a 30-minute window– Always be qualified as to the presence or

absence of associated FHR decelerations– Applies to both spontaneous and stimulated

labor POGS CPG on CS, November 2012

Uterine Contractions

THREE TIERED CATEGORIZATION OF FHR INTERPRETATION

POGS CPG on Abnormal labor and Delivery, November 2009

Category I II III

Baseline FHR

110-160 beats per minute

Bradycardia not accompanied by absent baseline variability orTachycardia

Bradycardia

Baseline variability

Moderate • Minimal baseline variability• Absent baseline variability

with no recurrent decelerations

• Marked baseline variability

Absent

Decelerations

Late or variable decelerations: Absent

Early decelerations: present or absent

• Recurrent variable decelerations accompanied by minimal or moderate baseline variability

• Prolonged deceleration more than 2 minutes but less than 10 minutes

• Recurrent late decelerations with moderate baseline variability

• Variable decelerations with other characteristics such as slow return to baseline, overshoots, or “ shoulders”

• Recurrent late decelerations

• Recurrent variable decelerations

Accelerations

Present or absent • Absence of induced accelerations after fetal stimulation

Sinusoidal pattern

Evaluate:1. Cervical examination to determine umbilical cord

prolapse, rapid cervical dilatation or descent of fetal head.

2. Uterine contraction frequency and duration (r/o tachysystole)

3. Monitoring maternal blood pressure level for evidence of hypotension, especially in those with regional anesthesia

POGS CPG on Abnormal labor and Delivery, November 2009

Management for Category II or Category III tracing

Treat:1. Discontinue any labor stimulating agent.2. Change maternal position to left or right lateral

recumbent position, reducing compression of the vena cava and improving uteroplacental blood flow

3. If hypotensive, treat with volume expansion or with ephedrine or both or phenylephrine may be warranted

POGS CPG on Abnormal labor and Delivery, November 2009

Management for Category II or Category III tracing

Recommendations

– Detection of an abnormal FHR pattern (Cat III) is an indication for CS.

– Presence of 3 consecutive Cat II abnormal FHR patters, despite resuscitive measures is an Indication for CS.

POGS CPG ON CS, NOVEMBER 2012

• Optimal decision to delivery interval– If an emergency CS is warranted for an

abnormal FHR pattern or acute fetal compromise, it should be started as quickly as possible, ideally w/in 30 minutes.

POGS CPG ON CS, NOVEMBER 2012

LET US INTERPRET

Let us interpret!

Baseline FHR

Variability

Acceleration

Deceleration

Uterine contractions

Impression

• 1/17/14

145- 150

MODERATE

PRESENTABSENT

ABSENT REACTIVE NST

3/17/14 1 PMPU,32 weeks AOG CNIL IE: closed

Baseline FHRVariabilityAccelerationDecelerationUterine contractionsImpression

145-150

ABSENTABSENT

ABSENT uterine contractions every 2-3mins, 30-40 seconds, moderate

CATEGORY III

Baseline FHR

Variability

Acceleration

Deceleration

Uterine contractions

Impression

145-150

MINIMALPRESENT

PRESENTEvery 2-3 minutes mild to moderate , 50-60 secondsCATEGORY II, INDETERMINATE FOR MINIMAL VARIABILITY

Baseline FHRVariabilityAccelerationDecelerationUterine contractionsImpression

145-150

MODERATE

absentPRESENT

STRONG q 3-4min

CATEGORY II

Baseline FHRVariabilityAccelerationDecelerationUterine contractionsImpression

130-135

ABSENTABSENT

ABSENT

NONE

NON-REACTIVE NST

Baseline FHRVariabilityAccelerationDecelerationUterine contractionsImpression

150-155

ABSENTABSENT

PRESENT2 UTERINE CONTRACTIONS, 9 MINUTES APART MODERATE

CATEGORY III

Meeting the Objectives

To be able to interpret systematically CTG tracings.

To be able to correlate clinically the CTG interpretations.

To be able to recognize non reassuring and ominous patterns on CTG tracings and apply appropriate management.

“ It’s a lie to think you are not good enough... It’s a lie to think you’re not worth anything...”

Nick Vujicic, Life without limits