Intrapartum Fetal Heart Rate Analysis 2009

Chukwuma I. Onyeije, M.D.
Atlanta Perinatal Associates
Clinical Associate Professor
Morehouse School of Medicine
http://maternalfetalmedicineblog.com
http://onyeije.net/present

Systemic Stimuli Transmitted via Placenta

Case Control Study:
More than 11,000
pregnancies studied.

FHR Characteristics associated with an increased risk of cerebral palsy
1. Multiple late decelerations
2. Decreased beat-to-beat variability of the heart rate

NELSON, and Colleagues. NEJM; 1996

The impairment of the delivery of oxygen to the brain and vital tissues during the progress of labor.

Hypertensive disorders
Preterm delivery
IUGR

Fetal Heart Rate evaluation has a high rate of false positives
Clinical management based soley on FHR to avoid asphyxia can result in more harm than good.

Many infants with cerebral palsy do not have have clinically apparent intrapartum abnormalities
Is there a way to improve FHR interpretation to improve perinatal outcome?

Macones GA, Hankins GD, Spong CY, Hauth J, Moore T. The 2008 National Institute of Child Health and Human Development workshop report on electronic fetal monitoring: update on definitions, interpretation, and research guidelines. Obstet Gynecol 2008;112:661–6.

Review and update definitions of FHR patterns
Evaluate existing classification systems for FHR
Make recommendations for research priorities

BACKGROUND CLINICAL INFORMATION
NATURE / PRESENCE OF CONTRACTIONS
BASELINE FHR
FHR VARIABILITY
PRESENCE OF ACCELERATIONS
PRESENCE OF DECELERATIONS
CHANGES IN FHR OVERTIME.

Number of contractions in a 10 minute window averaged over a 30 minute window.

FHR: PATIENT A
5 ctx per 10 min
4 ctx per 10 min
6 ctx per 10 min
TOTAL =15 ctx in 30 min
ANSWER: 15 ∕ 3 ═
5 ctx per 10 min
FHR: PATIENT B
2 ctx per 10 min
0 ctx per 10 min
4 ctx per 10 min
TOTAL =6 ctx in 30 min
ANSWER: 6 ∕ 3 ═
2 ctx per 10 min

ACTIVITY CLASSIFICATION Contractions per 10 min Normal Activity Five or Less TACHYSYSTOLE More than 5 HYPERSTIMULATION No Longer Valid HYPERCONTRACTILITY No Longer Valid

DURATION of contractions
INTENSITY of contractions
RELAXATION time between contractions
A normal fetus can withstand the stress of labor without suffering from hypoxia because sufficient oxygen exchange occurs during the interval between contractions.
A fetus whose oxygen supply is marginal cannot tolerate the stress of contractions and will become hypoxic.

Fetal heart rate
Meconium
Fetal blood sampling
Umbilical cord blood sampling
The Apgar scoring system
Contraction stress test
Ultrasonic assessment
Biophysical profile testing
Other Ways to Evaluate a Fetus During Labor

Auscultation of the fetal heart :by stethoscope or Doppler probe
Continuous Electronic fetal monitoring
External monitoring
Internal monitoring

Macones GA, Hankins GD, Spong CY, Hauth J, Moore T. The 2008 National Institute of Child Health and Human Development workshop report on electronic fetal monitoring: update on definitions, interpretation, and research guidelines. Obstet Gynecol 2008;112:661–6.

Fetal Heart Rate (in beats per minute)
Rate Beats/min Normal 120-160 Tachycardia >160 Bradycardia <120

Baseline variability
Short-time variability /beat-to-beat variability : short-term variability reflects the interval between either successive fetal electrocardiogram signals or mechanical events of the cardiac cycle
Long-term variability :Long-term variability reflects the frequency and amplitude of change in the baseline rate

Normal short-time variability fluctuates between 5 and 25 bpm
Variability below 5 bpm is considered to be potentially abnormal
When associated with decelerations a variability of less than 5 beats/minutes usually indicates severe fetal distress

The normal long-term variability is 3 to 10 cycles per minute.
Variability is physiologically decreased during the state of quiet sleep of the fetus,which usually lasts for about 25 minutes until transition occurs to another state.

Short-time variability beat-to-beat variability Long-term variability

No change : The FHR maintains the same characteristics as in the preceding baseline FHR.

Acceleration : The FHR increases in response to uterine contractions. this is normal response.

Deceleration : The FHR decreases in response to uterine contractions. Decelerations may be early, late, variable or mixed . All except early decelerations are abnormal.

Baseline rate 110-160 bpm,
Moderate variability,
Absence of late, or variable decelerations,
Early decelerations and accelerations may or may not be present.

Baseline rate
Bradycardia WITHOUT absent baseline variability
Tachycardia
Baseline FHR variability
Minimal baseline variability
Absent baseline variability with no recurrent decelerations
Marked baseline variability
Accelerations
Absence of induced accelerations after fetal stimulation

Periodic or episodic decelerations
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”

Absent baseline FHR variability and any of the following:
Recurrent late decelerations
Recurrent variable decelerations
Bradycardia
Sinusoidal pattern

Early deceleration
(head compression):
Late deceleration
( uteroplacental insufficiency
Variable deceleration
(cord compression)
Combined or mixed patterns
Decreased beat-to-beat variability

Definition : The onset, maximum fall, and recovery of FHR is a mirror image of the onset, peak, and end of the uterine contraction.
Significance : This pattern is seen when engagement of the fetal head has occurred. Early decelerations are not thought to be associated with fetal distress.
Mechanism : The pressure on the fetal head leads to increased intracranial pressure that elicits a vagal response

Definition :
---onset
---maximal
---decrease
---recovery is shifted to the right in relation to the contraction .
Late Decelerations (Uteroplacental Insufficiency) onset recovery max

Significance :
The severity is graded by t he magnitude of the decrease and the nadir of the deceleration
Fetal hypoxia and acidosis are more pronounced with severe decelerations
Generally associated with low scalp blood PH values and high base deficits, indicating metabolic acidosis from anaerobic netabolism
Late deceleration (uteroplacental insufficiency)

Definition: This pattern has a variable time of onset and a variable form and may be nonrepetitive

Significance :
caused by umbilical cord compression. The severity is graded by their duration.

Partial or complete compression of the cord causes a sudden increase in blood pressure in the central circulation of the fetus.
The bradycardia is mediated via baroreceptors
Fetal blood gases indicate respiratory acidosis with a low PH and high CO 2. When cord compression has been prolonged, hypoxia is also present, showing a picture of combined respiratory and metabolic acidosis in fetal blood gases
Variable deceletation (cord compression)

A flat baseline can be the result of several conditions:
Fetal acidosis
Quiet sleep state
Maternal sedation with drugs
Decreased beat-to beat variability

A normal FHR pattern on the electronic monitor indicates a greater than 95% probability of fetal well-being
Abnormal patterns may occur, however, in the absence of fetal distress. The false-positive rate (i.e., good Apgar scores and normal fetal-acid-bade status in the presence of abnormal FHR patterns) is as high as 80 %
Electronic fetal monitoring is a screening rather than a diagnostic technique, because of the high false-positive rate

Clinical circumstance
Maternal condition
Stage of labor
Clinical Considerations for FHR Interpretation

A change in maternal position can relieves fetal pressure on the cord
100% oxygen by face mask to the mother
Oxytocic infusion should be discontinued
Elevating the presenting part by vaginal examination
Placing the mother in the trendelenburg position if the pattern is persistent
Use tocolytic agent to diminish uterine activity
What To Do for… Variable Decelerations

Aminioinfusion can decrease both the frequency and severity of variable decelerations
The benefit of aminioinfusion results in reduced cesarean deliveries for fetal distress and fewer low Apgar scores at birth without apparent maternal or fetal distress

The safest intervention to deliver the fetus with cord compression is often low or outlet forceps.
When progressive acidosis occurs , as determined by serial scalp blood PH determinations, cesarean section should be performed if vaginal delivery is not imminent
Prolonged deceleration requires
immediate intervention (FHR
falls to 60 to 90 bpm for
more than 2 minutes)

Need further evaluation because it may be assosiated with fetal acidosis
acoustic stimulation can be used to try to induce FHR-accelerations
A response of greater than 15 bpm lasting at least 15 seconds can ensures the absence of fetal acidosis
The chance of acidosis occurring in the fetus who fails to respond to such stimulation is about 50%
What To Do for… Nonreactive fetal heart rate tracings

Change the maternal position from supine to left or right lateral
Give oxygen by face mask, this can increase fetal Po 2 by 5 mmHg
Stop any oxytocic infusion
Inject intravenously a bolus of tocolytic drug to relieve uterine tetany.
Monitor maternal blood pressure
Operative delivery should be considered for fetal distress when fetal acidosis is present or when late decelerations are persistent in early labor and the cervix is insufficiently dilated
What To Do for… Late Decelerations

Prolonged periods of tachycardia are usually associated with elevated maternal temperature or an intrauterine infection, which should be ruled out.
The acid-base status is usually normal
In general, fetal tachycardia occurs to improve placental circulation when the fetus is stressed.
Not a reliable change of the fetal distress
What To Do for… Fetal Tachycardia

There is an unrealistic expectation that a nonreassuring FHR tracing is predictive of cerebral palsy.
The positive predictive value of a nonreassuring pattern to predict cerebral palsy is 0.14%.

Out of 1,000 fetuses with a nonreassuring FHR pattern, only one or two will develop cerebral palsy
The false positive rate of EFM for predicting cerebral palsy is extremely high, at greater than 99%.
Available data suggest that the use of FHR monitoring does not result in a reduction in cerebral palsy

The interpretation of FHR is more consistent when the tracing is normal
In retrospective reviews, the foreknowledge of neonatal outcome alters the reviewer’s impressions of the tracing.
Reinterpretation of the FHR tracing, if neonatal outcome is known, may not be reliable.

MEDICATION EFFECT Narcotics Decrease in variability Decrease in the frequency of accelerations Butorphanol (Stadol) Transient sinusoidal FHR pattern Slight increased mean heart rate Cocaine Decreased long-term variability

MEDICATION EFFECT Corticosteroids Decrease in FHR variability with beta-methasone but not dexamethasone, Abolishes diurnal fetal rhythm. Increased effect at greater than 29 weeks of gestation Magnesium sulfate Decreased short-term variability, Insignificant decrease in FHR.

MEDICATION EFFECT Terbutaline Increase in baseline FHR Increased incidence of fetal tachycardia Zidovudine No difference in the FHR

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Intrapartum Fetal Heart Rate Analysis 2009

by Chukwuma Onyeije on Dec 13, 2009

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Intrapartum Fetal Heart Rate Analysis 2009 — Presentation Transcript