CTG: Antepartum

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Aboubakr Elnashar Benha university Hospital, Egypt

Transcript of CTG: Antepartum

Aboubakr Elnashar

Benha university Hospital, Egypt

Aboubakr Elnashar

Patterns of foetal activity

1.Fetal breathing movements

2.Gross body movements

3.Fine motor movements

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During the last 10 w of pregnancy:

F. breathing movements: 30% of the time

Gross body movements: 10% of the time

At term:

Cycling between activity & quiescence: occurs

over a time span of 60 min

Activity is highest: in late evening

FHR variation: increases during fetal activity

f. body movements: FH acceleration

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Adaptations to hypoxia

Early

1.Reduced FHR reactivity

2.Absence of breathing movements

Late:

1. Reduced body movements and tone

2. Reduced liquor (renal hypoperfusion)

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The ideal test1. Quick

2. Easy to perform

3. Interpreted results that are reproducible.

4. Clearly identify the compromised fetus at a

stage at which intervention will improve the

outcome

5. Not give an abnormal result for a healthy fetus.

Unfortunately, this ideal test does not yet exist!

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I. Fetal movements counting (FMC)

II. FHR recording1.CTG

2.Non-Stress Test (NST)

3.Contraction StressTest (CST) or Oxytocin Challenge Test (OCT)

4.Nipple stimulation test5.Vibroacoustic stimulation (VAS)6.Computerized CTG

III. Biophysical Profile (BPP)

IV. Doppler

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FHR recording

1.CTG

2.NST

3.Contraction stress test

4.Nipple stimulation test

5.Acoustic stimulation test

6.Computerized CTG

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1. FHR tracings (CTG)METHOD

Simultaneous recordings are performed by 2

separate transducers:

1st for FHR

2nd for UC

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INTERPRETATION

1.Normal/Reassuring

Trace Baseline FHR: 110-150

b/m

Baseline variability: 10-

25 b/m

At least 2 accelerations

(>15 beats for> 15 sec in

20 min)

No decelerations.

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2. Suspicious/Equivocal Trace.

Baseline FHR: 150-170 b/m or 100-110 b/m

Reduced baseline variability (5-10 b/m for >40 m)

Absence of accelerations for >40 m

Sporadic deceleration of any type.

absence of

accelerations

diminished variability

late decelerations with

weak spontaneous

contractions. Aboubakr Elnashar

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Abnormal/Pathological Trace -

Baseline FHR: <100 b/m or > 170 b/m

No area of normal baseline variability

Silent Pattern (<5 b/m) for >40 min

Sinusoidal pattern (oscillation frequency = 2-5

cycles/min, amplitude of 5-15 b/m) for >40 m

No accelerations

Repeated

late,

prolonged (> 1 minute)

severe variable* (>40 b/m) decelerations. *decelerations vary in depth, vary in duration and vary in

timing relative to the uterine activity

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Tachycardia

Sinusoidal pattern

Late deceleration

normal baseline rate at 120

bpm,

absent baseline variability,

no accelerations

late decelerations

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variable fetal heart rate decelerations.

Reassuring shoulders (accelerations) are

obvious before and after each

deceleration.

baseline tachycardia

minimal variability.Aboubakr Elnashar

MANAGEMENT:

Normal/Reassuring Trace –

repeat and/or estimate AFI if considered necessary

acc to the cl situation and indication for testing.

Suspicious/Equivocal Trace –

Continue for up to 60 min {determine the

presence of f rest/activity cycles}.

Further evaluation acc to the cl situation e.g. fetal

acoustic stimulation, AFI, BPP, Doppler blood

velocity waveform.

Abnormal/Pathological Trace –

deliver if clinically appropriate.

Further evaluation/monitoring if not appropriate to

deliver. Aboubakr Elnashar

Advantages:

It is the most commonly

performed antenatal test for

fetal wellbeing.

Quick

Simple to perform

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2. The Non-Stress Test (NST) (Hammacher et al, 1960)

Idea:• FHR accelerations:

linked closely with f movements

{increased sympathetic output}.

• The long term variability:

{balance between sympathetic &

parasympathetic tone}

• The short term variability

(baseline or bandwidth variability)

{parasympathetic tone}.

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Steps:

1. left lateral recumbent position.

2. Place and adjust the external

tocodynamometer and US

transducer to obtain the best

possible tracing.

3. Instruct the patient to record f

movements on the monitor

tracing using the event marker.

4. Observe the EFM tracing until

the criteria for a reactive test are

met

(minimum of 20 min and maximum

of 60 min). Aboubakr Elnashar

In the event of lack of f movement, apply

stimulation e.g. fetal acoustic stimulator.

Record any relevant clinical information on the

EFM tracing e.g.

BP

T

P

loss of contact

changes in maternal position.

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Interpretation: Reactive:

2 accelerations of FHR in 20 min.

Each acceleration 15 beat & lasts 15 sec.

Non-reactive:

no accelerations in 40 min.

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•Reactive:

increase of FHR to >15 beats/min for

> 15 sec following fetal movements

Reactive

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Antenatal maternal glucose administration:

not to reduce non-reactive CTG (Cochrane , 2001)

Manual fetal manipulation:

not to reduce the incidence of non-reactive CTG. (Cochrane , 2001)

Reactive nonstress

reliable screening indicator of f wellbeing in

women presenting with perception of RFM in 3rd T

Abnormal pregnancy outcomes:

more common when initial CTG was non reactive(Daly et al, 2011)

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Disadvantages:1. Interpretation may be difficult &

poor agreement between experts

in assessing CTG

2. The predictive value of an abnormal

NST for perinatal morbidity &

mortality:<40% (Devoe et al, 1985)

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3. No significant effect on perinatal

outcome

(MA of 13 trials)

Trend towards increased perinatal

mortality (SR of 4 RCT)

(Cochrane library, 2001)

NST should not be relied upon as

the sole means of establishing f

wellbeing {Ia}

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3. The Contraction Stress Test (CST) or

Oxytocin Challenge Test (OCT)

1972: First introduced by Ray 1975: Freeman introduced the parameters of

contraction number and frequency to standardize

the test.

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Idea:It is a test of the

uteroplacental unit.

If fetal oxygenation is

marginal at rest, it will

transiently worsen with uterine

contractions: hypoxemia: late

decelerations.

If variable decelerations

were seen, one should

suspect oligohydramnios.Aboubakr Elnashar

Steps:Semi-fowlers position.

If the patient is not having spontaneous

contractions, pitocin is begun at 0.5-1.0 mU and

increased /15-20 minutes until 3C/10 min.

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Interpretation:Negative:

no decelerations with the 3 contractions in

the 10 minute window.

Positive:

late decelerations with 50% or more of the

contractions.

Suspicious:

intermittent late decelerations or severe

variable deceleration.

Unsatisfactory:

<3 contractions or hyperstimulation. Aboubakr Elnashar

•Non-reactive NST followed by CST:

mild late decelerations.

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CST: negative

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1. Negative

No deceleration

2. Positive

transient

decelerations

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Relative contraindications:

1. Preterm labor or certain patients at

high risk of preterm labor

2. Preterm membrane rupture

3. History of extensive uterine surgery

or classical cesarean delivery

4. Known placenta previa

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The role of this technique has yet to be established

it has been associated with reports of fetal

death in cases of unrecognized severe fetal

compromise [E].

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Sequence Of Events With Placental Insufficiency or Hypoxia

1. Positive CST= late deceleration in 50% of UC.

2. Non reactive NST= No HR acceleration

3. Cessation of fetal movement

4. Basal line tachycardia > 160 bpm

5. Basal line bradycardia <110 bpm

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5. VIBROACOUSTIC STIMULATION (VAS)Idea:

Vibroacoustic stimulator wakes a sleeping fetus:

changing its behavioral state.

How to perform:

Artificial larynxes that generate sound pressure

levels of approximately 80 to 100 decibels is

applied in two or three one-second bursts to the

maternal abdomen near the fetal head.

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Advantages:

1. Easy, relatively inexpensive way

to shorten testing times and reduce

the false-positive rates for NST &

biophysical profiles.

2. Fetuses that respond to VAS

with an acceleration on NST or a

startle response on FBP: very low

rates of death within one week of

the test.

3. Decrease the incidence of non-

reactive CTG and reducing the

testing time (The Cochrane Database of

Systematic Review, 2001)

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6. Computerized CTG

• To improve the objectivity of antenatal CTG

• The program unlike conventional CTG, allows

measurement of short term variability (STV).

• STV=variation measured in 3.75 s epochs.

• FHRV: better predictor of fetal compromise than the

acceleration or decelerations.

• Likelihood of metabolic acidaemia or IUFD can be

calculated according to the STV.

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Conventional Vs computerized CTG

1.Fewer additional fetal tests

2.Less time in testing.

3.The study was not large enough to

demonstrate any effect on perinatal

morbidity or mortality.

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III. The Biophysical Profile (BPP)

First described by Manning in 1980.

Idea:

Sequence of fetal deterioration

1. Late decelerations appear (CST)

2. Accelerations disappear (NST, BPP, CST)

3. F breathing stops (BPP)

4. F movement stops (BPP)

5. F tone absent (BPP)

6. A F decreases {chronic hypoxia: redistribution of cardiac

output away from the kidneys toward the brain}: AFV is a quick

evaluation of long term uteroplacental function as in the late

2nd and all the 3rd trimester {AF is essentially fetal urine}.

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OBSERVATION CRITERIA FOR PRESENT

CRITERIA FOR

NEGATIVE

F Tone 1 episode of flexion-extension-flexion in 30 min

No episodes of flexion-

extension-flexion in 30

minutes

F Movement 3 gross body movements in 30 min

Less than 3 gross body

movements in 30 minutes

F Breathing 1 episode of rhythmic breathing in 30 min

No episodes of rhythmic

breathing in 30 minutes

A FV One 2 centimeter pocket measured in two perpendicular planes

A pocket measuring

less than 2

centimeters

NST Reactive test Non-reactive test

Two points are given if the observation is present and zero points are given if it is

absent. Aboubakr Elnashar

Interpretation:8:

reassuring.

6:

equivocal: repeat within 24 h.

4 or less:

positive test: strongly suggests preparing

the patient for delivery.

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Modifications

1. BPP Manning (1990)

NST

AFV

Fetal breathing.

less cumbersome

results are just as predictive.

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2. Placental grading has been incorporated in the BPP to give an

overall score out of 12 rather than 10.

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3. The most powerful components: •AFI:

indicator of long term uteroplacental function

•NST:

short term indicator of fetal acid-base status.

assessment of fetal well-being using these two

tools alone may well be as effective as formal BPP

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Advantages:

1. In high-risk:

observational studies: effective

{good negative predictive value (99.9%)

i.e. fetal death is rare in women with a

normal FBP

rarely abnormal when Doppler findings

were normal}.

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2. In pre-labour rupture of the

membranes

{fetal breathing movements is reduced

in the presence of chorioamnionitis}

But sensitivity for abnormal BPP in the

presence of chorioamnionitis is

25%[B]: value of BPP is limited

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Disadvantages:

1. Difficult and time-consuming

2. False-positive rate: 70%: increased rates of unnecessary intervention.

3. Systematic review of five RCTs: failed to demonstrate any significant benefit of BPP on pregnancy outcome when compared to NST

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4. In low risk: cannot be recommended for routine monitoring

5. In high Risk: positive predictive value of 35% (observational study)

No enough evidence from RCTs

(Cochrane Systematic Review, 2000).: cannot be recommended for routine monitoring for primary surveillance in SGA

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Statistical Characteristics of Selected

Antepartum Fetal Tests

Characteristic NST CST BPP

Specificity Poor Average High

Specificity High High High

False-positive rate High High High

False-negative rate Low Low Average

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CONCLUSIONS

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1. CTG, must not form the sole basis for the

assessment of the fetus.

2. Computerized CTG may well be more effective

than standard CTG.

3. Formal assessment of the BPP does not

appear to hold any advantage over

assessment of liquor volume alone.

4. Where fetal growth restriction is suspected,

fetal biometry and assessment of umbilical

artery waveforms by Doppler ultrasonography

should be incorporated.

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