Fetal cardiotocography CTG

Dr Isameldin Elamin MD DOWH MBBS

Assistant Professor

Obstetrics & Gynaecology

By the end of this lectures Student should be able: To recognize different part of CTG. To describe how CTG works. To discuss the maternal risks which need

electronic fetal monitoring. To read and interpret the CTG.

Objectives

Cardiotocography (CTG) is a technical means of recording (-graphy) the fetal heartbeat (cardio-) and the uterine contractions (-toco-) during pregnancy.

The machine used to perform the monitoring is called a Cardiotocograph, more commonly known as an Electronic Fetal Monitor (EFM).

Introduction

Changes in FH rate patterns occur in

response to changes in O2, CO2, hydrogen

ions and arterial pressure

These changes are mediated via the vagus

nerve, chemoreceptors & carotid body

baroreceptors

Pathophysiology of FH rate changes

It is difficult to measure fetal oxygenation and

pH continuously

FH rate patterns only allow indirect

assessment of fetal acid-base balance.

Fetal scalp sampling is required to confirm

whether the fetus is hypoxic…

Pathophysiology of FH rate changes

The heart rate of the fetus is calculated

using a Doppler ultrasound transducer.

signals detected are  cardiac movement.

what is actually measured is the time

interval between cardiac cycles. this is converted

 to heart rate.

Principle of CTG

CTG monitors: Fetal heart rate (FHR). uterine contractions.

prints on a two-channel strip chart recorder.

Principle of CTG…CONT.

CTG obtained by:

external transducers that are placed on the

maternal abdomen.

Internal monitoring by:

spiral electrode onto the fetal scalp.

plastic catheter

transcervically to monitor uterine contractions.

Principle of CTG…CONT.

2 electrode one for FHROne for uterine contraction

for FHR on lower abdomenfor uterine contraction on upper abdomen

CTG machine and paper

CTG probes Feto and toco

Setting CTG machine speed 1cm or 2 or 3 cm per minute

Internal monitoring

CTG trace showing Uterine contraction and fetal heart rate

Perinatal outcomes

50% reduction in neonatal seizures … but no difference in incidence of: - long-term neurological handicap - or perinatal mortality.Obstetric outcomes

66% increase in Caesarean section rate16% increase in instrumental delivery

CTG: Aim & out comes

CTG Should be reserved for high risk pregnancies.

(CTG) is the accepted standard for: intra-partum fetal monitoring in women with

additional risk factors.

Non-sterss test (NST) for fetal monitoring in

women not in labour.

CTG: Aim & out comes

Fetal risks:Intrauterine growth restrictionOligohydramniosAbnormal Doppler velocimetryPreterm labourMultiple pregnancyBreech presentationRhesus iso-immunisation

Risk factors

Maternal risks: Previous Caesarean section Pre-eclampsia Pregnancy >42 weeks Prolonged ROM >24 hours Diabetes Antepartum haemorrhage Significant medical condition – eg cardiac

Risk factors CONT.

Meconium stained liquor. Abnormal FHR on auscultation

Tachycardia Decelerations.

Maternal pyrexia 38°C once or 37.5°C on 2 occasions 2 hours apart

Fresh bleeding in labour Oxytocin augmentation

Changing from low risk to high risk

Many school for interpretation of CTG NICE, ACOG, ALSO, others All Through the following features: Basal heart rate (BHR). Beat to beat variability. Accelerations. Decelerations. Uterine contractions.

CTG reading and interpretation

Letters to make reading CTG more easy.

Determine Risk Assess degree of “clinical risk” in relation to perinatal

outcomes

Low

Medium

High

DRCBRAVADO

Uterine Contraction

BASE LINE HEART RATE

ACCELERATIONS

VARIABILITY

DECELERATIONS

OVER ALL ASSESSMENT

DRCBRAVADO….cont.

Baseline Fetal Heart Rate

Must be >15 bpm and >15 sec above baseline Should be >2 per 15 min period Always reassuring when present May not occur when fetus is “sleeping” Should occur in response to fetal movements or

fetal stimulation Non reactive periods usually do not exceed 45

min (>90 min and no accelerations is worrying)

Accelerations

Accelerations

It is the most important feature of any CTG

Is a reflection of competing acceleratory and

decelerating CNS influences on the fetal heart

And therefore represents the best measure of

CNS oxygenation, so its absent may indicate CNS

hypoxia

Variability

Absent – undetectable Minimal less than or equal to 5bpm Moderate 6 to 25 bpm Marked greater than 25 bpm Will be affected by drugs and fetal sleeping

cycles Will be reduced in the pre term fetus and

congenital heart abnormalities

Variability…CONT.

variability

Reduced Normal

Variability

Early: mirrors the contractionTypically occurs as the head enters the

pelvis and is compressed, i.e. it is a vagal response

Late: Follows every contraction and exhibits a slow return to baseline

Uncommon, the response of a hypoxic myocardium

Uteroplacental insufficiency

Decelerations

Variable: Show no relationship to contractions

Variable shape, onset and durationUmbilical cord compression

In practice many decelerations are MIXED

CONT..

Early deceleration

Early Deceleration

Associated with fetal compromise (hypoxia) but only in 50-60% of cases

Ominous if associated with:- fresh particulate meconium- ‘high-risk’ clinical situation

Ominous if:- ‘lag-time’ (peak to trough)- deceleration is slow to recoverBeware of SHALLOW, DELAYED decelerations

Late Decelerations

Late Decelerations

Late Decelerations

• Begin after onset of contraction

• Nadir (or trough) after peak of contraction

• Return to baseline after end of contraction

Late Decelerations

Early vs. late decelerations

Most decelerations in labour are variableCan reflect cord compression‘Variable’ in shape, depth and/or onsetUsually benign but …. if late or deep may

imply cord prolapsed or hypoxia ‘Shoulders’ before and/or after ( )

are amore benign featureNeed to assess the frequency and duration

Variable Decelerations

Variable decelerations

Variable decelerations

Smooth undulating, sine wave pattern Defined by an amplitude of 10bpm in cycle of two

to five per minute, lasting at least two minutes. May be a terminal pattern -severe hypoxia Associated with severe fetal anaemia, hydrops

and fetomaternal haemorrhage. False sinusoidal pattern not uncommon,

particularly if intermittent and with normal variability

In a true sinusoidal pattern variability is absent

Sinusoidal pattern

Sinusoidal pattern

Sinusoidal pattern

Prolonged deceleration

CTG- Twins

CTG- Late deceleration+ decreased variabilityexample:

Frequency = no. in 10 minutesDuration of each contractionInterval = between end of one and starting of the next contractionMore than 5/10 min= tachysystoleIntensity- can not be directly measured by external CTG

Uterine contractions

Cord compression=variable deceleration. Head compression=early deceleration. Placental insufficiency= late deceleration

Remember

CTG Interpretation

No decision on the basis of (CTG) findings alone.

Take into account: risk factors. woman. unborn baby progress of labour.

Overall care

Care remains on the woman rather than the CTG trace.

Remain with the woman at all times.

Assessment of woman and baby hourly, or more

frequently if there are concerns.

Assess and document all 4 features. Not possible to categorise every CTG trace. Accelerations is a sign that the baby is healthy. If fetal blood sample cannot be obtained, but

results in accelerations, decide according to clinical circumstances and in discussion with the woman.

Principles for CTG interpretation

Baseline FHR (beats/ minute). Baseline variability (beats/ minute). Decelerations. Acceleration

CTG Features

Normal/ reassuring. Non-reassuring. Abnormal.

Description of Features

CTG is normal/reassuring. healthy fetus CTG is non-reassuring. increased risk of fetal acidosis Suggest conservative measures.

CTG Categories

CTG is abnormal more likely associated with fetal acidosis

indicate conservative measures Further testing. CTG is abnormal needs urgent intervention. very likely to be associated with current

fetal acidosis

100-160

normal/reassuring.

161–180 Non-

reassuring.

Above 180 or below 100. Abnormal.

Baseline FHR (beats/ minute)

5 or more. normal/reassuring.

less than 5 for 30–90 minutes. Non-

reassuring.

Less than 5 for over 90 minutes. Abnormal.

Baseline variability (beats/minute).

Normal/reassuring. None or early deceleration.

Decelerations

Non-reassuring:

Variable decelerations:

dropping = < 60 beats for 60 seconds or

less.

over 90 minutes

over 50% of contractions

deceleration

Variable decelerations:

more than 60 beats

or taking over 60 seconds.

present for up to 30 minutes

over 50% of contractions

Or Late decelerations: present for up to 30 minutes occurring with over 50% of contractions

Abnormal deceleration: Non-reassuring variable decelerations after conservative measures for 30 minutes. with over 50% of contractions.

Late decelerations for over 30 minutes not improve with conservative measures. with over 50% of contractions.

Bradycardia or a single prolonged deceleration lasting 3 minutes or more

CTG is normal/reassuring: All 3 features are normal/reassuring.

CTG is non-reassuring and suggest need conservative measures:

1 non-reassuring+2 normal/reassuring features

Interpretation of CTG or CTG categories

CTG is abnormal and indicate need for

conservative measures and further testing

1 abnormal Feature

OR 2 non-reassuring features

CTG is abnormal and indicate needs for urgent

intervention:

Bradycardia.

a single prolonged deceleration with

baseline below 100 beats/minute, persisting

for 3 minutes or more

Continue CTG and normal care.

remove CTG after 20 minutes if normal and

no risk factors

If CTG is normal/reassuring:

If fetal heart rate is over 160 beats/minute check temperature and pulse give fluids and paracetamol.

Start 1 or more conservative measures: mobilise and left-lateral position intravenous fluids stopping oxytocin offering tocolysis.Inform midwife and obstetrician.

CTG is non-reassuring

If fetal heart rate is over 180 beats/minute check temperature and pulse give fluids and paracetamol.

Start 1 or more conservative measures: mobilise left-lateral position intravenous fluids stopping oxytocin offering tocolysis. Inform midwife and obstetrician

CTG is abnormal + conservative measures +testing

Offer FBS after conservative measures. expedite birth if: FBS cannot be obtained no accelerations. Take action sooner than 30 minutes if: late decelerations + tachycardia +reduced

variability. Inform and discuss with the consultant if: FBS result is abnormal. FBS cannot be obtained third FBS is thought to be needed.

Start conservative measures. Inform midwife and obstetrician Urgently seek obstetric help Make preparations for urgent birth Expedite birth if persists for 9 minutes If heart rate recovers before 9 minutes, reassess

decision to expedite birth in discussion with the woman.

CTG is abnormal + urgent intervention

Classification of fetal blood sample results

Normal: offer repeat after 1 hour. Or sooner if additional non-reassuring or

abnormal features are seen. Borderline: offer repeat sampling in 30 minutes. Or sooner if additional non-reassuring or

abnormal features are seen.

Discuss with the consultant obstetrician if: a fetal blood sample cannot be obtained or a third fetal blood sample is thought to be

needed.

Description FHR variability Decelerations

Normal/reassuring 100–160 5 or more None or early

Nonreassuring 161–180 less than 5for 30–90 minutes

Variable decelaration:drop=<60 beats recover=<60 seconds for 90 minutes.Drop>60 beats recover>60 seconds up to 30 minutes.Late decelerations: present for up to 30 minutes

Abnormal Above 180orbelow 100

Less than 5for > 90 minutes

Still Non-reassuring for 30 minutes after conservative.Late decelerations >30 minutesnot improve with conservative.Bradycardia or deceleration =>3 minutes.

Conclusion CTG features

CTG Category Definition Interpretation Managementnormal/reassuring 3 features are

normal/reassuringHealthy fetus Remove CTG after 20

minutesNon-reassuring 1 non-reassuring

feature risk of fetal acidosis conservative measures

Abnormal : need for conservative measures AND further testing

1 abnormalOR2 non-reassuringfeatures

fetal acidosis more likely

conservative measuresFBS

Abnormal: need for urgent intervention

Bradycardiasingle prolonged deceleration for 3 minutes

current fetal acidosis

conservative measuresmake preparations for urgent birth

Conclusion CTG trace interpretation

Variable deceleration decreased variabilityCTG categary:Abnormal : need for conservative measures AND further testing FBS needed

BradycardiaCTG is abnormal and indicate needs for urgent intervention

Normal CTG with acceleration

variable decelerations with the V-shaped picture are a normal, reflex response to umbilical cord compression.

A preeclamptic patient at 33 weeks gestation with IUGR is undergoing induction of labor. The fetal heart rate tracing shows evidence of uteroplacental insufficiency and is nonreassuring.

A 23-year-old G1P0 at 42 weeks is undergoing induction of labor. She is receiving intravenous oxytocin. She complains that her contractions are very painful and seem to be continuous.

A patient at 41 weeks is undergoing NST. Her NST is reassuring.

Interpretations of CTG in uptodate: Category1=normal CTG Category2=nonreassuring. Category3=abnormal.

Uptodate and ACOG

intrapartum care: nice guideline cg190 (december 2014)

essentials of obstetrics & gynaecology hacker & moore, fifth edition

obstetrics by ten teachers 19 editions. http://www.uptodate.com.

Further reading

THANK YOU