Cardiotocography

1

Presented ByNirsuba Gurung

MN,Women Health and Development

05/01/2023

05/01/2023 2

Cardiocotography• Cardiotocography (CTG) is a

continuous electronic record of the fetal’s heart rate obtained via an ultrasound transducer placed on the mother’s abdomen

• It is sometimes referred to as ‘electronic fetal monitoring’ (EFM)

05/01/2023 3

CTG Contd…..• The machine used to perform the

monitoring is called a cardiotocograph, more commonly known as an electronic fetal monitor (EFM)

05/01/2023 4

Invention • The invasive fetal monitoring

was invented by Doctors Alan Bradfield, Orvan Hess and Edward Hon.

• A refined (antepartal, non-invasive, beat-to-beat) version (cardiotocograph) was later developed for Hewlett Packard by Dr. Konrad Hammacher.05/01/2023 5

Purpose• To record FHS continuously

• To check uterine activity

• To detect any fetal distress

• To gain information about rate, rhythm of the fetal heart rate and fetal movement

Indications for the use of

continuous EFM

905/01/2023

Indication Continuous EFM should be offered and recommended for high-riskpregnancies where there is an increased risk of perinatal death,cerebral palsy or neonatal encephalopathy.

Continuous EFM should be used where oxytocin is being used forinduction or augmentation of labour.

1005/01/2023

ADMISSION CTG Current evidence does not

support the use of the admission CTG in low-risk pregnancy and it is therefore not recommended

1105/01/2023

High-Risk IndicationsMaternal medical illness

Gestational diabetes Hypertension Asthma

Obstetric complicationsMultiple gestationPost-date gestationPrevious cesarean sectionIntrauterine growth restriction

OligohydramniosPremature rupture of the membranesCongenital malformationsThird-trimester bleedingOxytocin induction/augmentation of laborPreeclampsia

Meconium stained liquor 1205/01/2023

A Continuous EFM should be offered and recommended in pregnancies previously monitored with intermittent auscultation:

• if there is evidence on auscultation of a baseline less than 110 bpm or greater 160 bpm

• if there is evidence on auscultation of any decelerations

• if any intrapartum risk factors develop.

1305/01/2023

Methods

External Cardiotocography-

For continuous or intermittent monitoring of• The fetal heart rate and • The activity of the uterine muscle

• Placed two transducers on the mother's abdomen(one above the fetal heart and the other at the fundus).

External(Indirect) Monitoring

The tocodynamometer (“toco”) is placed over the uterine fundus. The

toco provides information that can be

used to monitor uterine

contractions.

The ultrasound device is

placed over the area of the fetal

back. This device

transmits information about the

FHR.

The pressure transducertransmits the pressure generatedby uterine contractions in mm Hg.•Each small vertical square is 5 mm Hg •Each small horizontal square is 10 seconds . •Each large horizontal square is 1 minute .

Pressure Transducer

Toco sensor

Ultrasound transducerThe ultrasound probe transmits thefetal heart rate in beats per minute. •Each small vertical square is 10 beats. •Each small horizontal square is 10 seconds .•Each large horizontal square is 1 minute .

05/01/2023 17

Ultrasound Probe

• Information from both the toco and the ultrasound device is transmitted to the electronic fetal monitor.

• The FHR is displayed in a digital display (as a blinking light), on the special monitor paper, and audibly (by adjusting a button on the monitor). The uterine contractions are displayed on the special monitor paper as well.

18

Internal Cardiotocography-

• Uses an electronic transducer connected directly to the fetal scalp through the cervical opening and is connected to the monitor.

• Internal monitoring provides a more accurate.

• Internal monitoring may be used when external monitoring of the fetal heart rate is inadequate.

• It need some degree of cervical dilatation.

Internal MonitoringCriteria for Internal Monitoring: Amniotic membranes must be ruptured

Cervix dilated 2 cm.Presentation must be cephalic Presenting part down against the cervix

• Spiral Electrode is placed on the fetal occiput which allows for more accurate continuous data than external monitoring.

• Also is not affected by mom or fetal movement as with external monitoring.

05/01/2023 21

Internal Monitoring

The spiral electrode is attached to the

fetal scalpWires that extend

from attached spiral electrode are

attached to a leg plate and then

attached to electronic fetal

monitor.

Procedure Equipments• Cardiotocograph• Transducer(2):Toco and cardio• Conduction gel or paste• Abdominal binder (two belts)• Monitor paper• Tissue paper

05/01/2023 23

Preparation for CTG• Determine the indication for fetal

monitoring• Explain the purpose, time required

for test• Instruct the women for empty the

bladder• Place the women in supine position• Uncover the abdomen

Procedure • Place the tocosensor on the fundus of

utreus and fix it with abdominal binder• Identify the presentation and position of

the fetus• Localize the FHS and fix it with abdominal

binder

Procedure • Assure the recording of FHS and

uterine contraction• Explain the mother to push the

bottom when she feel any movements

• Labeled the women’s name, I.P. number, date and time in CATAG graph

05/01/2023 27

Procedure • Turn off the monitor and replace• Read the CTG and immediately

notify the doctor ,if any abnormality seen

05/01/2023 28

Interpretation• Uterine activity (contractions)

• Baseline fetal heart rate (FHR)

• Baseline FHR variability

• Presence of accelerations

• Periodic or episodic decelerations

• Changes or trends of FHR patterns over time.

Uterine activity(contraction)

• Frequency- the amount of time between the start of one contraction to the start of the next contraction.

• Duration :The amount of time from the start of a contraction to the end of the same contraction

• Intensity (strongeness):a measure of how strong a contraction is. In early labour the contractions are weak, with amplitude of about 20 mm Hg and at the end of the first stage 60 mm Hg

Uterine activity(contraction)

• Resting Tone- a measure of how relaxed the uterus is between contraction(between 4-10 mm Hg)

• Interval- the amount of time between the end of one contraction to the beginning of the next contraction.

• Record the number of contractions present in a 10 minute period - e.g. 3 in 10

• Each big square is equal to 1 minute, so look how many contractions occurred in 10 squares

• Individual contractions are seen as peaks on the part of the CTG monitoring uterine activity

• assess contractions for duration and intensity

Baseline fetal heart rate

The mean level of the FHR when this is stable, excluding accelerations and decelerations. It is determined over a time period of 5 or 10 minutes and expressed in bpm.

3305/01/2023

– Normal Baseline FHR 110–160 bpm

– Moderate bradycardia 100–109 bpm

– Moderate tachycardia 161–180 bpm

– Abnormal bradycardia < 100 bpm– Abnormal tachycardia > 180 bpm3405/01/2023

Baseline Fetal Heart rate Normal Pattern

• Baseline FHR = 110 – 160 bpm

Baseline variability• Variability refers to the normal beat to beat changes in FHR.

• Normal variability is between 5-15 bpm.

• Variability can be measured by analysing a one-minute portion of the CTG by estimating the difference in beats per minute between the highest peak and lowest trough of fluctuation in a one-minute segment of the trace 37

Baseline variabilityThe fluctuations are visually quantities

as the amplitude of the peak-to-trough in bpm. Using this definition, the baseline FHR variability is categorized by the quantitated amplitude as:

• Absent- undetectable• Minimal- greater than undetectable,

but less than or equal to 5 bpm• Moderate- 6-25 bpm• Marked- greater than 25 bpm05/01/2023 38

3905/01/2023

FHR Variability

Absent variability = Amplitude range undetectable

Minimal = < 5 BPM

Moderate = 6 to 25 BPM

Marked = > 25 BPM

Accelerations• To be called an acceleration, the peak

must be greater than or equal to 15 bpm, and the acceleration must last greater than or equal to 15 seconds from the onset to return to baseline.

• Prolonged acceleration: is greater than or equal to 2 minutes but less than 10 minutes in duration.

• Before 32 weeks of gestation, accelerations are defined as having a peak greater than or equal to 10 bpm and a duration of greater than or equal to 10 seconds.

ACCELERATIONS

4505/01/2023

Deceleration

Decreases in fetal heart rate from the base line by at least 15b/m, lasting for at least 15 seconds.

DECCELERATIONS• EARLY : Head compression

• LATE : U-P Insufficiency

• VARIABLE : Cord compression Primary CNS

dysfn4805/01/2023

Early Deceleration• Early Deceleration: Early begin at

start of uterine contraction and end with conclusion of contraction. Early decelerations are not a sign of fetal problems.

• In most cases the onset, nadir(lowest point), and recovery of the deceleration are coincident with the beginning, peak, and ending of the contraction, respectively

EARLY

5005/01/2023

Early Decelerations

• Related to Head Compression

• Intervention– No intervention necessary. Just continue to

watch for any changes.

Early decelerations contd…

• Early decelerations are a benign( kind/ gentle) finding caused by a vasovagal response as a result of fetal head compression by the contraction.

• Pressure on the fetal skull alters the cerebral blood flow and this in turn stimulates the vagus nerve

Early Decelerations

Variable Deceleration

Variable Deceleration

• Variable decelerations are variable in duration, intensity, and timing

Variable decelerations

Abrupt(sudden)  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.

VARIABLE

5905/01/2023

Variable Decelerations• Related to cord compression

• Intervention–Reposition –Amnioinfusion

variable deceleration contd…• The umbilical vein is often occluded

first causing an acceleration in response

• Then the umbilical artery is occluded causing a subsequent rapid deceleration

• When pressure on the cord is reduced another acceleration occurs & then the baseline rate returns

• Accelerations before & after a variable deceleration are known as the “shoulders of deceleration”

• There presence indicates the foetus is not yet hypoxic & is adapting to the reduced blood flow.

Late Deceleration

Late Deceleration

Gradual decrease in FHR with onset of deceleration to nadir >30 seconds.

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

Late Decelerations• Related to decreased

uteroplacental perfusion

LATE

6805/01/2023

Late Deceleration • The fetal heart tones return to the

baseline AFTER end of contraction

Two varieties of late decelerations reflex and nonreflex.

• Reflex late decelerations: are those which occur in the presence of normal FHR variability

• Non-reflex late decelerations occur in association with diminished or absent FHR variability.  

• Reflex late decelerations are thought to be due to vagal stimulation by chemoreceptors in the head in response to low oxygen tension.

• The hypoxemia -----increased sympathetic stimulation ------- increased systemic vascular resistance. The response to this increased pressure is a vagally mediated decrease in heart rate.

• This dual reflexive response may explain the delay in the heart rate following a contraction.

• Reflex late decelerations are associated with normal FHR variability because CNS system is intact.

• Nonreflex late decelerations are associated with a greater degree of relative hypoxemia and result in hypoxic depression of the myocardium coupled with the previously described vagal response.

• In reflex late decelerations, variability was maintained because the fetus was able to compensate, shifting oxygenated blood to vital organs (e.g., the heart),

• But in nonreflex late decelerations, the fetus is unable to compensate. It is these late decelerations which are more typically associated with fetal acidosis, and they are more commonly associated with placental dysfunction rather than uterine hypoperfusion or hyperactivity.

05/01/2023 74

Late Decelerations

Management

• Place patient on side • Administer O2 by tight face mask • Discontinue oxytocin. • Correct any hypotension • IV hydration. • If hyperstimulation is present consider terbutaline

0.25 mg SC • If late decelerations persist for more than 30 minutes

despite the above maneuvers, fetal scalp pH is indicated.

• Scalp pH > 7.25 is reassuring, pH 7.2-7.25 may be repeated in 30 minutes.

• Deliver for pH < 7.2 or minimal baseline variability with late or prolonged decelerations and inability to obtain fetal scalp pH

These maneuvers are primarily intended to alleviate "reflex" lates.

Prolonged DecelerationA prolonged deceleration is present when there is a visually apparent decrease in FHR from the baseline that is greater than or equal to 15 bpm, lasting greater than or equal to 2 minutes, but less than 10 minutes.

• If it lasts between 2-3 minutes it is classed as Non-Reasurring

• If it lasts longer than 3 minutes it is immediately classed as Abnormal

• Action must be taken quickly – e.g. Foetal blood sampling / emergency C-section

Prolonged Deceleration:

A deceleration that lasts greater than or equal to 10 minutes is a baseline change.

8005/01/2023

Categorisation of fetal heart rate traces

Category Definition

Normal All four reassuring

Suspicious 1 non-reassuring Rest reassuring

Pathological 2 or more non-reassuring 1 or more abnormal

8105/01/2023

SPECIAL PATTERNS

8205/01/2023

Sinusoidal patternA regular oscillation of the baseline long-term variability resembling a sine wave. This smooth, undulating pattern, lasting at least 10 minutes, has a relatively fixed period of 3–5 cycles per minute and an amplitude of 5–15 bpm above and below the baseline. Baseline variability is absent

Associated with - Severe chronic fetal anaemia Severe hypoxia & acidosis

8305/01/2023

SINUSOIDAL

8405/01/2023

PSEUDOSINUSOIDAL

8505/01/2023

SOME INTERESTING

CASES8605/01/2023

ACCELERATION OR DECCELERATION ???

8705/01/2023

BASELINE BRADYCARDIA WITH ACCELERATIONS

8805/01/2023

HALVING PHENOMENON

8905/01/2023

EXCESSIVE VARIABILITY???

9005/01/2023

GESTATIONAL DM ; NST ; 8:30am

9105/01/2023

GDM ; CST ; 12 noon

9205/01/2023

05/01/2023 93

References • Dutta, D.C. (2004).Text book of

Obstetrics. Sixth edition, New Central book agency

• Arias, F. Daftary, S.N. & Bhide, A. G.(2013). Practical guide to high risk pregnancy and delivery. Third edition, Elsiever

•

05/01/2023 94Nirsuba Gurung MN 1st year

• The Royal Australian and New Zealand College of Obstetricians and Gynaecologists (2006) Intrapartum Fetal Surveillance Clinical Guidelines.

• Baker L, Beaves M, Trickey D and Wallace E. 2009. Fetal Surveillance: A Practical Guide. Southern Health and RANZCOG

05/01/2023 95

Thank you

9605/01/2023