Basics of CTG Dr G Shree Lakshmi MS, MRCOG Rangadore Memorial Hospital ,Bangalore

Learning objectives What? Why? When? How? Terminology-Features& classification Limitations Legal issues

Cardiotocography A continuous recording of the fetal heart rate and uterine activities by electronic system. Antepartum Intrapartum

It’s a mode of assessing fetal wellbeing in labour Aim of CTG It’s a mode of assessing fetal wellbeing in labour The basic principle of fetal intrapartum monitoring is to detect developing fetalhypoxia with the aim of preventing subsequent acidaemia and cell damage.

Why is it we need to known about fetal hypoxia? Fetal hypoxia is a major cause for perinatal death, neonatal morbidity and neurodevelopmental disability. It can lead to complex medico–legal consequences.  ITS MAINLY ACIDOSIS WHICH HARMS THE FETUS

Why hypoxia in labour? During labor, the fetus experiences episodes of reduced oxygen supply and even lower oxygen tension than the conditions in utero. Even during theuncomplicated labor, the fetus undergoes a number of repeated periods with reduced oxygen supply, caused by the uterine contractions and the consequent reduction in uterine and placental blood flow. These brief hypoxic episodes are usually well tolerated, as the fetus has several defense mechanisms helping it to cope with the impaired oxygenation if it is a low riskpregnancy

Screening for fetal hypoxia- Cases at risk Obstetric H/O – IUGR, APH, Post term, reduced FM, multiple pregnancy, breech Meconium stained fluid – reduced quantity Intrauterine infection Iatrogenic – use of oxytocin

Why CTG in low risk labours Labour augumentation & use of epidural in low risklabours convert them to high risk …… which needs CTG HENCE TO LEARN CTG???

By monitoring FHR in CTG- we trying to detect fetal hypoxia

HYPOXIA-FHR CHANGES?? The effect of hypoxia on the fetal brain is reflected on the changes in FHR pattern Brain stem centres influence acceleration of FHR with movement baseline variability is a reflection of the integrity of the autonomic nervous systems. These centres are sensitive to hypoxia, and changes in the FHR pattern may suggest hypoxia. Hypoxia is the most important cause of fetal heart abnormality and is potentially dangerous.

Fetal Hypoxaemia ≠ Hypoxia ≠ Asphyxia ≠ HIE/ CP Respiratory & metabolic acidosis

pH is a log scale of H+

pH is a log scale of H+

Types of Hypoxia Cardiotocography detects hypoxia Acute Chronic Subacute Evolving

How to do a CTG ?

Pre-requisites for EFM – Check machine The date and time clocks on the EFM machine should be correctly set Adequate paper Trace of atleast 20 min required to interpret Set paper speed to 1 cm/min Trace should be labeled with the mother’s name, date and hospital number

Pre-requisites for EFM – Maternal Check and note maternal pulse on trace Identify FH using Pinard/ steth / Hand-held doppler before connecting cardio- transducer If maternal /fetal tachycardia note temperature on trace.

Pre-requisites for EFM – Maternal Propped-up / semi-recumbent Left lateral Tilted to either side with a 45 deg wedge Never take a trace with mum flat on her back!!!

Document Any intrapartum events that may affect the FHR should be noted contemporaneously on the EFM trace, signed and the date and time noted (e.g. vaginal examination, ARM, fetal blood sample, siting of an epidural, loss of contact)

Interpretation- 4 features Baseline Variability Accelerations Decelerations DEFINITIONS?

Each of these features have been divided as Reaasuring Nonreassuring Abnormal

Baseline rate - Mean level of FHR (excluding accelerations and decelerations) Reassuring 110-160bpm Non-reassuring 100 to 109† OR 161 to 180 Abnormal Below 100 OR Above 180 Observed over 5-10 minutes Prematurity associated with higher FHR Trend in baseline and absolute value important

Tachycardia>160BPM Normal 00-160BPM Bradycardia<100BPM

Baseline variability The minor fluctuations on baseline FHR at 3-5 cycles p/m produces Baseline variability. Examine 1 min segment and estimate highest peak and lowest trough. Normal is more than or equal to 5 bpm.

Variability Normal 5 to 25 between contractions Non-reassuring Less than 5 for 30 to 50minutes OR More than 25 for 15 to 25minutes Abnormal Less than 5 for more than 50minutes OR More than 25 for more than 25minutes OR Sinusoidal pattern for more than 10mins

5 Beats above and 5 beats below 1 minute

EFM-Accelerations Accelerations- transient increase in FHR of 15 bpm or more lasting for 15 sec. Presence of FHR Accelerations have Good outcome. Absence of accelerations on an otherwise normal CTG remains unclear.

Accelerations Normal 2 accelerations in a 20 minute trace “reactive” Accelerations less frequent in active labour

15 beats 15 seconds

EFM- Decelerations Transient episodes of slowing of FHR more than 15bpm for more than 15 seconds

Decelerations 15 sec 15 beats

Types of decelerations Early Variable Late

Describing decelerations their timing in relation to the peaks of the contractions the duration of the individual decelerations whether or not the fetal heart rate returns to baseline how long they have been present for whether they occur with over 50% of contractions the presence or absence of a biphasic (W) shape the presence or absence of shouldering the presence or absence of reduced variability within the deceleration

Early decelerations Uniform Repetitive Onset early in contraction Return to baseline by end of contraction Require head compression

Lag time

Early Decelerations

Late decelerations Uniform, repetitive Slowing of FHR with onset mid-end of contraction Nadir >20secs post contraction peak End after contraction

Late Decelerations. Repetitive late decels increases risk of Umbilical artery acidosis and Apgar score of less than 7 at 5 mins and Increased risk of CP. 15bpm for 15 seconds less in non-accelerative reduced variability trace

42 weeks, P0, Reduced FM Em LSCS, pH 7.23, Normal apgars

Fig 4 Late Decelerations

Variable decelerations Variable and intermittent Rapid onset and recovery Time relationship to contractions variable May be isolated May resemble other decelerations

Concerning characteristics of variable decelerations lasting more than 60seconds; reduced baseline variability within the deceleration; failure to return to baseline; biphasic (W) shape; no shouldering.

Fig 5 Variable Decelerations

FEATURE DECELERATIONS REASSURING None or Early ,Variable decelerations with no concerning characteristics* for less than 90minutes NON REASSURING Variable decelerations with no concerning characteristics* for 90minutes or more OR Variable decelerations with any concerning characteristics* in up to 50% of contractions for 30 minutes or more OR Variable decelerations with any concerning characteristics* in over 50% of contractions for less than 30 minutes OR Late decelerations in over 50% of contractions for less than 30 minutes, with no maternal or fetal clinical risk factors such as vaginal bleeding or significant meconium ABNORMAL Variable decelerations with any concerning characteristics* in over 50% of contractions for 30minutes (or less if any maternal or fetal clinical risk factors [see above]) OR Late decelerations for 30minutes (or less if any maternal or fetal clinical risk factors) OR Acute bradycardia, or a single prolonged deceleration lasting 3minutes or more

Prolonged deceleration Abrupt fall in FHR lasting for at least 60 seconds

Prolonged deceleration Non-reassuring 60-180 seconds Abnormal >3 minutes

CLASSIFICATION OF CTG

Classification of CTG Features Reassuring Non- Reassuring Abnormal Baseline FHR 110 -160 bpm 100 to 109† OR 161 to 180 Below 100 OR Above 180 Baseline variability > 5 bpm to 25bpm Less than 5 for 30 to 50minutes OR More than 25 for 15 to 25minutes Less than 5 for more than 50minutes OR More than 25 for more than 25minutes OR Sinusoidal Acceleration Present

FEATURE DECELERATIONS REASSURING None or Early ,Variable decelerations with no concerning characteristics* for less than 90minutes NON REASSURING Variable decelerations with no concerning characteristics* for 90minutes or more OR Variable decelerations with any concerning characteristics* in up to 50% of contractions for 30 minutes or more OR Variable decelerations with any concerning characteristics* in over 50% of contractions for less than 30 minutes OR Late decelerations in over 50% of contractions for less than 30 minutes, with no maternal or fetal clinical risk factors such as vaginal bleeding or significant meconium ABNORMAL Variable decelerations with any concerning characteristics* in over 50% of contractions for 30minutes (or less if any maternal or fetal clinical risk factors [see above]) OR Late decelerations for 30minutes (or less if any maternal or fetal clinical risk factors) OR Acute bradycardia, or a single prolonged deceleration lasting 3minutes or more

Classification of CTG Traces NORMAL All 4 features reassuring SUSPICIOUS 1 non-reassuring 3 reassuring features ABNORMAL 2 or more non-reassuring or 1 or more abnormal

Rate-normal Variability-normal Deceleration-none Acceleration-yes Classification-Normal BLORE RCOG TRUST

SUSPICIOUS Rate-150bpm Variability-10bpm Deceleration-variable Acceleration-? SUSPICIOUS BLORE RCOG TRUST

Deceleration-late Abnormal BLORE RCOG TRUST

Management based on interpretation of CTG traces

Category Definition Management Normal All features are reassuring Continue CTG and usual care

Category Definition Management Suspicious 1 non-reassuring feature AND 2 reassuring features Correct any underlying causes, such as hypotension or uterine hyperstimulation Perform a full set of maternal observations Start 1or more conservative measures* Document a plan for reviewing the whole clinical picture and the CTG findings Talk to the woman and her birth companion(s) about what is happening

Category Definition Management Pathological 1 abnormal feature OR 2 non-reassuring features Exclude acute events (for example, cord prolapse, suspected placental abruption or suspected uterine rupture) Correct any underlying causes, such as hypotension or uterine hyperstimulation Start 1or more conservative measures* If the cardiotocograph trace is still pathological after implementing conservative measures: obtain a further review by an senior obstetrician offer digital fetal scalp stimulation and document the outcome If the cardiotocograph trace is still pathological after fetal scalp stimulation: consider fetal blood sampling consider expediting the birth take the woman's preferences into account

Need for urgent intervention Acute bradycardia, or a single prolonged deceleration for 3minutes or more Urgently seek obstetric help If there has been an acute event (for example, cord prolapse, suspected placental abruption or suspected uterine rupture), expedite the birth Correct any underlying causes, such as hypotension or uterine hyperstimulation Start 1or more conservative measures* Make preparations for an urgent birth Talk to the woman and her birth companion(s) about what is happening Expedite the birth if the acute bradycardia persists for 9minutes If the fetal heart rate recovers at any time up to 9minutes, reassess any decision to expedite the birth, in discussion with the woman

Conservative Measures Encourage the woman to mobilise or adopt an alternative position (and to avoid being supine); Offer intravenous fluids if the woman is hypotensive; Reduce contraction frequency by reducing or stopping oxytocin if it is being used And/or offering a tocolytic drug (a suggested regimen is subcutaneous terbutaline 0.25mg).

Can we detect hypoxia in time? Can we detect hypoxia reliably? STRENGHTS & WEAKNESS OF INTRAPARTUM SURVEILLANCE Can we detect hypoxia in time? Can we detect hypoxia reliably?

EFM- Facts ? Affordability Reliability of interpretation-50-75% are false positive Sensitive in detecting abnormalities of fetal heart rate (FHR) Specificity for detection of fetal hypoxia is low False positive Dx reduces with FBS. FBS 93% sensitivity, 6% false positive ? Affordability

Reliability of CTG Interpretation 50%-75% false positive False Positive Dx is reduced to 10% with FBS PH Vs lactate 39% Vs 2.3%(rr16.79) Negative predictive value high

Inter-Observer Variation 5 clinicians, 100 parturients •Traditional intrapartum evaluation: reassuring vs. nonreassuring •46% of these patients had an emergent C/S •2% had a fetal pH less than 7.0 •Study found poor inter-rater reliability and they could not predict which parturient had an emergency C/S or low pH! Chauhan SP, Klauser CK, Woodring TC, Sanderson M, Magann EF, Morrison JC. Intrapartum nonreassuring fetal heart tracing and prediction of adverse outcomes: Interobserver variability. Am J Obstet Gynecol. 2008;199(6):623.e1-e5.

Perinatal asphyxia Birth asphyxia that is severe enough to cause severe hypoxic ischaemic encephalopathy should have the following: profound umbilical artery metabolic acidaemia defined as a pH < 7.0 persistence of a low Apgar score < 3 for more than 5minutes abnormal neurological signs during the neonatal period evidence of hypoxic damage to other body systems such as cardiovascular, pulmonary, gastrointestinal, renal and haematological system ACOG 1992 International Cerebral palsy Task Force 1999

Cardiotocography (CTG) Facts Remains the predominant method of intrapartum fetal monitoring Main documentary evidence in medico-legal cases related to intrapartum hypoxia and birth asphyxia

Contributors To Adverse Perinatal Outcomes Inability to interpret traces failure to incorporate the clinical situation delay in taking appropriate action poor team working – communication lag

In Utero Diagnosis Of Fetal Hypoxia? Hypoxaemia -> Hypoxia-> Asphyxia Consider Clinical picture re-physiological reserve (IUGR,APH,PT, meconium etc.) Rate of progress of labour – parity, contractions, oxytocin, partogram Diagnosis of hypoxia > Asphyxia – additional methods pH, lactate Resuscitative measures> no improvement > delivery

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