Cardiotocography as a Test of Cardiotocography as a Test of Fetal Well BeingFetal Well Being

Max Brinsmead MB BS PhDMax Brinsmead MB BS PhDDecember 2014December 2014

The objective of CTG screening:The objective of CTG screening:

x = H ealthy0 = H ypoxic

x x x 0 x x x 0 x x x 0x x x 0 x x x 0 x x x 0x x x 0 x x x 0 x x x 0x x x 0 x x x 0 x x x 0

An ideal screening test:An ideal screening test:

x = H ealthy0 = H ypoxic

x x x x x x x x xx x x x x x x x xx x x x x x x x xx x x x x x x x x

0 0 00 0 00 0 00 0 0

x x x 0 x x x 0 x x x 0x x x 0 x x x 0 x x x 0x x x 0 x x x 0 x x x 0x x x 0 x x x 0 x x x 0

CTG as a screening testCTG as a screening test

x = H ealthy0 = H ypoxic

x x x 0 0 0x x x 0 0 0x x x 0 0 0x x x 0 0 0

x x x x x xx x x O x xx x x x x xx x x x x x

x x x 0 x x x 0 x x x 0x x x 0 x x x 0 x x x 0x x x 0 x x x 0 x x x 0x x x 0 x x x 0 x x x 0

CTG as a Screening TestCTG as a Screening Test

Positive predictive value Positive predictive value = the chance that = the chance that a screen positive individual will have the a screen positive individual will have the diseasedisease

For CTG this is never more than 50% For CTG this is never more than 50% i.e. at least 50% of the time it will be i.e. at least 50% of the time it will be

unnnecessarily alarming unnnecessarily alarming

A screening test is more likely to A screening test is more likely to be a true positive ifbe a true positive if

A screening test is more likely to A screening test is more likely to be a true positive ifbe a true positive if

It is positive in a high risk It is positive in a high risk groupgroup

So always consider the So always consider the clinical contextclinical context

And be prepared to back up And be prepared to back up with a diagnostic testwith a diagnostic test

Which, for the diagnosis of fetal Which, for the diagnosis of fetal hypoxia, is Scalp Blood pH or hypoxia, is Scalp Blood pH or

lactatelactate

Problems with Screening:Problems with Screening:

FALSE POSITIVESFALSE POSITIVES– And the resources required to deal with themAnd the resources required to deal with them

UNREALISTIC EXPECATATIONSUNREALISTIC EXPECATATIONS– i.e. misunderstanding about the sensitivity of i.e. misunderstanding about the sensitivity of

the testthe test

Meta analysis of RCTs of Meta analysis of RCTs of Intrapartum CTG monitoringIntrapartum CTG monitoring

12 Trials12 Trials In 10 centres in the US, Australia, Europe In 10 centres in the US, Australia, Europe

and Africaand Africa 58,855 women and 59,324 babies58,855 women and 59,324 babies Both high and low risk pregnanciesBoth high and low risk pregnancies Compared routine EFM with intermittent Compared routine EFM with intermittent

auscultationauscultation

Meta analysis ResultsMeta analysis Results

A significant decrease in:A significant decrease in:– rate of 1 minute Apgar scores less than 4 (RR = rate of 1 minute Apgar scores less than 4 (RR =

0.82 and CI 0.65 - 0.98)0.82 and CI 0.65 - 0.98)

– Neonatal seizures (RR=0.50 and CI 0.32 - 0.82)Neonatal seizures (RR=0.50 and CI 0.32 - 0.82)

Meta analysis ResultsMeta analysis Results

A significant increase in:A significant increase in:

The rate of intervention by Caesarean section The rate of intervention by Caesarean section and operative delivery (RR=1.23 and CI and operative delivery (RR=1.23 and CI 1.15 - 1.31)1.15 - 1.31)

Meta analysis ResultsMeta analysis Results

No effect on:No effect on:– rate of 1 min Apgar scores <7rate of 1 min Apgar scores <7

– rate of admissions to NICUrate of admissions to NICU

– Perinatal death ratePerinatal death rate

– 5 min Apgar scores5 min Apgar scores

– rate of Cerebral palsyrate of Cerebral palsy

But let us not throw out the baby But let us not throw out the baby withwith

The CTG’s dirty bathwater!The CTG’s dirty bathwater!

Because, as a screening test for Because, as a screening test for hypoxia,hypoxia,

IT IS CURRENTLY THE BEST IT IS CURRENTLY THE BEST TEST WE HAVETEST WE HAVE

Who should have Intrapartum CTG?Who should have Intrapartum CTG?

Patients who have increased risk for fetal Patients who have increased risk for fetal hypoxia or acidosishypoxia or acidosis– Identified by antenatal factorsIdentified by antenatal factors– Intrinsic fetal problemsIntrinsic fetal problems– Develop intrapartum problemsDevelop intrapartum problems

Antenatal RisksAntenatal Risks

Intrapartum indications for CTG?Intrapartum indications for CTG?

Suspected chorioamnionitis or temp >38Suspected chorioamnionitis or temp >3800 C C BP >160 systolic or 110 diastolicBP >160 systolic or 110 diastolic Oxytocin in useOxytocin in use Significant meconiumSignificant meconium Fresh vaginal bleedingFresh vaginal bleeding Non reassuring intermittent auscultationNon reassuring intermittent auscultation

– But remove after 20 min if normalBut remove after 20 min if normal

Intrapartum indications for CTG?Intrapartum indications for CTG?

Consider continuous CTG if 2 or more of Consider continuous CTG if 2 or more of the following occurthe following occur– BP >150 systolic or 100 diastolicBP >150 systolic or 100 diastolic– Delay in the 1Delay in the 1stst or 2 or 2ndnd stage stage– Light meconium stainingLight meconium staining

An Examination of CTG An Examination of CTG AbnormalitiesAbnormalities

What is ImportantWhat is Important

CTG FeaturesCTG Features

Baseline heart rateBaseline heart rate Decelerations - early, late and variableDecelerations - early, late and variable Short term variabilityShort term variability AccelerationsAccelerations

Reassuring CTGReassuring CTG

Baseline 110 – 160 bpmBaseline 110 – 160 bpm >5 bpm variability>5 bpm variability No decelerationsNo decelerations Accelerations presentAccelerations present(The absence of accelerations in an otherwise (The absence of accelerations in an otherwise

normal CTG is of uncertain significance)normal CTG is of uncertain significance)

Non Reassuring CTGNon Reassuring CTG

Baseline 100 - 109 or 161 - 180 bpmBaseline 100 - 109 or 161 - 180 bpm Variability <5 bpm for <40 but <90 minVariability <5 bpm for <40 but <90 min Variable decelerations <30 minVariable decelerations <30 min Single prolonged deceleration up to 3 min Single prolonged deceleration up to 3 min Decelerations in <50% contractions Decelerations in <50% contractions

Abnormal CTGAbnormal CTG

Baseline <100 or >180 bpmBaseline <100 or >180 bpm Variability <5 bpm for >90 minVariability <5 bpm for >90 min Decelerations with >50% of contractionsDecelerations with >50% of contractions Variable decelerations for >30 minVariable decelerations for >30 min Late decelerations for >30 minLate decelerations for >30 min Prolonged deceleration >3min or recursProlonged deceleration >3min or recurs Sinusoidal for >10 minSinusoidal for >10 min

DecelerationsDecelerations

Atypical Variable DecelerationAtypical Variable Deceleration

Slow return to baselineSlow return to baseline Secondary rise in baselineSecondary rise in baseline BiphasicBiphasic Loss of variability during decelerationLoss of variability during deceleration Continution baseline at a lower levelContinution baseline at a lower levelNB The 2014 NICE guidelines have NB The 2014 NICE guidelines have

dispensed with “atypical” and “typical”dispensed with “atypical” and “typical”

RCOG RecommendationsRCOG Recommendations

Settings on CTG machines should be Settings on CTG machines should be standardised, so that:standardised, so that:

• • Paper speed is set to 1 cm/minPaper speed is set to 1 cm/min • • Sensitivity displays are set to 20 Sensitivity displays are set to 20

bpm/cmbpm/cm • • FHR range displays of 50–210 FHR range displays of 50–210

bpm are used.bpm are used.

Categorisation of CTGsCategorisation of CTGs

Normal =A CTG where Normal =A CTG where all four all four features fall into the reassuring features fall into the reassuring categorycategory

Suspicious =a CTG with Suspicious =a CTG with one one non non reassuring featurereassuring feature

Pathological =a CTG with Pathological =a CTG with two or two or more more nonreassuring features or nonreassuring features or one or more abnormal featuresone or more abnormal features

RCOG and NICERCOG and NICE

RCOG and NICERCOG and NICE

Any Questions or Comments?Any Questions or Comments?

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