Antenatal Assessment ofAntenatal Assessment of Fetal Wellbeing Fetal Wellbeing

Dr Aisha SarfrazDr Aisha SarfrazSenior Registrar Obs & GynaeSenior Registrar Obs & Gynae

Civil Hospital, Bahawalpur, PakistanCivil Hospital, Bahawalpur, Pakistan

ANTENATAL ASSESSMENT OF FETAL WELL BEING

Prenatal care is designed to ensure the well being of both the expectant mother and the fetus

AIMSAIMS

• To identify fetuses at risk of intrauterine To identify fetuses at risk of intrauterine hypoxia so that a permanent injury or hypoxia so that a permanent injury or death can be prevented by timely death can be prevented by timely intervention.intervention.

• To identify healthy fetuses among those To identify healthy fetuses among those suspected to be in problem on clinical suspected to be in problem on clinical evaluation so that an unnecessary evaluation so that an unnecessary intervention may be avoided.intervention may be avoided.

Who?Who?• Conditions placing the fetus at risk for UPIConditions placing the fetus at risk for UPI

– Preeclampsia, chronic hypertension,Preeclampsia, chronic hypertension,– Collagen vascular disease, diabetes Collagen vascular disease, diabetes

mellitus, renal disease,mellitus, renal disease,– Fetal or maternal anemia, blood group Fetal or maternal anemia, blood group

sensitization,sensitization,– Hyperthyroidism, thrombophilia, cyanotic Hyperthyroidism, thrombophilia, cyanotic

heart disease,heart disease,– Postdate pregnancy,Postdate pregnancy,– Fetal growth restrictionFetal growth restriction

IDEAL TESTIDEAL TEST• allows intervention before fetal death or damage allows intervention before fetal death or damage

from asphyxia.from asphyxia.• Which has lower false positive and false negative Which has lower false positive and false negative

rates.rates.• FN antenatal test: incidence of fetal death within FN antenatal test: incidence of fetal death within

one week of a normal ante partum test.one week of a normal ante partum test.• FP test: abnormal test that prompts untimely FP test: abnormal test that prompts untimely

delivery but is not a/e evidence of fetal delivery but is not a/e evidence of fetal compromise (meconium stained amniotic fluid, compromise (meconium stained amniotic fluid, intrapartum fetal distress, low A/S and IUGR)intrapartum fetal distress, low A/S and IUGR)

None of currently available tests fulfill this criteriaNone of currently available tests fulfill this criteriaand reported FNr ranges from 0.4 to 1.9/1000 andand reported FNr ranges from 0.4 to 1.9/1000 andFPr from 30-90 %.FPr from 30-90 %.

TIMINGS OF PRENATAL TIMINGS OF PRENATAL ASSESMENTASSESMENT

Later half of pregnancyLater half of pregnancy

• after the age of viabilityafter the age of viability• 1st Trimester: USG1st Trimester: USG• 22ndnd Trimester: Biochemical test Trimester: Biochemical test

TESTS(2TESTS(2ndnd half of pregnancy) half of pregnancy)

1- 1- Screening TestsScreening Tests• Fetal movementsFetal movements• Symphysio fundal heightSymphysio fundal height

22 - - Specific testsSpecific tests• CTGCTG• USGUSG• BPPBPP• Doppler USGDoppler USG

Fetal movement countingFetal movement counting

• In presence of uteroplacental insufficiency In presence of uteroplacental insufficiency FM decrease for several days and stop FM decrease for several days and stop approx 24-48 hrs prior to fetal demise approx 24-48 hrs prior to fetal demise (attempt to save oxygen for more vital (attempt to save oxygen for more vital functions)functions)

• Cardiff “count to ten” : 10 movements in 12 Cardiff “count to ten” : 10 movements in 12 hours.hours.

• Kick chartsKick charts• Counting FM 2-3 times daily for 30 min Counting FM 2-3 times daily for 30 min

(further evaluation if <4 strong movements (further evaluation if <4 strong movements in 30 minin 30 min

AdvantagesAdvantages• Cheap, Continuous observation, Maternal Cheap, Continuous observation, Maternal

involvement, reported to perinatal mortalityinvolvement, reported to perinatal mortality

DisadvantagesDisadvantages• Rest activity behavior of fetus( maternal anxiety, Rest activity behavior of fetus( maternal anxiety,

frequency of hospital admission, use of CTG & frequency of hospital admission, use of CTG & C/S)C/S)

• Naturally quite fetus may take long time before 10 Naturally quite fetus may take long time before 10 movements are registered.movements are registered.

• Still births continue to occur with patients failing to Still births continue to occur with patients failing to report absence of noticeable FM.report absence of noticeable FM.

Symphysiofundal heightSymphysiofundal height

• Serial measurements are more effective than Serial measurements are more effective than single.single.

• SFH measurement after 24 wks has been taken SFH measurement after 24 wks has been taken to be equal in cms to the week of gestation to be equal in cms to the week of gestation ++2cm to 36 wks, and 3cms from 36-42 wks.2cm to 36 wks, and 3cms from 36-42 wks.

• Reduced SFH measurements correctly identify Reduced SFH measurements correctly identify only 25-50% of fetuses whose birth weight was only 25-50% of fetuses whose birth weight was <10<10 thth centile. centile.

Specif ic testsSpecif ic tests

1.1. CARDIOTOCOGRAPHYCARDIOTOCOGRAPHY(non stress test)(non stress test)

Antenatal CTG employs external(indirect methods Antenatal CTG employs external(indirect methods of monitoring of fetal heart rate). of monitoring of fetal heart rate). 3 techniques: 3 techniques:

a.a. Phonocardiography,Phonocardiography,b.b. fetal ECG, fetal ECG, c.c. Ultrasound fetal CTG : Ultrasound fetal CTG : Record of fetal cardiac Record of fetal cardiac

& uterine behavior on a paper is & uterine behavior on a paper is cardiotocographcardiotocograph and procedure is called and procedure is called cardiotocographycardiotocography..

INTERPRETATIONINTERPRETATION In antepartum CTG the study of uterine behavior has In antepartum CTG the study of uterine behavior has

little use only records Braxton hicks contractions.little use only records Braxton hicks contractions.Four variables of CTG:Four variables of CTG:

Baseline FHR Baseline FHR FHR variabilityFHR variability AccelerationAcceleration DecelerationDeceleration

All 4 variables are affected by oxygen deficiency, All 4 variables are affected by oxygen deficiency, making it a useful tool for diagnosis of antepartum making it a useful tool for diagnosis of antepartum fetal hypoxia. Fetal cardiac activity is controlled by fetal hypoxia. Fetal cardiac activity is controlled by both sympathetic & parasympathetic nervous system both sympathetic & parasympathetic nervous system which accelerates and lowers it respectively.which accelerates and lowers it respectively.

The fetal nervous system matures between 28-32 wks The fetal nervous system matures between 28-32 wks • Before 28 wks CTG is relatively featureless & has high Before 28 wks CTG is relatively featureless & has high

baseline FHR & reduced variability. With advancing baseline FHR & reduced variability. With advancing gestation FHR slows down & variability increases.gestation FHR slows down & variability increases.

• After 28 wks fetus develops cycles of quiet – active After 28 wks fetus develops cycles of quiet – active sleep lasting for 60-70 min. Quiet sleep phase usually sleep lasting for 60-70 min. Quiet sleep phase usually lasts for 20-30 min & characterized by absence of fetal lasts for 20-30 min & characterized by absence of fetal movements & CTG exhibits absence of accelerations movements & CTG exhibits absence of accelerations and low FHR variability.and low FHR variability.

CTG VARIABLESCTG VARIABLES

a.a. BASELINE FHRBASELINE FHR : : In late pregnancy b/w 110-150 bpmIn late pregnancy b/w 110-150 bpm

Effects of hypoxia:Effects of hypoxia:Acute hypoxia Acute hypoxia stimulates carotid artery CRsstimulates carotid artery CRs

stimulates ANS via carotid sinus nervestimulates ANS via carotid sinus nerveParasympathetic fetal bradycardiaParasympathetic fetal bradycardiaSympathetic peripheral vasoconstriction & Sympathetic peripheral vasoconstriction &

redistribution of cardiac output to brain, heart & redistribution of cardiac output to brain, heart & adrenals.adrenals.

Prolonged hypoxemia secretion of Prolonged hypoxemia secretion of catecholamines BP & FHR overcomes vagal catecholamines BP & FHR overcomes vagal bradycardia & baseline FHR is restored but bradycardia & baseline FHR is restored but vasoconstriction is maintained.vasoconstriction is maintained.

once oxygen delivery returns to normal vagal once oxygen delivery returns to normal vagal tone returns to normal unopposed catecholaminestone returns to normal unopposed catecholamines

rebound tachycardia. CAs Normal heart raterebound tachycardia. CAs Normal heart rate

Chronic HypoxiaChronic Hypoxia: constant rise in CAs maintains FHR : constant rise in CAs maintains FHR within normal limits by counteracting chronic vagal within normal limits by counteracting chronic vagal stimulation, the peripheral vasoconstriction is also stimulation, the peripheral vasoconstriction is also maintained. Variability & acceleration also returns to maintained. Variability & acceleration also returns to normal if chronic hypoxemia is not severe enough to normal if chronic hypoxemia is not severe enough to result in acidemia. Any acute insult over chronic hypoxia result in acidemia. Any acute insult over chronic hypoxia manifest as change in variability.manifest as change in variability.BRADYCARDIA(non hypoxic) BRADYCARDIA(non hypoxic) Prolonged Prolonged

pregnancy,pregnancy,fetal heart block, maternal hypothyroidism, SLE, CMVfetal heart block, maternal hypothyroidism, SLE, CMVhypoglycemia, hypothermia, b-blockers, local hypoglycemia, hypothermia, b-blockers, local

anestheticsanestheticsIdiopathic. Idiopathic. TACHYCARDIA(non hypoxic) TACHYCARDIA(non hypoxic) fetal prematurity,fetal prematurity,infections,anemia,maternal anxiety,hyperthyroidism and infections,anemia,maternal anxiety,hyperthyroidism and infections,beta sympatho & parasympathomometicsinfections,beta sympatho & parasympathomometics

b. b. FHR VARIABILITY FHR VARIABILITY : : Short Term Beat To Beat VariabilityShort Term Beat To Beat Variability:: variation of heart variation of heart rate in successive beats.rate in successive beats.Long Term VariabilityLong Term Variability:: 5-25bpm. Reduced during 5-25bpm. Reduced during hypoxia and quiet –sleep phase of baby, prematurity, hypoxia and quiet –sleep phase of baby, prematurity, maternal drugs like pethidine,diazepam & localmaternal drugs like pethidine,diazepam & localanesthetics.anesthetics. Reduced variability with decelerations should be takenReduced variability with decelerations should be takenseriously. seriously. It should be differentiated from sinusoidal FHRIt should be differentiated from sinusoidal FHRpattern(sign wave of fixed periodicity of 2-5 cycles/min,pattern(sign wave of fixed periodicity of 2-5 cycles/min,Amplitude of >25 bpm with loss of short term variability.Amplitude of >25 bpm with loss of short term variability.Seen in fetal anemia, fetal sickling.Seen in fetal anemia, fetal sickling.

c. c. Acceleration: Acceleration: Increase in FHR of >15bpm which Increase in FHR of >15bpm which persists for >15sec associated with fetal movements, persists for >15sec associated with fetal movements, external stimuli or uterine contractures.external stimuli or uterine contractures.Loss of accelerations is usually first sign of hypoxia but Loss of accelerations is usually first sign of hypoxia but also absent in quite sleep phase of fetus.also absent in quite sleep phase of fetus.d. d. Deceleration: Deceleration: A drop in FHR of >15bpm which persists for 10sec orA drop in FHR of >15bpm which persists for 10sec ormore.more.It’s a sign of hypoxia but also associated with maternalIt’s a sign of hypoxia but also associated with maternalsupine hypotension syndrome. An isolated decelerationsupine hypotension syndrome. An isolated decelerationwhen transient has little clinical significance whilewhen transient has little clinical significance whilerecurrent decelerations specially in absence of uterinerecurrent decelerations specially in absence of uterineactivity & with loss of beat to beat variability is sign ofactivity & with loss of beat to beat variability is sign ofpoor prognosis.poor prognosis.

REACTIVE CTG:REACTIVE CTG:1- Baseline FHR 110-150, 1- Baseline FHR 110-150, 2- variability 5-25bpm,2- variability 5-25bpm,3- 2 accelerations3- 2 accelerations4- No decelerations in 15-20min4- No decelerations in 15-20min

SEQUENCE OF EVENTS IN HYPOXIA:SEQUENCE OF EVENTS IN HYPOXIA:Absence of acceleration Loss of beat to beat Absence of acceleration Loss of beat to beat variability appearance of decelerations.variability appearance of decelerations.

STRESS TEST:STRESS TEST:1- Oxytocin challenge test1- Oxytocin challenge test2- Nipple stimulation test2- Nipple stimulation test3- Vibroacoustic stimulation 3- Vibroacoustic stimulation

Baseline tachycardia

Baseline bradycardia

normal beat to beat variability

Poor or absent variability

normal FHR accelerations with uterine contractions

DecelerationsDecelerations

• Decelerations- Decelerations- transient slowing of transient slowing of FHR below the FHR below the baseline level of baseline level of more than 15 bpm more than 15 bpm and lasting for 15 s and lasting for 15 s or more or more

Antenatal CTGAntenatal CTG

• Perinatal mortality: 6.2/1000Perinatal mortality: 6.2/1000• False positive rate: 50%False positive rate: 50%• False negative rate: 3.2 / 1000False negative rate: 3.2 / 1000

2- ULTRASOUND

• Quick, non-invasive procedure, easy interpretation

• Customised fetal growth charts (serial scans)• Liquor volume• Placental function

– Doppler study• Abnormal results correlate with increased risk

of stillbirth and neonatal morbidity in selected pregnancies

3- BIOPHYSICAL PROFILE3- BIOPHYSICAL PROFILE

• Described by Manning (1980)Described by Manning (1980)• The number of biophysical activities that The number of biophysical activities that

could be recorded increased with real time could be recorded increased with real time ultrasound: ultrasound: – Fetal movement (FM)Fetal movement (FM)– Fetal tone (FT)Fetal tone (FT)– Fetal breathing movements (FB)Fetal breathing movements (FB)– Amniotic fluid volume (AFV)Amniotic fluid volume (AFV)

Variables measuredVariables measured• CTG: CTG: reactive – as described earlier.reactive – as described earlier.• FBM: FBM: present - at least 1 episode of at present - at least 1 episode of at

least 60 seconds duration (within a 30min least 60 seconds duration (within a 30min period).period).

• FM: FM: present - at least 3 discrete episodes.present - at least 3 discrete episodes.• FT: FT: normal - at least 1 episode of normal - at least 1 episode of

extension of extremities or spine with return extension of extremities or spine with return to flexion.to flexion.

• AFV: AFV: normal – largest pocket of fluid normal – largest pocket of fluid greater than 1 cm in vertical diameter.greater than 1 cm in vertical diameter.

ScoringScoring

• Biophysical profile (BPP)Biophysical profile (BPP)– Each variable Each variable

• When normal: 2When normal: 2• When abnormal: 0When abnormal: 0

– Highest Score: 10, Lowest Score: 0Highest Score: 10, Lowest Score: 0– Accuracy improved by increasing the Accuracy improved by increasing the

number of variables assessed.number of variables assessed.– Overall false negative rate: 0.6/1000Overall false negative rate: 0.6/1000

SEQUENCE OF EVENTS IN HYPOXIASEQUENCE OF EVENTS IN HYPOXIA• Non-reactive CTGNon-reactive CTG• Absence of fetal breathing movementAbsence of fetal breathing movement• Reduction or loss of FMReduction or loss of FM• Loss of fetal toneLoss of fetal tone

MODIFICATIONMODIFICATION• CTG with AFV & FBMCTG with AFV & FBM• CTG with AFVCTG with AFV

4- DOPPLER ULTRASOUND4- DOPPLER ULTRASOUND

– Four fetal vesselsFour fetal vesselsUmbilical & middle cerebral arteryUmbilical & middle cerebral arteryThoracic aorta & ductus venosusThoracic aorta & ductus venosus

– In high risk pregnancies umbilical artery In high risk pregnancies umbilical artery doppler improves perinatal outcome.doppler improves perinatal outcome.

Doppler velocimetryDoppler velocimetry

• Uterine arteries – 24/40Uterine arteries – 24/40

UMBILICAL ARTERIAL DOPPLERUMBILICAL ARTERIAL DOPPLER

• Mid portion of cordMid portion of cord• In fetal quiescenceIn fetal quiescence• Use RI or PIUse RI or PI• Progressive fall in resistive indices Progressive fall in resistive indices

throughout normal pregnancythroughout normal pregnancy• Angle, sample volume importantAngle, sample volume important• Extremes of fetal heart rate will affect resultExtremes of fetal heart rate will affect result

S = peak systolic frequencies D = least diastolic frequencies

S-D/S = resistance or Pourcelot index

S-D/mean = Pulsatility index

(S/D = s d ratio, cannot describe AEDV )

These are gestation dependent the trend is important

NORMAL INDICESNORMAL INDICES• PI (S-D/mean) PI (S-D/mean) 0.8 – 1.10.8 – 1.1• RI(S-D/S)RI(S-D/S) at 30wks 0.8 – 0.98 at 30wks 0.8 – 0.98

at 35wks 0.75 – 0.95at 35wks 0.75 – 0.95 at 40wks 0.70 – 0.90at 40wks 0.70 – 0.90

• S/D ratio S/D ratio at 20wks 4.0 at 20wks 4.0 at 30wks 3.0at 30wks 3.0 at 40wks 2.0at 40wks 2.0

PI is preferred theoretically since it can still quantifyPI is preferred theoretically since it can still quantifyFVW in the absence of diastolic flow.FVW in the absence of diastolic flow.Clinically S/D ratio is commonly used while waveformsClinically S/D ratio is commonly used while waveformswith absent or reverse EDF are classified separately.with absent or reverse EDF are classified separately.

Use of Umbilical Arterial Doppler in Use of Umbilical Arterial Doppler in high risk pregnancy high risk pregnancy (preeclampsia and SGA)(preeclampsia and SGA)

• 30% reduction in perinatal death30% reduction in perinatal death• 40% reduction in admissions40% reduction in admissions∀↑↑ deliveries< 34 weeksdeliveries< 34 weeks• No differences in C/S or fetal distress No differences in C/S or fetal distress

in labourin labour

Cochrane review2000

Fetal growth restriction

Fetal “overgrowth”

Umbilical Doppler

FETAL VENOUS FETAL VENOUS DOPPLERDOPPLER

• Venous DopplerVenous Dopplera marker of fetal cardiac dysfunctiona marker of fetal cardiac dysfunctioninfluenced by fetal behavioural state esp FBMinfluenced by fetal behavioural state esp FBM

• Umbilical veinUmbilical vein non pulsatilenon pulsatilepulsatile decreased forward flow at end diastolepulsatile decreased forward flow at end diastole

• Ductus Venosus “M” shaped waveformDuctus Venosus “M” shaped waveformreversed velocities abnormalreversed velocities abnormalproposed usesproposed uses TTTSTTTS

aneuploidy screening 1aneuploidy screening 1stst T Tanaemiaanaemia

FETAL DOPPLER SUMMARYFETAL DOPPLER SUMMARY

• Umbilical artery well assessedUmbilical artery well assessed• Trend through gestation importantTrend through gestation important• Absent end diastolic velocities or reversed Absent end diastolic velocities or reversed

velocites always abnormalvelocites always abnormal• Doppler does not tell when delivery should Doppler does not tell when delivery should

occuroccur• Later in gestation fetus less tolerant of Later in gestation fetus less tolerant of

abnormal Dopplerabnormal Doppler• Pulsatile umbilical vein may be preterminalPulsatile umbilical vein may be preterminal

Uterine artery assessment

UTERINE ARTERY FLOW VELOCITY UTERINE ARTERY FLOW VELOCITY WAVEFORMSWAVEFORMS Upper panel normal waveformUpper panel normal waveform Lower panel abnormal with notching Lower panel abnormal with notching

IUGR SequenceIUGR SequenceAFI & UA Doppler changesAFI & UA Doppler changes

MCA changesMCA changes

Venous doppler changesVenous doppler changes

Reduction in short term variability (on comp CTG) &Reduction in short term variability (on comp CTG) &spontaneous decelerations on routine CTGspontaneous decelerations on routine CTG

Abnormal BPP ( breathing movements)Abnormal BPP ( breathing movements)

CONCLUSIONCONCLUSIONAbnormal screening testAbnormal screening test

Scan for growth measurementsScan for growth measurements

Within normal range &Within normal range & small measurementsmall measurementNo risk factors for UPINo risk factors for UPI

doppler studiesdoppler studiesReassurance & surveillance Reassurance & surveillance With FM & SFMWith FM & SFM Normal Normal AbnormalAbnormal

(UPI excluded)(UPI excluded)

SGASGA AdmissionAdmission monitoring with CTGmonitoring with CTG

Growth scanGrowth scan & BPP & BPP

THANK YOUTHANK YOU