USS tests of fetal wellbeing

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USS tests of fetal wellbeing
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USS tests of fetal wellbeing

• Amniotic fluid assessment
• Biophysical profile
• Umbilical artery doppler
• Umbilical vein doppler
• (Uterine artery doppler)
• (Mean cerebral artery (MCA) doppler)

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Amniotic Fluid assessment

• Must not contain umbilical cord
• Deepest pocket
• lt2cm (oligo) or gt8cm (poly)
• AFI
• lt5th centile for gestational age (oligo)
• gt95th centile for gestational age (poly)
• lt5.1cm
• Subjective assessment by experienced operator

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Indications

• IUGR
• Reduced fetal movements
• Post dates pregnancy

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Biophysical ProfileHistory

• Screened out anomalies
• Alternative to Oxytocin Challenge Test
  Contraction Stress test
• Arbitrary Scoring-no reason for the weighting
  some components maybe more important than others
• Limited evidence to support its use
• Normal result useful for 24 hours

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Indications

• Post dates pregnancy
• IUGR
• Reduced fetal movements
• Maternal hypertension

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Parameters of Biophysical scoring

• CTG
• 2 accs with mvmts in 20mins
• FBMs
• gt1episode of 30s in 30min-not continuous
• Gross body/limb mvmts
• ?3 mvmts in 30mins-continuous
• Tone/posture
• 1 episode flexion-extension-flexion of
  limb,opening hand, mouth, trunk rotation
• AFV
• 1pool gt2cms X 2cm

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Tips for best assessment process

• Do CTG first
• Assess fetal state, do when fetus awake
• Transverse fetal abdomen image with limbs
• Score out of 10 - without CTG it is incomplete
• USS part 0,2,4,6 or 8/8
• 6 or 8/8 normal
• BUT for amniotic fluid ALWAYS an abnormal result

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DOPPLER IN OBSTETRICS

• Flow velocity waveform-spectral display
• Influenced by
• cardiac function
• vessel wall characteristics
• viscosity
• downstream vascular arrangement

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DOPPLER IN PREGNANCYKEY POINTS

• Need to understand basic principles
• Is user dependent
• Established roles fetal welfare assessment
• assessment of anaemia
• fetal echocardiography
• Potential roles screening for preeclampsia
• uses for venous doppler
• Fetal circulation has low resistance throughout
• absent or reversed velocities abnormal

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UMBILICAL ARTERIAL DOPPLER

• Mid portion of cord
• In fetal quiescence
• Use RI or PI
• Progressive fall in resistive indices throughout
  normal pregnancy
• Angle, sample volume important
• Extremes of fetal heart rate will affect result

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

• 30 reduction in perinatal death
• 40 reduction in admissions
• ? deliverieslt 34 weeks
• No differences in C/S or fetal distress in labour

Cochrane review2000
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Fetal growth restriction
Fetal overgrowth
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Normal Spiral Arteriole Thin walled
Abnormal Spiral Arteriole
Thick walled
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Umbilical Doppler
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FETAL VENOUS DOPPLER

• Venous Doppler
• a marker of fetal cardiac dysfunction
• influenced by fetal behavioural state esp FBM
• Umbilical vein non pulsatile
• pulsatile decreased forward flow at end diastole
• Ductus Venosus M shaped waveform
• reversed velocities abnormal
• proposed uses TTTS
• aneuploidy screening 1st T
• anaemia

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FETAL DOPPLER SUMMARY

• Umbilical artery well assessed
• Trend through gestation important
• Absent end diastolic velocities or reversed
  velocites always abnormal
• Doppler does not tell when delivery should occur
• Later in gestation fetus less tolerant of
  abnormal Doppler
• Pulsatile umbilical vein may be preterminal

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Uterine artery assessment
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UTERINE ARTERY FLOW VELOCITY WAVEFORMS Upper
panel normal waveform Lower
panel abnormal with notching
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Uterine arterial dopplera problem of a low
prevalence condition

• Poor predictor of preterm birth
• Ultrasound Obstet Gynecol. 2004
  Sep24(4)Second-trimester uterine artery
  Doppler and spontaneous preterm
  delivery.Cobian-Sanchez F, Prefumo F, Bhide A,
  Thilaganathan B.
• Poor predictor of PET, FGR P.N.Mortality.
• BJOG. 2000 Feb107(2)196-208How useful is
  uterine artery Doppler flow velocimetry in the
  prediction of pre-eclampsia, intrauterine growth
  retardation and perinatal death? An
  overview.Chien PF, Arnott N, Gordon A, Owen P,
  Khan KS.

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USS tests of fetal wellbeing

• Amniotic fluid assessment
• Biophysical profile
• Umbilical artery doppler
• Umbilical vein doppler
• (Uterine artery doppler)
• (Mean cerebral artery (MCA) doppler)