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Doppler and IUGR
Danny Wu, MBChBClinical InstructorDivision of Maternal Fetal MedicineObstetrics, Gynecology and Reproductive SciencesUCSF
Outline
• Background of Doppler ultrasound• IUGR• Fetal cardiovascular changes by Doppler
– Arterial• Umbilical artery• Middle Cerebral Artery
– Venous• Ductus Venosus
Physics of Doppler Ultrasound
Doppler frequency shift
v = fd.c / 2 ft.cos θ
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Doppler Ultrasound Safety in Pregnancy
• Diagnostic ultrasound is safe• Doppler ultrasound diagnostic equipment
has greater time-averaged intensities.• In vitro and animal experiments
– potential bio-effects by thermal, cavitational, or other mechanisms.
• ALARA principle (As Low As Reasonably Achievable)
In-utero Growth Restriction
• ACOG defined IUGR as EFW < 10th percentile• 4 million birth per year -- 400,0000 babies are
IUGR• Consequences
– At birth and in infancy– Childhood and adult life : Barker Hypothesis
• Risk of hypertension, hypercholesterolemia, coronary heart disease, impaired glucose tolerance and diabetes
• Enormous burden
Not All IUGR Are the Same
• Small for gestational age (SGA)– “constitutionally small”
• Pathologically small – Maternal illness present– Fetal pathology present
– No obvious reason
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Optimal Timing of Delivery
• Despite over 10000 publications on the topic, confusion remains– Definition– IUGR is not a homogenous group – Mode of testing
• Timing of delivery for early IUGR is highly controversial
Fetal Circulation
Dopplers
placenta
ArterialUmbilical Artery
MCA
VenousUmbilical Vein
Ductus Venosus
Uterine artery
Umbilical Artery Doppler
Doppler waveform represents downstream impedance to flow
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Doppler Waveform Analysis Normal Variations
• Gestational age– As GA advances, S/D declines
• Fetal heart rate– Negative correlation– If FHR 120-160, not significant variation
• Fetal breathing– Should perform sampling during fetal apnoea
• Site of sampling– Free loop preferred
GA
Umbilical artery Doppler
• As placental insufficiency worsens, diastolic flow progressively decreases
Morrow RJ; Adamson SL; Bull SB; Ritchie JW SOAm J Obstet Gynecol 1989 Oct;161(4):1055-60.
Decreased Absent Reversed
30% 70%Abnormal Vasculature
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Absent End Diastolic Flow Reversed End Diastolic Flow
Perinatal Outcomes
• Absent or reversed flow is associated with adverse perinatal outcome
• It may be present for weeks before additional sign of fetal compromise occurs
Doppler in High Risk Pregnancy
• Eleven RCTs involving nearly 7000 women were included
• Reduction in perinatal deaths (OR 0.71)• Fewer inductions of labor (OR 0.83)• Fewer admissions to hospital • No difference fetal distress in labor• No difference caesarean delivery
Cochrane Database Syst Rev. 2000;(2):CD000073
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Routine Doppler in Low Risk Pregnancy
• Not Recommended• Five trials were included which recruited
14,338 women
• No benefit
Cochrane Database Syst Rev. 2008
PhysiologicalChanges
Increased placental vascular resistance
Shunting to vital organs“Brain-sparing”
Impaired cardiacfunctions
UA S/D increases
MCA P/I decreases
Abnormal venous flow
Doppler Changes
MCA Doppler
Brain Sparing Effect
Cerebral Circulation“Brain Sparing Effect”
Cerebral Blood Flow
• Hypoxemia
• Hypoxemia + Acidemia
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MCA Doppler1. Fetus at rest2. Circle of Willis3. Zoom – MCA 50% of
screen4. Sample volume 1mm
placed between origin of carotid and the middle of the artery
5. Angle between USS and blood flow = 0°
6. Consistent waveforms7. Repeat 3 times
Doppler Waveform Analysis
Example of an MCA Doppler tracing at 27 weeksMiddle Cerebral Artery
IUGR
MCA PI PO2
MCA PI PO2 2 – 4 SD
MCA PI PO2 < 4 SD
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Mari et al Ultrasound Obstet Gynecol 2007; 29:310-316
Mari et al Ultrasound Obstet Gynecol 2007; 29:310-316
MCA - PI or - PSV?
• MCA - PSV predicts perinatal mortality more accurately than MCA - PI
• Reason:– MCA - PI tends to normalize before delivery
or demise– MCA - PSV tends to slightly decrease just
before delivery or demise BUT it remains elevated
Venous Dopplers
Reflects fetal cardiac functionPredictive of adverse perinatal outcome
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Ductus Venosus Qualitative Assessmnet
• Blood flow should always be antegrade
• Absent or reversed flow is alwaysabnormal
SD
A
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Semi-quantitative Assessment Outcomes related to Doppler changes
Baschat et al Ultrasound Obstet Gynecol 2006; 27: 41–47
Venous Doppler abnormalityis the strongest predictor
Doppler Abnormality Perinatal Mortality
SD elevated 5.6%
AEDF/REDF 11.5%
Venous 38.8%
Baschat.Ultrasound Obstet Gynecol 2004; 23: 111–118
Arterial and venous Dopplers among IUGR fetuses
Baschat et al Ultrasound Obstet Gynecol 2006; 27: 41–47
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Timing of Delivery
• Abnormal venous Doppler selects out the fetuses that are at highest risk
• Limited options:1) Wait2) Deliver
• Gestational age remains a major factor for adverse perinatal outcome especially in very preterm infants
Baschat et al Obstet Gynecol vol 109 , no.2(1), 2007
Intact Survival Neonatal Mortality
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Other considerations
• Picconi et al 2008– 19 fetuses with IUGR followed prospectively– 14 fetuses demonstrated intermittent DVRF
with median time to delivery or death in 13 days (1-57 days)
– Among those with continuous : median interval of 7 days (1-23 days)
– Cord pH and BE available for 10 fetuse: • Only one had abnormal pH and another one with
BE
Sequence of Doppler Changes is Dependent on the Underlying Cause
Key Points
• IUGR is not a homogenous group• Doppler study to characterize fetal
cardiovascular changes offer promise when managing early IUGR
• Currently there is no good data on– What is the best test
– When is the best time
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Thank You