Doppler Use in Obstetrics

Danny Wu, MBChB FACOGClinical 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

• Fetal Anemia– MCA Doppler

Physics of Doppler UltrasoundDoppler frequency shift

v = fd.c / 2 ft.cos θ

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 -- 400,000 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

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

Doppler Waveform Analysis

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

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

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

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

QuickTime™ and aTIFF (Uncompressed) decompressor

are needed to see this picture.

Example of an MCA Doppler tracing at 27 weeks

Middle Cerebral ArteryIUGR

MCA PI PO2

MCA PI PO2 2 – 4 SD

MCA PI PO2 < 4 SD

Venous Dopplers

Reflects fetal cardiac functionPredictive of adverse perinatal outcome

Ductus Venosus

Qualitative Assessmnet

• Blood flow should always be antegrade

• Absent or reversed flow is alwaysabnormal

SD

A

Semi-quantitative Assessment

Outcomes related to Doppler changes

Baschat et al Ultrasound Obstet Gynecol 2006; 27: 41–47

Venous Doppler abnormalityis the strongest predictor

38.8%Venous

11.5%AEDF/REDF

5.6%SD elevated

Perinatal MortalityDoppler Abnormality

Baschat.Ultrasound Obstet Gynecol 2004; 23: 111–118

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

Neonatal Mortality

Intact Survival

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 : medianinterval of 7 days (1-23 days)

– Cord pH and BE available for 10 fetuse:• Only one had abnormal pH and another one with

BE

Key Points

• Doppler study to characterize fetal cardiovascular changes offer promise when managing early IUGR

• Currently there is no consensus on– What is the best test– When is the best time

MCA Doppler

Peak velocity flow correlates well with fetal anemia

Fetal Anemia

• Causes– Red cell alloimmunization

• eg Anti-D, Anti-Kell, Anti-c – Parvovirus infection – Chronic fetomaternal hemorrhage – Inherited RBC disorders

• eg Alpha Thalassemia

MCA Doppler in Fetal Anemia

• During anemia, – the blood viscosity ↓ the blood velocity ↑

• The correction of the fetal anemia lowers the fetal blood velocity.

Advantage of MCA peak velocity

• Cerebral arteries respond quickly to hypoxemia1

• Easily visualized with 0° angle1

• Low intra-observer and inter-observer variability2

1. Mari G et al Obstet Gynecol 2002; 99:589–5932. Mari G et al Middle cerebral peak systolic velocity:technique and variability. J Ultrasound Med2005; 24:425–430.

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

MCA PSV and Gestational Age

Mari et al 2000

• 111 fetuses at risk of Rh isoimmunisation vs 265 controls

• MCA-PSV (above 1.5 MoMs) for the prediction of moderate or severe anemia

• Sensitivity was 100% (95% CI 86-100), with a false positive rate of 12%

N Engl J Med 2000; 342:9-14.

Results

MCA Doppler vs Amniocentesis

• Oepkes et al • Multi-centered prospective study• 164 women with Rh(D), Rh(c), Rh(E), and

Fy(a) alloimmunized pregnancies with indirect antiglobulin titers ≥1:64 and antigen positive fetuses

N Engl J Med. 2006 Jul 13;355(2):156-64

Results

81 (72.0-88.0)81 (70.7-88.4)ΔOD450

Queenan’s

77 (67.3-84.0)76* (64.8-84.0)ΔOD450

Liley’s

82 ( 73.3 – 88.9 )88 ( 78.4-93.5 )MCA

Specificity% (CI)

Sensitivity% (CI)

Special Considerations • >35 week

– Higher false positive rate1

• After first transfusion– Useful to time repeat transfusion2

• After 2 transfusions– Correlations remains but data more limited3

1.Zimmerman et al RCOG 2002 Br J Obstet Gynaecol 109, pp. 746–7522.Detti et al AJOG Nov 2001, Pages 1048-1051 3.Mari et al AJOG 2005 Sep;193(3 Pt 2):1117-20

MCA After 1 Transfusion

Correlation after 2 Transfusions

Special Considerations

• Also useful in anemia due to other causes– Congenital parvovirus B19 infection1

– Maternal fetal hemorrhage2

– Twin-to-Twin Transfusion Syndrome3

1 Cosmi et al AJOG 2002 Nov;187(5):1290-3.2 Eichbaum et al Fetal Diagn Ther. 2006;21(4):334-8 3.Senat et al Am J Obstet Gynecol 2003; 189:1320–1324.

ACOG Technical Bulletin

• “ In a center with trained personnel and when the fetus is at an appropriate gestational age, middle cerebral artery Doppler measurements seem to be an appropriate noninvasive means to monitor pregnancies complicated by red cell alloimmunization”

ACOG Technical Bulletin no 75. 2006 Aug;108(2):457-64

Thank You