SMFM clinical guideline
Doppler assessment of the fetus with intrauterine growth restriction

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Objective

We sought to provide evidence-based guidelines for utilization of Doppler studies for fetuses with intrauterine growth restriction (IUGR).

Methods

Relevant documents were identified using PubMed (US National Library of Medicine, 1983 through 2011) publications, written in English, which describe the peripartum outcomes of IUGR according to Doppler assessment of umbilical arterial, middle cerebral artery, and ductus venosus. Additionally, the Cochrane Library, organizational guidelines, and studies identified through review of the above were utilized to identify relevant articles. Consistent with US Preventive Task Force suggestions, references were evaluated for quality based on the highest level of evidence, and recommendations were graded.

Results and Recommendations

Summary of randomized and quasirandomized studies indicates that, among high-risk pregnancies with suspected IUGR, the use of umbilical arterial Doppler assessment significantly decreases the likelihood of labor induction, cesarean delivery, and perinatal deaths (1.2% vs 1.7%; relative risk, 0.71; 95% confidence interval, 0.52–0.98). Antepartum surveillance with Doppler of the umbilical artery should be started when the fetus is viable and IUGR is suspected. Although Doppler studies of the ductus venous, middle cerebral artery, and other vessels have some prognostic value for IUGR fetuses, currently there is a lack of randomized trials showing benefit. Thus, Doppler studies of vessels other than the umbilical artery, as part of assessment of fetal well-being in pregnancies complicated by IUGR, should be reserved for research protocols.

Section snippets

Umbilical artery Doppler

Doppler velocimetry of the umbilical artery assesses the resistance to blood perfusion of the fetoplacental unit (Figure 1, A). As early as 14 weeks, low impedance in the umbilical artery permits continuous forward flow throughout the cardiac cycle.7 Maternal or placental conditions that obliterate small muscular arteries in the placental tertiary stem villi result in a progressive decrease in end-diastolic flow in the umbilical artery Doppler waveform until absent (Figure 1, B) and then

Middle cerebral artery Doppler

Under normal conditions, the cerebral circulation is a high impedance circulation with continuous forward flow present throughout the cardiac cycle14 (Figure 2, A). The middle cerebral arteries, which carry >80% of the cerebral circulation, represent major branches of the circle of Willis and are the most accessible cerebral vessels for ultrasound imaging in the fetus.15 The middle cerebral artery can be imaged with color Doppler ultrasound in a transverse plane of the fetal head obtained at

Ductus venosus Doppler

Doppler waveforms obtained from the central venous circulation in the fetus reflect the physiologic status of the right ventricle. Doppler waveforms are obtained from the ductus venosus in a transverse or sagittal view of the fetal abdomen at the level of the diaphragm.22 By superimposing color Doppler on the gray-scale image, the ductus venosus can be identified as it branches from the umbilical vein (Table). Variable high flow velocities, reflected as a mixture of colors on color Doppler

Uterine artery Doppler

Doppler velocimetry of the uterine arteries reveals a progressive decrease in impedance with advancing gestational age.25, 26 This decrease in impedance is thought to reflect a maternal adaptation to pregnancy resulting from trophoblastic invasion of the maternal spiral arterioles in the first half of gestation.27 The uterine artery can be demonstrated by color Doppler velocimetry as it originates from the anterior division of the hypogastric artery, and just before it enters the uterus at the

Question 1. Should Doppler ultrasound assessment be performed in low-risk and/or high-risk women as a screening test for IUGR? (Levels II and III)

Routine umbilical artery Doppler screening for the subsequent development of IUGR in a low-risk population has not been shown to be effective in predicting IUGR. A metaanalysis of 4 trials (n = 11,375), which included 2 studies of low-risk populations and 2 studies of unselected populations, found no significant difference in antenatal hospitalization, obstetric outcomes, or perinatal morbidities with systematic use of umbilical artery Doppler as compared with control groups.32 The metaanalysis

Question 2. What are the benefits and limitations of Doppler studies of each vessel when IUGR is suspected? (Levels I, II, and III)

Clinicians have the options of interrogating several vessels, with umbilical artery, middle cerebral artery, and ductus venosus being the ones most studied.

Umbilical artery Doppler evaluation of pregnancies with suspected IUGR has been shown to significantly reduce inductions of labor (relative risk [RR], 0.89; 95% CI, 0.80–0.99), cesarean deliveries (RR, 0.90; 95% CI, 0.84–0.97), and perinatal deaths (RR, 0.71; 95% CI, 0.52–0.98; 1.2% vs 1.7%; number needed to treat = 203; 95% CI, 103–4352)

Question 3. What is the usual progression of Doppler abnormalities in suspected IUGR? Is this progression consistent/reliable? (Levels II and III)

In the presence of hypoxemia, adaptive changes in the fetal circulation can be detected by Doppler ultrasound examination. These changes manifest themselves in a variable fashion in different fetuses, but some general patterns of progression can be recognized. Early adaptation includes preferential shunting and distribution of blood flow to the fetal brain, heart, and adrenal glands at the expense of the splanchnic and peripheral circulation. This adaptive mechanism, termed “brain sparing,” is

Question 4. What Doppler study regimen should be initiated for suspected IUGR? What other antepartum testing may be helpful in this setting? (Levels I, II, and III)

Umbilical artery Doppler evaluation of the fetus with suspected IUGR can help differentiate the hypoxic growth-restricted fetus from the nonhypoxic small fetus, and thereby reduce perinatal mortality, and unnecessary interventions.2, 8, 35, 49, 50, 51, 52 Umbilical artery Doppler studies to assess for the presence of increased placental impedance and fetal cardiovascular adaptation to hypoxemia should be initiated when IUGR is suspected and the fetus is considered potentially viable. Umbilical

Question 5. What interventions are available and should be considered based on abnormal fetal Doppler velocimetry studies? (Levels II and III)

Umbilical artery Doppler blood flow studies can be used clinically to guide interventions such as the frequency and type of other fetal testing, hospitalization, antenatal corticosteroid administration, and delivery (Figure 5). Sometimes these Doppler studies can also help defer intervention. For example, in cases with suspected IUGR and absent or reversed end-diastolic flow <25 weeks, aggressive obstetrical interventions may be deferred until a later gestational age given the poor prognosis

Levels II and III evidence, level C recommendation

  • 1

    Doppler of any vessel is not recommended as a screening tool for identifying pregnancies that will subsequently be complicated by IUGR.

Levels I evidence, level A recommendation

  • 2

    Antepartum surveillance of a viable fetus with suspected IUGR should include Doppler of the umbilical artery, as its use is associated with a significant decrease in perinatal mortality.

Levels II and III evidence, level C recommendation

  • 3

    Once IUGR is suspected, umbilical artery Doppler studies should be performed usually every 1-2 weeks to assess for deterioration; if normal, they can be extended to less

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