What is the role of MCA Doppler studies in the treatment of hemolytic disease of the newborn (HDN)?

Updated: Dec 28, 2017
  • Author: Sameer Wagle, MBBS, MD; Chief Editor: Muhammad Aslam, MD  more...
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Answer

The peak systolic middle cerebral artery (MCA) Doppler velocity has proved to be a reliable screening tool to detect fetal anemia and has replaced amniocentesis. The MCA is easily visualized with color-flow Doppler; pulsed Doppler is then used to measure the peak systolic velocity just distal to its bifurcation from the internal carotid artery. Because the MCA velocity increases with advancing gestational age, the result is reported in multiples of median (MOMs). In recent studies, the sensitivity for detection of moderate and severe fetal anemia has been proven to be 100%, with a false-positive rate of 10% at 1.5 MOM. [59] It has been shown to reduce the need for invasive diagnostic procedures such as amniocentesis and cordocentesis by more than 70%. [59]

MCA Doppler studies can be started as early as 18 weeks' gestation but are not reliable after 35 weeks' gestation. [60]  It has also been used to time the subsequent fetal transfusion and to diagnose anemia from multiple causes, such as in twin-twin transfusion. The MCA slope from 3-weekly readings is now used to predict fetal risk for severe anemia (see the image below). [61]

Slopes for peak systolic velocity in middle cerebr Slopes for peak systolic velocity in middle cerebral artery (MCA) for normal fetuses (dotted line), mildly anemic fetuses (thin line), and severely anemia fetuses (thick line).

With acquisition of experience in performing MCA Doppler study, serial amniocentesis for detecting fetal anemia has been used to lesser extent. [62]


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