Fetal Doppler: Umbilical Artery, Middle Cerebral Artery, and Venous System Giancarlo Mari, MD,* and Farhan Hanif, MD † One of the most important applications of Doppler ultrasonography in obstetrics is the detection of fetal anemia in pregnancies complicated by either red-cell alloimmunization or by other causes of fetal anemia. Doppler of the umbilical artery also has prognostic value in pregnancies affected by twin–twin transfusion syndrome undergoing in-utero interven- tion. Another potential major application is the use of Doppler ultrasound in the manage- ment of intrauterine-growth-restricted fetuses. At the present time, there is no single test that appears superior to the other available tests for timing the delivery of the growth- restricted fetus. Therefore, the decision to deliver a fetus, especially at <32 weeks, remains mostly based on empirical management. Doppler may provide a more reliable and systematic basis for timing these deliveries. This review emphasizes the three following concepts: (a) normal and abnormal Doppler of the umbilical artery, middle cerebral artery, mitral and tricuspid valves, umbilical vein, and ductus venosus; (b) some clinical applications of Doppler sonography in obstetrics; and (c) potential future research of Doppler in obstetrics. Semin Perinatol 32:253-257 © 2008 Elsevier Inc. All rights reserved. KEYWORDS feat anemia, IUGR, Doppler, ductus venosus, middle cerebral artery Umbilical Artery U mbilical artery angle independent indices (pulsatility index or systolic/diastolic (S/D) ratio) decrease with ad- vancing gestation because of a decreased placental vascular resistance, which physiologically occurs with advancing ges- tation. 1,2 In pathologic conditions, such as in intrauterine- growth-restricted (IUGR) fetuses, the umbilical artery wave- forms change and the angle-independent indices become abnormal (values above their reference ranges). These changes reflect an increased placental vascular resistance. 2 Giles and coworkers demonstrated that the number of pla- cental arteries per high power field is decreased in cases of abnormal umbilical artery Doppler. 3 Only in pregnancies with suspected intrauterine growth restriction and/or hyper- tensive disease of pregnancy does the use of umbilical artery Doppler reduce the number of perinatal deaths and unnec- essary obstetric interventions. 4 Middle Cerebral Artery Angle-independent indices differ among the different cere- bral arteries. 5 The middle cerebral artery is the most studied cerebral artery because (a) it is easy to sample; (b) it provides information on the cerebral blood flow in normal and IUGR fetuses; and (c) it can be sampled at an angle of 0° between the ultrasound beam and the direction of the blood flow. 6 Therefore, for the middle cerebral artery we are able to de- termine angle-independent indices (the most used is the pul- satility index) and also the real velocity of blood flow. In IUGR fetuses there is a redistribution of the blood flow from the fetal periphery to the brain. This phenomenon is called the “brain-sparing effect.” 7 Umbilical Vein After 15 weeks gestation, the umbilical vein normally has a continuous blood flow but becomes pulsatile in pathological cases, such as in IUGR and hydropic fetuses. 8 For the umbil- ical vein we use a qualitative assessment: continuous versus pulsatile blood flow. Atrioventricular Valves The atrioventricular valves (mitral and tricuspid) are charac- terized by two peaks—the “E” wave that corresponds to the *Tennessee Maternal Fetal Medicine Institute, Memphis, TN. †Department of Obstetrics and Gynecology, Wayne State University, De- troit, MI. Address reprint requests to Giancarlo Mari, MD, Director of Tennessee Ma- ternal Fetal Medicine Institute, Director MFM and Vice Chairman Ob/ Gyn, UTHSC, 853 Jefferson Avenue Rout E-102, Memphis, TN 38103- 2807. E-mail: gmari@utmem.edu 253 0146-0005/08/$-see front matter © 2008 Elsevier Inc. All rights reserved. doi:10.1053/j.semperi.2008.04.007