Role of Doppler Sonography in Obstetrics (2025)


Fetal Arterial Doppler


Umbilical Artery


The umbilical arterial circulation is normally a low-impedance circulation, with an increase in the amount of end-diastolic flow with advancing gestation. Umbilical arterial Doppler waveforms reflect the status of the placental circulation, and the increase in end-diastolic flow that is seen with advancing gestation is a direct result of an increase in the number of tertiary stem villi that takes place with placental maturation ( Fig. 22-3 ). Diseases that obliterate small muscular arteries in placental tertiary stem villi result in a progressive decrease in end-diastolic flow in the umbilical arterial Doppler waveforms until absent, and then reverse flow during diastole is noted ( Fig. 22-4 ). Reversed diastolic flow in the umbilical arterial circulation represents an advanced stage of placental compromise and is associated with more than 70% of placental arterial obliteration. The notation of absent or reversed end-diastolic flow in the umbilical artery is commonly associated with severe FGR and oligohydramnios. Only in pregnancies with suspected FGR does the use of umbilical artery Doppler sonography reduce the number of perinatal deaths and unnecessary obstetric interventions.




Role of Doppler Sonography in Obstetrics (1)



Doppler waveforms of the umbilical artery in a normal fetus in the third trimester of pregnancy. Note the increased end-diastolic velocity (D), consistent with a low impedance circulation. S, peak systole.




Role of Doppler Sonography in Obstetrics (2)



Abnormal umbilical artery Doppler waveforms; decreased end-diastolic velocity ( A ), absent end-diastolic velocity ( B ), reversed end-diastolic velocity ( C ).



Doppler waveforms of the umbilical arteries can be obtained from any segment along the umbilical cord. Waveforms obtained from the placental end of the cord show more end-diastolic flow and thus lower ratio values (resistive index [RI], systole/diastole [S/D] ratio) than waveforms obtained from the abdominal cord insertion. There are differences in Doppler indices of arterial waveforms obtained from different anatomic locations of the same umbilical cord, but they are generally minor and have no significance in clinical practice ( Tables 22-1 through 22-3 ). In 2013, the International Society for Ultrasound in Obstetrics and Gynecology (ISUOG) recommended taking Doppler measurements from a free loop of cord for the sake of simplicity and consistency.



TABLE 22-1


Reference Values for Serial Measurements of the Umbilical Artery Systolic-Diastolic Ratio















































































































































































































































































Gestation (weeks) SYSTOLIC-DIASTOLIC RATIO, BY PERCENTILE
2.5th 5th 10th 25th 50th 75th 90th 95th 97.5th
19 2.73 2.93 3.19 3.67 4.28 5.00 5.75 6.26 6.73
20 2.63 2.83 3.07 3.53 4.11 4.80 5.51 5.99 4.43
21 2.51 2.70 2.93 3.36 3.91 4.55 5.22 5.67 6.09
22 2.43 2.60 2.83 3.24 3.77 4.38 5.03 5.45 5.85
23 2.34 2.51 2.72 3.11 3.62 4.21 4.82 5.22 5.61
24 2.25 2.41 2.62 2.99 3.48 4.04 4.63 5.02 5.38
25 2.17 2.33 2.52 2.88 3.35 3.89 4.45 4.83 5.18
26 2.09 2.24 2.43 2.78 3.23 3.75 4.30 4.66 5.00
27 2.02 2.17 2.35 2.69 3.12 3.63 4.15 4.50 4.83
28 1.95 2.09 2.27 2.60 3.02 3.51 4.02 4.36 4.67
29 1.89 2.03 2.20 2.52 2.92 3.40 3.89 4.22 4.53
30 1.83 1.96 2.13 2.44 2.83 3.30 3.78 4.10 4.40
31 1.77 1.90 2.06 2.36 2.75 3.20 3.67 3.98 4.27
32 1.71 1.84 2.00 2.29 2.67 3.11 3.57 3.87 4.16
33 1.66 1.79 1.94 2.23 2.60 3.03 3.48 3.77 4.06
34 1.61 1.73 1.88 2.16 2.53 2.95 3.39 3.68 3.96
35 1.57 1.68 1.83 2.11 2.46 2.87 3.30 3.59 3.86
36 1.52 1.64 1.78 2.05 2.40 2.80 3.23 3.51 3.78
37 1.48 1.59 1.73 2.00 2.34 2.74 3.15 3.43 3.69
38 1.44 1.55 1.69 1.95 2.28 2.67 3.08 3.36 3.62
39 1.40 1.51 1.64 1.90 2.23 2.61 3.02 3.29 3.54
40 1.36 1.47 1.60 1.85 2.18 2.56 1.96 3.22 3.48
41 1.33 1.43 1.56 1.81 2.13 2.50 2.90 3.16 3.41

From Acharya G, Wilsgaard T, Bernsten GKR, et al: Reference ranges for serial measurements of umbilical artery Doppler indices in the second half of pregnancy. Am J Obstet Gynecol 192:937, 2005.



TABLE 22-2


Resistance Index of the Umbilical Artery Between 20 and 40 Weeks of Gestation





















































































































Gestation (weeks) Resistance Index, by Percentile
5th 50th 95th
20 0.567 0.690 0.802
21 0.557 0.680 0.793
22 0.548 0.671 0.784
23 0.539 0.663 0.776
24 0.530 0.655 0.768
25 0.522 0.646 0.760
26 0.514 0.639 0.752
27 0.506 0.631 0.745
28 0.498 0.623 0.737
29 0.490 0.615 0.730
30 0.482 0.608 0.723
31 0.474 0.600 0.715
32 0.465 0.592 0.707
33 0.457 0.584 0.700
34 0.449 0.576 0.692
35 0.440 0.567 0.684
36 0.431 0.559 0.675
37 0.422 0.550 0.667
38 0.412 0.540 0.657
39 0.402 0.530 0.648
40 0.390 0.519 0.637

From Merz E (ed): Ultrasonography in Obstetrics and Gynecology, vol 1. Stuttgart, Thieme, 2005, pp 469-480, 614.



TABLE 22-3


Pulsatility Index of the Umbilical Artery Between 20 and 40 Weeks of Gestation





















































































































Gestation (weeks) PULSATILITY INDEX, BY PERCENTILE
5th 50th 95th
20 0.940 1.216 1.505
21 0.913 1.189 1.476
22 0.890 1.165 1.450
23 0.869 1.142 1.427
24 0.849 1.122 1.405
25 0.831 1.102 1.385
26 0.813 1.084 1.365
27 0.798 1.065 1.346
28 0.780 1.048 1.327
29 0.764 1.031 1.308
30 0.748 1.014 1.290
31 0.732 0.997 1.272
32 0.716 0.980 1.254
33 0.700 0.963 1.236
34 0.684 0.946 1.218
35 0.668 0.928 1.199
36 0.651 0.910 1.180
37 0.634 0.891 1.160
38 0.615 0.872 1.139
39 0.595 0.851 1.117
40 0.573 0.828 1.093

From Merz E (ed): Ultrasonography in Obstetrics and Gynecology, vol 1. Stuttgart, Thieme, 2005, pp 469-480, 614.



Middle Cerebral Artery


The MCA is the most accessible cerebral vessel to ultrasound imaging in the fetus, and it carries more than 80% of cerebral blood flow. The cerebral circulation is normally a high-impedance circulation with continuous forward flow throughout the cardiac cycle. In the presence of fetal hypoxemia, central redistribution of blood flow occurs, resulting in increased blood flow to the brain ( Fig. 22-5 ), heart, and adrenals and a reduction in flow to the peripheral and placental circulations. This blood flow redistribution is known as the brain-sparing effect and plays a major role in fetal adaptation to oxygen deprivation.




Role of Doppler Sonography in Obstetrics (3)



Doppler waveforms of the middle cerebral artery in a normal fetus ( A ) and in a hypoxemic fetus ( B ). Note the increase in end-diastolic velocity in fetus B resulting from a low-impedance cerebral circulation as part of the brain-sparing reflex.



The right and left middle cerebral arteries represent major branches of the circle of Willis in the fetal brain. The circle of Willis, which is supplied by the internal carotid and vertebral arteries, can be imaged with color flow Doppler sonography in a magnified axial plane of the fetal head obtained at the base of the skull, at the level of the thalami and wings of sphenoid bone ( Fig. 22-6 ). In this plane, the proximal and distal middle cerebral arteries are seen in their long axis, with their course almost parallel to the ultrasound beam. As such, the insonating beam, which is parallel to the vessel and thus has an angle of insonation of 0 degrees, will result in a measured velocity that accurately reflects the true velocity of blood in this vessel (cos 0 = 1). MCA Doppler waveforms, obtained from the proximal third portion of the vessel, immediately after its origin from the circle of Willis, have shown the best reproducibility ( Tables 22-4 and 22-5 and Fig. 22-7 ).




Role of Doppler Sonography in Obstetrics (4)



Circle of Willis shown on color Doppler imaging. ACA, anterior cerebral artery; MCA, middle cerebral artery; PCA, posterior cerebral artery.


(From Ultrasound in Obstetrics & Gynecology: A Practical Approach. Available at www.openultrasound.com . Used with permission.)



TABLE 22-4


Reference Values for the Resistance Index of the Middle Cerebral Artery






































































































































Gestation (weeks) RESISTANCE INDEX, BY PERCENTILE Gestation (weeks) RESISTANCE INDEX, BY PERCENTILE
5th 50th 95th 5th 50th 95th
18 0.544 0.687 0.787 31 0.652 0.798 0.907
19 0.574 0.708 0.808 32 0.645 0.792 0.902
20 0.592 0.727 0.828 33 0.636 0.783 0.894
21 0.608 0.744 0.846 34 0.625 0.773 0.885
22 0.622 0.758 0.861 35 0.612 0.761 0.873
23 0.633 0.771 0.874 36 0.597 0.747 0.86
24 0.643 0.782 0.886 37 0.579 0.73 0.844
25 0.651 0.79 0.895 38 0.56 0.712 0.826
26 0.656 0.796 0.902 39 0.539 0.692 0.807
27 0.659 0.801 0.907 40 0.515 0.669 0.785
28 0.661 0.803 0.91 41 0.489 0.644 0.761
29 0.66 0.803 0.911 42 0.462 0.618 0.735
30 0.657 0.801 0.91

From Bahlmann F, Reinhard I, Krummenauer F, et al: Blood flow velocity waveforms of the fetal middle cerebral artery in a normal population: reference values from 18 weeks to 42 weeks of gestation. J Perinat Med 30:490, 2002.



TABLE 22-5


Reference Values for Umbilical Artery (UA) and Middle Cerebral Artery (MCA) Resistance Indices, as Well as Their Ratio, by Percentile





































































































































































































































Gestation (weeks) UA RESISTANCE INDEX MCA RESISTANCE INDEX RATIO
5th 50th 95th 5th 50th 95th 5th 50th 95th
24 0.615 0.717 0.828 0.778 0.867 0.696 0.809 0.968
25 0.605 0.707 0.819 0.789 0.881 0.676 0.791 0.955
26 0.594 0.697 0.810 0.795 0.892 0.658 0.775 0.945
27 0.583 0.687 0.802 0.798 0.898 0.642 0.761 0.937
28 0.572 0.678 0.793 0.797 0.901 0.628 0.750 0.932
29 0.562 0.668 0.785 0.793 0.900 0.616 0.740 0.929
30 0.551 0.658 0.776 0.786 0.897 0.606 0.732 0.928
31 0.540 0.648 0.767 0.776 0.891 0.597 0.726 0.929
32 0.530 0.638 0.759 0.764 0.883 0.590 0.722 0.931
33 0.519 0.629 0.750 0.750 0.872 0.585 0.719 0.936
34 0.508 0.619 0.742 0.734 0.860 0.581 0.717 0.941
35 0.498 0.609 0.733 0.717 0.846 0.578 0.717 0.949
36 0.487 0.599 0.724 0.698 0.831 0.576 0.718 0.957
37 0.476 0.589 0.716 0.677 0.814 0.575 0.720 0.967
38 0.465 0.580 0.707 0.655 0.795 0.576 0.724 0.978
39 0.455 0.570 0.699 0.632 0.776 0.577 0.728 0.991
40 0.444 0.560 0.690 0.607 0.755 0.580 0.734 1.004
41 0.433 0.550 0.681 0.582 0.734 0.583 0.740 1.018
42 0.423 0.540 0.673 0.556 0.711 0.588 0.747 1.034

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