Key words
dopplersonography - fetal surveillance - guideline - clinical application
Indications
The technical principles and quality criteria for performing Doppler sonography in
pregnancy have been recently defined [1].
Primary indications for the use of Doppler sonography are listed in the Maternity
Guidelines ([Table 1]). In addition, there are now further indications that are contained in the present
recommendations ([Table 2]).
Table 1
Indications for the use of Doppler sonography according to the Maternity Guidelines.
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suspicion of fetal growth restriction (FGR), pregnancy-induced hypertension, preeclampsia
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status post FGR or IUFT
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status post preeclampsia/eclampsia
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abnormalities of the fetal heart rate (CTG)
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suspicion of malformation/fetal disorder
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multiple pregnancy with discordant growth
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suspicion of heart defects or fetal arrhythmias
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Table 2
Additional indications for the use of Doppler sonography according to the DEGUM (German
Society for Ultrasound in Medicine) recommendations.
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pre-existing maternal vascular diseases (hypertension, nephropathy, D. mellitus, auto-immune
diseases)
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diagnosis and monitoring of fetal growth restriction (FGR)
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suspicion of fetal anemia
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suspicion of fetal infection
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fetal hydrops
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monitoring of monochorionic multiple pregnancies (FFTS (TOPS, TAPS), TRAP, sFGR)
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diagnosis of pathological umbilical cord insertions and vasa previa
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diagnosis of placental disorders (e. g. placenta increta)
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Screening
Numerous studies in the 2nd and 3 rd trimesters have demonstrated that increased uterine
artery indices ([Fig. 1a, b]) are associated with more frequent occurrence of preeclampsia, fetal growth restriction
(FGR), premature placental abruption, stillbirth, etc. [2]
[3]
[4]. Measurement of the uterine arteries in “low-risk” cohorts between 18+ 0 and 24+ 0 gestational weeks resulted in sensitivities of 40–60 % with a false-positive rate
around 10 %. However, the positive predictive values of 25 % for predicting FGR and/or
preeclampsia were very low [5]. Nevertheless, the method is suitable for exclusion diagnostics due to the negative
predictive value of 97–99 %. If the Doppler of the uterine artery is unremarkable,
the risk of developing severe preeclampsia is very low, and further management of
the pregnancy can be modified accordingly [6].
Fig. 1 Spectral Doppler of the right a and left b uterine arteries at 21 + 5 gestational weeks with low end-diastolic flow and notching
(arrow). The mean pulsatility index from both uterine arteries is > 1.40 and lies
above the 90th percentile.
In “high-risk” cohorts, the results were better (sensitivity 70–80 %, PPV 50 %) [7]. However, no effect on perinatological outcome could be demonstrated [8].
At the time of first trimester screening (11+ 0–14+ 0 gestational weeks), the accuracy of predicting preeclampsia by Doppler ultrasonography
of the uterine arteries alone is low; detection is 30–40 % with an FPR of 10 %. When
using a multimodal algorithm (Fetal Medicine Foundation, London) that incorporates
other anamnestic, biophysical (e. g., maternal BMI and blood pressure), and biochemical
(e. g., PIGF, PAPP-A) parameters, the accuracy of predicting early preeclampsia (< 34+ 0 gestational weeks) improves tremendously; detection rate 90–95 %, FPR 10 % [9]
[10]
[11]
[12]. This form of PE screening in first trimester screening is clinically relevant because
prophylactic administration of ASA before 16+ 0 gestational weeks can significantly reduce the occurrence and severity of early preeclampsia
[13]. Depending on the aspirin dose, the incidence of severe PE can be reduced to one-quarter,
and the total number of PE can be reduced to one-half on average [14]
[15]. The recommended dose is 150 mg ASA per day in the evening [15].
The technique of measuring the uterine arteries in the 1st trimester ([Fig. 2a, b]) differs compared with the 2nd and 3 rd trimesters and should meet certain quality criteria [16]. In particular, the measurement must be taken close to the cervix in the main branch
of the uterine artery. Pulsatility at this time is significantly higher than in the
2nd trimester, and in the majority of pregnancies notching is still detectable, so this
alone is not pathologically significant [17].
Fig. 2 Spectral Doppler of the right a and left b uterine arteries at 12 + 4 weeks measured from abdominal and lateral to the cervix,
with very low end-diastolic flow (arrow) and a mean pulsatility index from both uterine
arteries > 2.40, above the 90th percentile.
Transferring the multimodal screening concept to the 2nd and 3rd trimesters also achieves a high detection rate of 85 % with a false-positive rate
of 10 % for early preeclampsia [18]. However, it should be noted that this means that the preventive effect of ASA treatment
is significantly lower and that the screening benefit is the adaptation of the monitoring
intervals and the time of delivery.
The umbilical artery ([Fig. 3]) is not suitable for screening for FGR, preeclampsia, or other pathologies [19].
Fig. 3 Spectral Doppler of the umbilical artery at 25 + 1 weeks in pregnancy with FGR, with
low end-diastolic flow (arrow) and a pulsatility index (PI) above the 90th percentile.
Monitoring of high-risk pregnancies
Monitoring of high-risk pregnancies
The importance of the use of Doppler sonography in obstetrics must ultimately be measured
by the prevention of complications and the reduction of perinatal or neonatal morbidity
and mortality.
In principle, a distinction must be made between pregnancies with pathological Doppler
values without vs. with clinical fetal (FGR) and/or maternal symptoms (preeclampsia).
Pathological uterine Doppler findings ([Fig. 1], [2]) are almost always measurable long before the development of clinical symptoms (early
warning effect), while pathological fetal Doppler findings ([Fig. 3]) are practically always detectable shortly before or with the onset of complications
(e. g., FGR).
If it is already assumed that measurement of the uterine arteries is becoming increasingly
important, especially in the context of first trimester screening for risk assessment
of various complications, the question arises whether monitoring of pathological findings
are useful in the further course of pregnancy. There is clear evidence that the adaptation
of uterine perfusion to the needs of pregnancy continues well beyond the 1st half
of pregnancy [17]
[20]. That is, pathological findings in first trimester screening ([Fig. 2]) may normalize and formerly normal findings in this screening may become pathological.
Since this has prognostic significance for the individual pregnancy [17], we recommend monitoring uterine perfusion between 20+ 0 and 24+ 0 weeks.
In case of persistence of pathological uterine Doppler findings according to a “Uterine
Artery Score” (UAS; PI of both uterine arteries > 1.4 or 1.2 or notch) [21], a check-up between 26+ 0 and 28+ 0 weeks (biometry, Doppler, placenta) is recommended to detect early-onset deterioration
of fetal hemodynamics in a timely manner [21]
[22]. The perinatal risk profile increases significantly if more than 2 of the above
parameters (Uterine Artery Score = UAS) are pathological in the sum of both sides
[23]. At a UAS of 4, weekly clinical and Doppler sonographic checks are recommended.
In this case, supplemental serum screening by sFlt-1/PlGF ratio is also discussed,
but generally accepted management protocols are still pending [24].
Employment of fetal Doppler sonography usually begins with the onset of complications
to assess fetal status. This can be as early as the first trimester (e. g., ductus
venosus in FFTS in multiples), but usually becomes necessary after 20+ 0 weeks (FGR, PE, anomaly, anemia).
The most important vessel is the umbilical artery (UA), for which there is clear evidence
regarding its benefit for perinatal outcome [25]. It is the first vessel in the temporal cascade to assess fetal status [26], which is complemented by measurement of the middle cerebral artery (MCA) and ductus
venosus (DV) when the umbilical artery becomes pathological ([Fig. 3]).
In recent years, it has become clear that early severe FGR differs from late FGR in
the cascade of Doppler sonographic changes [26]
[27]
[28]. In the early form, as the pathology increases, Doppler indices in the umbilical
artery ([Fig. 3], [4], [5]), later in the middle cerebral artery ([Fig. 6]), and just before fetal decompensation, those of the venous duct ([Fig. 7]) become conspicuous. According to the TRUFFLE study, the decision criterion for
delivery before 34+ 0 weeks is considered to be negative or reversal of the a-wave in the ductus venosus
([Fig. 7]) in addition to the STV in the cCTG (short-time variability in computer-supported
CTG) [29]. After the appearance of pathological Doppler indices in the umbilical artery ([Fig. 3]), individualized monitoring begins, which should now be performed by a specialist
at shorter intervals after 1–2 weeks. Many different fetal parameters (biometry, amniotic
fluid volume, middle cerebral artery, DV, cCTG, biophysical profile, gestational weeks)
as well as maternal conditions (history, symptoms) play a modifying role, but in particular
the development of the individual Doppler parameters over time (no, slow or rapid
deterioration) [26], which also determine the need for inpatient monitoring and the administration of
antenatal steroids for lung maturation prophylaxis [30]. Using a cerebro-placental ratio (CPR) could further improve the prediction of the
outcome of perinatal disorders [31].
Fig. 4 Spectral Doppler of the umbilical artery with absent end-diastolic flow (AEDF) (arrow)
at 29 + 5 weeks of pregnancy with FGR.
Fig. 5 Spectral Doppler of the umbilical artery with reversed flow (arrows) at 23 + 2 weeks
in pregnancy with severe, early FGR.
Fig. 6 Spectral Doppler of the right middle cerebral artery at 26 + 3 weeks with high diastolic
flow (brain-sparing) (arrow) in pregnancy with FGR and pathological umbilical perfusion.
Fig. 7 Spectral Doppler of the ductus venosus with negative a-wave (reversed-flow) (arrows)
at 32 + 0 weeks in pregnancy with severe FGR, AEDF in the UA, brain-sparing in the
MCA, immediately before elective Cesarean section.
With the more common late fetal growth discrepancy in the third trimester, a distinction
must be made between SGA (small for gestational-age) and true FGR (fetal growth restriction).
This is only possible with multimodal approaches in which Doppler findings play an
important role [31]
[32].
In this late period, the end of adaptive mechanisms is reached with fetal circulatory
centralization in the middle cerebral artery, which is best documented by the cerebro-placental
ratio (CPR) [31]
[33]
[34]. Prediction of perinatal outcome disorders by CPR is good for individual parameters
in FGR [31], perhaps successful multimodally in SGA fetuses [31]
[35], and inadequate in unselected pregnancies [36]
[37]. This could perhaps also be related to methodological problems and a lack of quality
criteria for measuring CPR to date [38]. The umbilical artery and venous duct may also show elevated indices, but are usually
not highly pathological (e. g., zero flow, reverse flow) [30]
[34].
Doppler sonography in fetal anemia
Doppler sonography in fetal anemia
Direct and definitive diagnosis of fetal anemia is made by cordocentesis, an invasive
procedure that results in fetal loss due to the procedure in 1 % of cases, depending
on gestational age. Doppler sonographic detection of elevated peak systolic velocity
(PSV) in the middle cerebral artery is currently the best method to non-invasively
diagnose fetal anemia and to serially monitor the fetus if the risk is appropriate
([Fig. 8]) [39]. In anemia, there is an increase in blood flow rates in all fetal vessels – arteries
and veins – as a result of increased cardiac output and decrease in blood viscosity.
Primarily for technical reasons, peak systolic velocities (PSV) in the MCA are best
suited to detect the presence and extent of anemia, regardless of its etiology. The
decrease in hemoglobin and pCO2 correlate with MCA-PSV, but not the pO2
[40]; fetal anemia is not a hypoxemia-triggered blood redistribution, because pO2, pCO2 and pH are normal, as are the Doppler indices (PI, RI) or the Doppler spectrum in
the arterial and venous vessels.
Fig. 8 Spectral Doppler of the middle cerebral artery at 21 + 0 weeks with very high maximum
systolic velocity (arrow) in pregnancy with proven PV-B19 infection and fetal anemia.
At this point, it should be mentioned with respect to differential diagnosis that
even with severe and early onset of fetal growth restriction, not only is the pulsatility
in the middle cerebral artery reduced, but PSV can also be raised [41]. In late pregnancy, fetal hypercapnia may occur in the setting of progressive placental
insufficiency with prolongation of the villous diffusion distance, which may also
lead to flow acceleration in the middle cerebral artery [40]. In this case, the diagnostic value is therefore limited.
Other less sensitive signs of fetal anemia may include: cardiomegaly with biventricular
dilatation, hepatomegaly, splenomegaly, increased echogenicity of the bowel, polyhydramnios,
placentomegaly, and hydrops fetalis [42]
[43].
Fetal anemia is present when hemoglobin concentration and/or hematocrit are below
two standard deviations of the gestational age-related reference range. Since both
increase with increasing gestational age (mean fetal hemoglobin concentration is 10.6 g/dL
at 18+ 0 gestational weeks, 12.0 g/dL at 24+ 0 weeks, 12.8 g/dL at 30+ 0 weeks, and 13.8 g/dL at 40+ 0 weeks) [39], hemoglobin concentration is calculated as the multiple of median (MoM) relative
to gestational age, so that the extent of anemia can be specified independently of
gestational age (mild anemia: MoM 0.83–0.65; moderate anemia: MoM: 0.64–0.55; severe
anemia: MoM < 0.55) [39].
Since MCA-PSV increases during pregnancy from 20–30 cm/s at the end of the first trimester
to 50–70 cm/s in the third trimester, the PSV (cm/s) is also converted to MoM to express
the extent of deviation of PSV from the mean value independent of gestational age
[39].
To realize the diagnostic potential of Doppler sonography of MCA-PSV, the measurement
must be performed extremely carefully and accurately by an experienced examiner as
described in detail in the section on the method [1].
Immunologically induced fetal anemia
Immunologically induced fetal anemia
In a prospective study of 111 pregnancies with Rh incompatibility, the sensitivity
with respect to moderate and severe fetal anemia was 100 % and the false-positive
rate was 12 % when the MCA-PSV exceeded the cutoff of 1.5 MoM [39], thus reducing invasive procedures by about 70 % (serial amniocentesis) that would
otherwise be required. The choice of intervals between measurements depends on the
respective measured velocities in the case of blood group incompatibility [39]. After 35+ 0 gestational weeks, the proportion of false-positive results increases. Other studies
showed slightly worse results [44]
[45].
In case of blood group incompatibility confirmed by detection of maternal alloimmune
antibodies (critical titer usually ≧ 1:16, in case of Kell incompatibility ≧ 1:8),
paternal zygosity is determined first; if necessary, direct genotyping of the fetus
from amniotic fluid or from free fetal DNA in maternal blood [46] or from amniotic fluid is subsequently performed. If the fetus has the appropriate
antigen, fetal monitoring by serial measurements of MCA-PSV starts at 16+ 0–20+ 0 weeks and is then performed every 1–2 weeks, or at shorter intervals in the case
of borderline findings and/or other indications [47]
[48].
To determine the timing of repeat intrauterine blood transfusion, velocity measurement
in the middle cerebral artery is also suitable, but with limitations. Due to the smaller
size and viscosity of the previously transfused adult erythrocytes, the MCA-PSV is
higher for the same hemoglobin concentration than for fetuses that have not yet been
transfused; the optimal borderline after a transfusion was 1.69 MoM, not 1.5 MoM [49]. Because of the mixture of fetal and adult erythrocytes, velocity measurements in
the MCA alone are not adequate to fully estimate the extent of anemia, and a daily
hemoglobin drop of 0.3 g/dL should be assumed for timing further transfusions [49]
[50]
[51].
The key advantages of measuring PSV are noninvasive serial monitoring and avoidance
of amniocentesis or cordocentesis. Furthermore, early detection of fetal anemia with
subsequent therapy prevents the occurrence of fetal hydrops. The number of transfusions
required cannot be reduced [51]
[52].
Non-immunologically-induced fetal anemia
Non-immunologically-induced fetal anemia
Measurement of MCA-PSV is also applicable in fetal anemias of other causes ([Table 3]), and in almost all hemolytic and nonhemolytic anemias, such as parvovirus B19,
Kasabach-Merritt sequence, fetomaternal transfusion, and TAPS. An exception regarding
the strict inverse correlation between MCA-PSV and fetal Hb is fetal α-thalassemia
[53]
[54]. In this case, the method of choice is the measurement of the cardiothoracic ratio
(CTR). Even in the first trimester, a CTR > 0.5 is the best diagnostic parameter (sensitivity
97 % with a false-positive rate of 9 %) [54].
Table 3
Causes of fetal anemia.
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aplastic anemia
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hemolytic anemia
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bleeding anemia
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In the case of sonographic evidence of non-immunological fetal hydrops, measurement
of MCA-PSV allows simple, rapid, and reliable detection or exclusion of anemia, in
the presence of which intrauterine blood transfusion can immediately improve the condition
of these usually severely anemic fetuses.
Parvovirus B19 infection
The first and early 2nd trimesters appear to be the critical period of fetal parvovirus B19 infection. Transplacental
transmission of the virus to the fetus results in consecutive apoptosis of erythroid
progenitor cells and transient aplastic anemia. Placentitis, hepatitis, and myocarditis
may develop with generalized infection [55]
[56]. Myocarditis appears to be responsible for more frequent signs of cardiac dysfunction
in contrast to fetuses with blood group incompatibility.
Severe anemia is developed almost exclusively in fetuses almost exclusively during
the first and second trimesters; this can lead to fetal hydrops in about 5–10 % and
death of the fetus in about 3–5 % around 2–6 weeks after infection; severe fetal anemia
occurs less frequently in infections after 16+ 0 weeks of gestation [55]
[56].
If maternal PV B19 infection is detected, regular Doppler sonographic measurements
of MCA-PSV up to 12 weeks after the time of maternal infection are recommended [56]
[57].
Highly-elevated PSV is found in PV B19-induced fetal anemia in the first and early
second trimesters ([Fig. 8]). This may be associated with thickened nuchal translucency, cardiomegaly, skin
edema (“space suit” phenomenon), polyhydramnios, placentomegaly, and hyperreflective
bowel [43]. Since intrauterine transfusions before 20+ 0 gestational weeks are difficult and have a higher rate of complications, it seems
reasonable to perform intrauterine transfusion not as soon as MCA-PSV is elevated,
but only when there are discrete signs of hydrops [42]
[43].
Feto-maternal transfusion
Feto-maternal transfusion
The majority of feto-maternal transfusions with subsequent fetal anemia occur in the
third trimester, rarely result in hydrops, but may end up as IUFT. Decreased fetal
movements and pathologic fetal heart rate tracings on CTG are an indication of this.
Causes may include placental disorders, in combination with fetal growth restriction
and preeclampsia, as well as maternal abdominal trauma or external turning. Anemia
due to feto-maternal transfusion should be rapidly detected or excluded by Doppler
ultrasonography of the middle cerebral artery in all of these constellations [58]
[59].
Other fetal anemias
Other uncommon fetal anemias also result in increased flow velocities in the middle
cerebral artery ([Table 3]). Extremely rare aplastic and hemolytic anemias requiring transfusion in the fetal
period occur in Blackfan-Diamond syndrome, erythrocyte membrane defects, glucose 6-phosphate
dehydrogenase deficiency, type VII mucopolysaccharidosis, or congenital dyserythropoietic
anemia (CDA I and II). Not quite as rare are anemias in the context of Kasabach-Merritt
sequence in chorangiomas, hepatic hemangiomas, or diffuse hemangiomatosis, as well
as in coccygeal teratomas. Fetal cytomegaly infection or syphilis are not infrequently
associated with anemia and thrombocytopenia of the fetus, although the anemia is rather
mild or moderate, even if fetal hydrops is present. Limited to fetuses with trisomy
21, transient myelopoiesis (transient myeloproliferative disorder, TMD) may be responsible
for fetal anemia [60]. Finally, in a few cases of in utero anemia requiring transfusion, the cause is not found antenatally or postnatally [58].
For an accurate diagnosis of rare fetal anemia, it is critical that extensive blood
tests be performed at the time of the first fetal blood draw to narrow down the cause
of the anemia. This is hardly possible in already transfused fetuses; the same applies
to the detection of fetal HbF cells in maternal blood in case of feto-maternal transfusion
[58].
Doppler sonography for twin pregnancies
Doppler sonography for twin pregnancies
Doppler sonography of the fetal vessels is a key monitoring modality in the care of
multiple pregnancies. Staging and management are largely determined by Doppler findings.
Determination of chorionicity in the first trimester is essential for counseling and
differentiated further care [61]. Doppler sonography of the uterine arteries is of secondary importance in multiples
[62].
In dichorionic pregnancies, Doppler sonography is essentially used analogously to
singleton pregnancies. Here, the more frequent incidence of complications to be monitored,
such as FGR and PE, should be noted, also the use in the case of anomalies.
The exceptions arise in complications of monochorionic multiple pregnancies. Classic
twin transfusion syndrome (feto-fetal transfusion syndrome, FFTS) is caused by vascular
anastomoses between the placental portions of the multiples [63]. Sonographically, the donor twin has oligohydramnios up to a “stuck twin” and a
slightly filled to empty bladder, while the recipient twin has polyhydramnios and
a full urinary bladder. Further staging includes Doppler criteria that reflect the
hemodynamic changes in the fetus [64]. The donor typically shows an increase in pulsatility in the umbilical artery, while
the recipient has a cardiac load due to the increase in volume in the form of an increase
in pulsatility in the ductus venosus up to a negative or reverse a-wave and pulsations
in the umbilical vein. The gold standard of treatment for FFTS is laser coagulation
of the anastomoses at the placental surface [65]. Even after such procedures, regular sonographic or Doppler sonographic checks of
the umbilical artery, ductus venosus and middle cerebral artery are required to monitor
fetal growth or cardiac function.
Twin-anemia-polycythemia sequence (TAPS) is another complication of monochorionic
multiple pregnancies. In this case, major Hb differences occur between the two fetuses
via minute (< 1 mm) arterio-venous anastomoses, with anemia of the donor and polycythemia
of the recipient [66]. It is notable that further symptoms of classical FFTS are almost never detectable.
TAPS appears to occur spontaneously in 3–5 % of monochorionic twins, mostly in the
second half of pregnancy, however in 12–16 % of twins with TOPS (twin-oligohydramnion-polyhydramnion-sequence)
after laser coagulation, but reduced by the Solomon technique with dichorionization
of the placentas [67]
[68]. The diagnosis of TAPS can be easily made by the Doppler sonographic measurement
of the MCA-PSV; PSV > 1.5 MoM for anemia of the donor (sensitivity 94 %, specificity
74 %); PSV < 1.0 MoM for the polycythemia of the recipient (sensitivity 97 %, specificity
96 %) [69]; a delta MCA-PSV > 0.5 MoM [70] or > 0.373 [71] between the two fetuses can be an indication of TAPS even with normal PSV and correlates
with the hemoglobin difference.
A rare TRAP sequence (twin-reversed-arterial-perfusion) is diagnosed in addition to
the morphological changes of a multiple (acardius, acranius) by Doppler sonography
on the basis of the typical flow reversal in the umbilical artery. In this case, flow
reversal occurs early in pregnancy via an arterio-arterial anastomosis and ultimately
leads to cardiac arrest in the transfused twin [72]. The cardiac stress of the pumping twin should be monitored by Doppler sonography
in the venous compartment.
According to the German guideline for monitoring and care of twins [73], selective fetal growth restriction (sFGR) is present regardless of chorionicity
if a multiple shows an estimated weight < 3 rd percentile.
For dichorionic twins at least 2 of the 3 following parameters must be met for sFGR:
estimated weight of one multiple < 10th percentile, weight difference of both multiples
> 25 % or umbilical artery PI of the smaller multiple > 95th percentile.
For monochorionic multiples, at least 2 of 4 parameters must be met: estimated weight
of one multiple < 10th percentile, weight difference of both multiples > 25 % or umbilical
artery PI of the smaller multiple > 95th percentile [73]. In contrast to dichorionic multiples, in monochorionic pregnancies, sFGR is classified
into three types, with Doppler findings being crucial [74].
Type 1 with consistently positive end-diastolic flow in the umbilical artery has the most
favorable prognosis. Type 2 with end-diastolic zero flow or negative flow (AREDF) throughout the umbilical artery
is associated with a high risk of morbidity and mortality, as expected. Most challenging
is the monitoring and management of Type 3 with intermittent cyclic AREDF in the umbilical artery, alternating with normal flow
patterns due to arterio-arterial anastomoses. Here, the flow rate in the umbilical
Doppler sonogram must be set to slow to record sufficient cycles to monitor the flow
pattern over an extended period of time. Type 3 is at high risk of sudden IUFT or
neurological damage.
Anemia of the surviving twin
Anemia of the surviving twin
After death of a monochorionic twin, spontaneously or after selective fetocide, related
anemia of the surviving fetus not infrequently occurs in a few hours to days. This
effect is caused by a more or less rapid and large blood loss into the placental vascular
bed, rarely also into the other twin [75]. This complication can be detected by close-meshed assessment of MCA-PSV and cardiac
contractility and filling, initially every hour immediately after the procedure, so
that an intrauterine blood transfusion can be given on an emergency basis.
Summary
Doppler sonography of the maternal, uterine and fetal vessels is a method that is
now widely used in prenatal and obstetric medicine. The great advantage lies in the
fact that the method is non-invasive and can be used repeatedly if employed correctly.
Doppler sonography of the uterine and fetal vessels alone is not a suitable single
procedure for screening. However, incorporated into multimodal algorithms, Doppler
findings of uterine arteries are an important pillar of prediction accuracy. In particular,
screening for early PE in the first trimester has high accuracy. This is all the more
significant because ASA provides an effective prophylaxis for PE.
The Doppler findings of the fetal arteries play a major role in the diagnosis of the
condition and monitoring of high-risk pregnancies. The changes in the Doppler findings
in the UA, MCA and venous duct in their chronological order are important for monitoring
the early FGR. The venous duct can be used to optimize the birth management of the
fetuses with FGR. The cerebro-placental ratio (CPR) appears to be the most suitable
for predicting and monitoring late FGR; a final assessment is still pending, however.
The measurement of the maximum systolic velocity in the middle cerebral artery is
of significant importance for the diagnosis of fetal anemia. Thus, former invasive
diagnostics with a high complication rate could be replaced by a non-invasive method.
Both the indication and the monitoring of fetuses requiring transfusions are very
successful.
The advantages of using Doppler sonography seem obvious. This has been proven in a
large number of studies for various aspects of the child's outcome after a complicated
progression. Ultimately, however, the critical question remains whether perinatal,
neonatal, or early childhood morbidity or mortality can be improved. So far, this
has only been confirmed for the use of the umbilical artery in high-risk pregnancies.
The clinical utility of Doppler sonographic findings depends crucially on the quality
of the examination. It is therefore essential that the specified quality criteria
are applied in every examination. Accurate methodological application coupled with
correct physiological or pathophysiological interpretation ensure the success of the
use of Doppler sonography. Parts 1 and 2 of this “Best Practice Guideline for Doppler
Sonography” are intended to provide the foundation for this.
