Maternal Hemodynamics in Preeclampsia and FGR: Ultrasound Parameters

Why Evaluate Maternal Hemodynamics

The ISUOG 2025 consensus considers ultrasound assessment of maternal hemodynamics as a clinical tool in hypertensive disorders of pregnancy and fetal growth restriction/FGR. The same blood pressure value can correspond to different mechanisms: high cardiac output, high vascular resistance, reduced preload, left ventricular remodeling, or diastolic dysfunction. Therefore, the ultrasound report should answer not only the question "is there hypertension," but also "what hemodynamic profile underlies the clinical picture."

The practical goal of the study is to standardize measurements, identify the phenotype, track dynamics, and help the multidisciplinary team interpret maternal and fetal risk. The consensus does not replace the diagnosis of preeclampsia, does not establish the timing of delivery, and does not offer a universal numerical cut-off for all devices and gestational ages.

Who Should Be Evaluated

The most justified scenarios: chronic hypertension in pregnancy, gestational hypertension, preeclampsia, suspicion of early or late FGR, combination of hypertension and fetal growth restriction, clinical deterioration, signs of volume overload or heart failure, and the need to understand the response to therapy. The study is especially useful when the obstetric picture is ambiguous: blood pressure is moderately elevated, but there is severe placental insufficiency; or conversely, significant hypertension is accompanied by normal fetal growth.

Minimum Data Set

ISUOG emphasizes that hemodynamics should be assessed simultaneously: blood pressure, heart rate, and ultrasound parameters are collected in one visit, in a standardized position, and with the gestational age indicated. Isolated CO without pressure or SVR without the calculation method is uninformative.

How to Calculate Key Indicators

The basic echocardiographic pathway is to measure the diameter of the left ventricular outflow tract, obtain the LVOT area, record the pulsed-wave Doppler VTI in the LVOT, and calculate the stroke volume. Then CO is obtained by multiplying SV by HR, and CI by dividing CO by body surface area. Vascular resistance is calculated from MAP and CO; the protocol must specify the formula used and assumptions made.

The consensus emphasizes reproducibility: the same patient position, synchronous pressure measurement, correct alignment of the Doppler beam, averaging stable cardiac cycles, and avoiding interpretation of a single poor-quality spectrum. For dynamic monitoring, it is more important to use the same method and comparable conditions than to mechanically compare values obtained by different technologies.

Echocardiography: What Matters Beyond CO

In preeclampsia and FGR, cardiac output does not describe the whole picture. It is necessary to assess LV geometry, signs of concentric remodeling, left atrial size, systolic function, and diastolic filling. LVEF may remain preserved with clinically significant diastolic dysfunction or increased afterload, so a comprehensive conclusion is preferable to a single indicator.

GLS can detect subclinical impairment of longitudinal function but should be interpreted considering image quality, software, and local references. Diastolic parameters also depend on HR, preload, and gestational age; they cannot be automatically transferred from the non-pregnant population without context.

Hemodynamic Phenotypes

It is practically useful to conclude the report with a phenotype. It is not a separate diagnosis but helps understand the mechanism of hypertension and choose the direction of monitoring. ISUOG emphasizes integration: pressure, CO/CI, TPR/SVR, and echocardiographic signs should be interpreted together.

Connection with FGR

In FGR, the maternal profile may explain part of the placental hemodynamics. The low-volume vasoconstrictor variant potentially combines with high afterload and insufficient uteroplacental perfusion. However, the diagnosis of FGR is not made based on maternal CO or SVR: fetal biometry, growth rates, amniotic fluid, and fetal-placental circulation Doppler according to current obstetric protocols are mandatory.

The hemodynamic report is useful in dynamics: worsening vascular resistance, flow decline, or the appearance of cardiac dysfunction in the mother should be correlated with changes in uterine arteries, umbilical artery, middle cerebral artery, and ductus venosus if they are investigated as indicated.

How to Formulate the Conclusion

Optimal structure: study conditions; gestational age; BP, MAP, and HR; method of obtaining SV/CO; values of SV, CO, CI, TPR/SVR; main echocardiographic findings; hemodynamic phenotype; quality limitations. It is important to clearly state whether pregnancy-specific references were used and whether correct comparison with previous studies is possible.

Example formulation: "Maternal hemodynamics: vasoconstrictor phenotype with relatively reduced flow; signs of concentric LV remodeling without overt systolic dysfunction according to the study. Interpretation performed in the context of gestational age, current antihypertensive therapy, and obstetric Doppler."

Limitations and Errors

The main error is using fixed non-pregnant thresholds as a universal norm for pregnant women. The second is drawing conclusions from a single calculated index without pressure and HR. The third is comparing studies conducted by different methods without describing the methodology. The fourth is substituting maternal hemodynamics for obstetric fetal assessment: these blocks complement each other but do not replace.

The ISUOG 2025 consensus sets the framework: standardization, integration, and clinical interpretation. Numbers are important, but the decisive factor is the profile, its dynamics, and consistency with the obstetric picture.