Recommendations for Prenatal Doppler in Daily Obstetric Practice - A Review

Abstract


INTRODUCTION
Doppler fluximetry in obstetrics refers to the use of Doppler ultrasound technology to assess blood flow patterns and velocities in the maternal and fetal circulations during pregnancy.It provides valuable information about the vascular dynamics in the placenta, umbilical cord, and fetal organs, aiding in the evaluation of fetal well-being and the identification of potential complications 1 .
The Doppler Effect, named after the Austrian physicist Christian Doppler, is a phenomenon that describes the change in frequency of sound or light waves as they are reflected by a moving object 2 .In obstetrics, Doppler ultrasound uses this principle to measure the velocity of blood flow in specific vessels.
Doppler fluximetry involves placing the ultrasound probe over the target blood vessel, such as the umbilical artery, middle cerebral artery, or uterine artery 3 .The Doppler ultrasound emits high-frequency sound waves that bounce off the red blood cells within the vessel.The returning waves are then analyzed to determine the velocity and waveform characteristics of the blood flow.
The parameters commonly assessed in Doppler fluximetry include: • Systolic/Diastolic Ratios: The ratio of peak systolic velocity to end-diastolic velocity, providing information about the resistance to blood flow.• Pulsatility Index (PI): Calculated as the difference between peak systolic and end-diastolic velocities divided by the mean velocity, reflecting the resistance and compliance of the vessel.• Resistance Index (RI): Similar to PI, the difference between peak systolic and end-diastolic velocities divided by the peak systolic velocity, assessing vascular resistance.By evaluating these parameters, Doppler fluximetry can provide insights into the uteroplacental and fetal circulations.Abnormal findings, such as increased resistance or altered blood flow patterns, may indicate placental insufficiency, fetal growth restriction, fetal anemia, or other complications.These findings can guide clinical management and help in making decisions regarding the timing and mode of delivery or further interventions 4,5 : It's essencial to note that the interpretation of Doppler findings should always be done in conjunction with other clinical data, such as fetal growth assessment, maternal health, and fetal well-being.

MEASUREMENT TECHNIQUES TO DOPPLER FLOWMETRY IN OBSTETRICS
There are several measurement techniques used in Doppler flowmetry in obstetrics to assess blood flow velocities and patterns.These techniques involve placing the Doppler ultrasound probe on specific blood vessels and obtaining measurements using various parameters.Here are some commonly used measurement techniques in obstetric Doppler flowmetry 6,7  The choice of measurement technique depends on the specific blood vessel being evaluated, the clinical question, and the expertise of the operator.Different techniques may be used for assessing blood flow in vessels like the umbilical artery, middle cerebral artery, uterine artery, or ductus venosus.
The interpretation of Doppler flowmetry measurements should always be done in conjunction with other clinical information to obtain a comprehensive assessment of fetal well-being and placental function.

INTERPRETATION OF DOPPLER FLOWMETRY IN OBSTETRICS
Interpretation of Doppler flowmetry in obstetrics involves analyzing the parameters obtained from Doppler ultrasound measurements to assess blood flow velocities and patterns.The interpretation aims to evaluate the vascular dynamics in the maternal and fetal circulations, identify potential abnormalities, and provide information about fetal well-being and placental function.Are some interpretations of Doppler flowmetry in obstetrics [8][9][10]

PARAMETRES DURING INTERPRETATION OF DOPPLER FLOWMETRY IN OBSTETRICS
Interpretation of Doppler flowmetry in obstetrics involves analyzing the parameters obtained from Doppler ultrasound measurements to assess blood flow velocities and patterns.These values help evaluate the vascular dynamics and provide information about fetal well-being and placental function.These parametres are: • Pulsatility Index (PI): The pulsatility index is a numeric value calculated as the difference between the peak systolic velocity and the end-diastolic velocity, divided by the mean velocity.

INTERPRETATION OF DOPPLER FLOWMETRY IN OBSTETRICS, BASED ON GESTATION AGE, AND CORRESPONDING VALUES
Interpretation of Doppler flowmetry in obstetrics, based on gestational age, involves assessing the blood flow velocities and patterns in various vessels and comparing them to reference ranges specific to each gestational age [11][12][13][14][15]

GENERAL AND SPECIFIC INDICATIONS FOR DOPPLER FLOWMETRY IN OBSTETRICS
Doppler flowmetry in obstetrics provides valuable information about fetal well-being, placental function, and the uteroplacental circulation.Are described below some general and specific indications for Doppler flowmetry in obstetrics [16][17][18] : General Indications:

DISCUSSION AND CONCLUSIONS
The Doppler ultrasound is a technique that evaluates blood flow velocity and patterns, through these parameters: Umbilical Artery Doppler: Measures blood flow in the umbilical artery, providing information about fetal-placental circulation.
Middle Cerebral Artery (MCA) Doppler: Assesses blood flow in the fetal brain, which can be useful for monitoring fetal anemia or assessing cerebral circulatory redistribution.
Ductus Venosus Doppler: Evaluates blood flow in the ductus venosus, aiding in assessing cardiac function and potential chromosomal abnormalities.
Uterine Artery Doppler: Assesses blood flow to the uterus, helping to identify placental insufficiency or predict preeclampsia.Doppler waveforms are assessed by examining the velocity and resistance of blood flow.Various indices, such as the pulsatility index (PI), resistance index (RI), and systolic/diastolic (S/D) ratios, may be used for interpretation.Abnormal Doppler findings may suggest placental insufficiency, fetal hypoxia, or other complications, and further management or interventions may be required.
Specific recommendations for Doppler flowmetry in obstetrics can vary depending on individual patient factors, local protocols, and the expertise of the healthcare provider.It is recommended to perform regular Doppler assessments to monitor the uteroplacental and fetal circulations.Doppler flowmetry is particularly valuable in high-risk pregnancies.High-risk conditions may include gestational hypertension, preeclampsia, diabetes, maternal cardiovascular disease, multiple pregnancies (twins, triplets), suspected fetal anomalies, decreased fetal movements, a history of fetal growth restriction (FGR) or Small for Gestational Age (SGA).The timing and frequency of Doppler assessments may vary depending on the specific indication, gestational age, and clinical context.Doppler flowmetry should be interpreted in conjunction with other clinical findings, including fetal growth assessment, maternal health, and fetal well-being.Combining Doppler results with biophysical profile (BPP) scores, non-stress tests (NSTs), or additional imaging studies provides a more comprehensive evaluation.
We have come to the conclusion that regular Doppler assessments can help assess fetal well-being, detect placental insufficiency, and guide management decisions regarding timing of delivery or interventions.
It's important to note that recommendations need to be determined are general in nature, and specific recommendations, which may vary based on individual circumstances.The use of Doppler flowmetry and interpretation of results should be performed by qualified healthcare professionals, such as obstetricians, perinatologists, or sonographers, who are trained in obstetric Doppler ultrasound and can consider the unique needs of each patient.
It reflects the resistance and compliance of the vessel being assessed.Higher PI values indicate increased resistance to blood flow.• Resistance Index (RI): The resistance index is another numeric value calculated as the difference between the peak systolic velocity and the end-diastolic velocity, divided by the peak systolic velocity.It also provides information about vascular resistance.Higher RI values suggest increased resistance to blood flow.• Systolic/Diastolic (S/D) Ratio: The S/D ratio is calculated by dividing the peak systolic velocity by the end-diastolic velocity.It indicates the relationship between the systolic and diastolic components of the waveform.An elevated S/D ratio may indicate increased resistance or altered blood flow patterns.Mean Arterial Blood Velocity: This value represents the average velocity of blood flow within the vessel being assessed.It provides information about the overall blood flow characteristics in the region of interest.
The interpretation of Doppler flowmetry in obstetrics should always be done in conjunction with other clinical data, such as fetal growth assessment, maternal health, and fetal well-being.The combination of Doppler findings with other parameters, such as biophysical profile (BPP) scores, non-stress tests (NSTs), or additional imaging studies, helps provide a comprehensive evaluation and guide clinical management decisions.
: Umbilical Artery Doppler:• Normal: A normal umbilical artery Doppler waveform is characterized by a forward flow throughout the cardiac cycle, with a low-resistance pattern.The waveform shows smooth deceleration during diastole.