UTA Doppler study
Uterine Arteries doppler & normal value
Normal Value
Non-Pregnant Uterine Artery Doppler
Non-Pregnant Uterine Artery Doppler evaluates blood flow in the uterine arteries and provides information about uterine and endometrial vascular resistance. It is useful in the assessment of pelvic vascularity, abnormal uterine bleeding, infertility, endometrial receptivity, uterine pathology, and selected gynecological conditions. The uterine arteries arise from the anterior division of the internal iliac arteries and course medially within the broad ligament before reaching the uterus.
Uterine Artery → The uterine artery is usually identified at the level of the cervical region and followed laterally along the side of the uterus. Color Doppler is used to identify the vessel, followed by pulsed-wave Doppler for spectral waveform analysis.
Uterine Artery Waveform:
The normal non-pregnant uterine artery demonstrates a low-resistance arterial waveform, particularly during the proliferative and secretory phases when uterine and endometrial vascularity changes with the menstrual cycle.
A normal waveform generally demonstrates:
• Sharp systolic upstroke
• Continuous forward diastolic flow
• Relatively low downstream resistance
• Variable resistance according to the menstrual cycle and hormonal status
The Doppler waveform should therefore be interpreted together with the menstrual phase, uterine morphology, endometrial thickness, and clinical indication.
Important Doppler Parameters:
1. Pulsatility Index (PI)
2. Resistance Index (RI)
3. S/D Ratio
S/D ratio → S/D ratio (Systolic/Diastolic ratio) is the ratio of peak systolic velocity (S) to end-diastolic velocity (D) in the uterine artery waveform. It provides an estimate of downstream uterine vascular resistance and is influenced by the physiological state of the uterus, including the menstrual cycle, pregnancy status, and menopause.
Formula:
S/D ratio = Peak Systolic Velocity (S) ÷ End-Diastolic Velocity (D)
What it measures:
The uterine arteries supply blood to the uterus and endometrium. In the non-pregnant state, uterine vascular resistance is relatively higher than during normal pregnancy. Consequently, the end-diastolic velocity is relatively lower and the S/D ratio is comparatively higher.
During normal pregnancy, progressive trophoblastic invasion and remodeling of the spiral arteries produce a marked reduction in uteroplacental vascular resistance. This results in increased diastolic flow and a lower S/D ratio. Therefore, S/D values from a non-pregnant uterus should not be interpreted using pregnancy-specific reference ranges.
Non-Pregnant Uterine Artery:
• Uterine artery vascular resistance is relatively high.
• End-diastolic flow is present but comparatively reduced.
• A diastolic notch may normally be present, particularly before pregnancy and in higher-resistance states.
• S/D ratio is generally higher than that observed during normal pregnancy.
• Interpretation should consider the woman's age, menstrual status, menopausal status and clinical indication.
Measuring technique for S/D:
1. Identify the uterine artery near its crossing with the internal iliac artery/external iliac artery region according to the examination protocol.
2. Use color Doppler to identify the uterine artery and confirm its characteristic pulsatile arterial waveform.
3. Position the PW Doppler sample volume within the uterine artery, avoiding adjacent vessels.
4. Maintain an appropriate Doppler angle; for velocity measurements, keep the angle as close to 0° as practical.
5. Record the waveform during a period of minimal patient movement.
6. Obtain at least 3 consecutive uniform waveforms for analysis.
7. Identify the peak systolic velocity (S) and end-diastolic velocity (D).
8. Calculate the S/D ratio as S ÷ D.
9. Record the right and left uterine artery separately; do not assume that one side represents the other.
10. If the waveform contains a prominent diastolic notch, document its presence because waveform morphology can provide additional information beyond the S/D ratio.
Important Interpretation:
The S/D ratio is a ratio-based index and can become very high when diastolic flow is very low. When the end-diastolic component is absent, the S/D ratio becomes difficult or impossible to interpret reliably. When diastolic flow is reversed, S/D is not an appropriate index for describing the waveform. Current Doppler guidance generally favors PI over S/D or RI when assessing uterine artery waveform resistance because PI has a more linear relationship with vascular resistance. :contentReference[oaicite:1]{index=1}
Reference Values – Non-Pregnant Uterine Artery S/D Ratio
Clinical Note:
There is no single universally accepted S/D cutoff for all non-pregnant women. Uterine artery Doppler indices vary according to age, hormonal status, menstrual cycle and measurement technique. Therefore, S/D should be interpreted together with the RI, PI, waveform morphology and clinical indication rather than using an isolated numerical cutoff. Studies of uterine artery Doppler have demonstrated substantial physiological variation between individuals and between the placental and non-placental sides during pregnancy. :contentReference[oaicite:2]{index=2}
RI → RI (Resistance Index) is a Doppler-derived index used to estimate downstream arterial vascular resistance. In the uterine artery, RI reflects the relationship between peak systolic and end-diastolic blood-flow velocities and is influenced by uterine vascular tone, hormonal status and the physiological state of the uterus.
Formula:
RI = (Peak Systolic Velocity − End-Diastolic Velocity) ÷ Peak Systolic Velocity
What it measures:
The uterine artery supplies blood to the uterus and endometrium. In the non-pregnant state, uterine vascular resistance is relatively high compared with pregnancy. Consequently, the end-diastolic velocity is relatively reduced and the RI is generally higher.
During pregnancy, progressive remodeling of the uteroplacental circulation produces a marked reduction in vascular resistance. Diastolic flow therefore increases and the uterine artery RI decreases. Non-pregnant uterine artery RI should therefore not be interpreted using pregnancy-specific reference ranges.
Non-Pregnant Uterine Artery RI:
• Relatively high resistance waveform compared with pregnancy.
• End-diastolic flow is present but relatively reduced.
• An early diastolic notch may normally be present.
• RI may vary with the menstrual cycle and hormonal status.
• RI should be interpreted together with PI, S/D ratio and waveform morphology.
Measuring technique for RI:
1. Identify the uterine artery using gray-scale and color Doppler imaging.
2. Use color Doppler to confirm the characteristic pulsatile arterial waveform.
3. Place the PW Doppler sample volume within the uterine artery, avoiding adjacent vessels.
4. Maintain an appropriate Doppler insonation angle and obtain a clean spectral waveform.
5. Record the waveform during a period of minimal patient movement.
6. Obtain at least 3 consecutive uniform waveforms.
7. Identify the peak systolic velocity (S) and end-diastolic velocity (D).
8. Calculate RI as (S − D) ÷ S.
9. Measure the right and left uterine arteries separately and document both values.
10. Note the presence or absence of an early diastolic notch because waveform morphology provides additional information about uterine arterial resistance.
Physiological Variation:
Uterine artery RI is not completely constant in non-pregnant women. Studies have demonstrated variation during the menstrual cycle. One Doppler study reported uterine artery RI values of approximately 0.43 during the follicular phase, 0.50 around ovulation and 0.41 during the luteal phase, illustrating that cycle-related differences can occur depending on the population and measurement technique. :contentReference[oaicite:1]{index=1} Other studies have reported substantially higher RI values in non-pregnant women, demonstrating the importance of sampling site, technique, population and menstrual/hormonal status when comparing reference values. :contentReference[oaicite:2]{index=2}
Reference Values – Non-Pregnant Uterine Artery RI
Clinical Interpretation:
A higher RI generally indicates greater downstream arterial resistance and relatively reduced diastolic flow. A lower RI indicates lower downstream resistance and relatively greater diastolic flow.
However, there is no single universally accepted RI cutoff for all non-pregnant women. RI varies with menstrual phase, hormonal status, age, sampling location and Doppler technique. Therefore, an isolated RI value should not be used to diagnose uterine pathology.
A 2026 study of uterine artery Doppler reported a mean RI of approximately 0.77 in the nongravid uterus, providing a useful contemporary population reference, but this should not be treated as a universal diagnostic cutoff. :contentReference[oaicite:3]{index=3} Reporting Recommendation:
Right uterine artery RI: ______
Left uterine artery RI: ______
Mean RI: ______
Diastolic notch: Present / Absent
PI → PI (Pulsatility Index) is a Doppler-derived index that describes the pulsatility of blood flow within the uterine artery. It reflects downstream vascular impedance and is particularly useful for assessing changes in uterine arterial resistance.
Formula:
PI = (Peak Systolic Velocity − End-Diastolic Velocity) ÷ Mean Velocity
What it measures:
The uterine arteries supply blood to the uterus and endometrium. In the non-pregnant state, uterine vascular resistance is generally higher than during normal pregnancy. Consequently, the uterine artery waveform usually demonstrates relatively reduced diastolic flow and a higher PI.
During pregnancy, progressive remodeling of the uteroplacental circulation produces a substantial reduction in vascular resistance. Diastolic flow increases and the uterine artery PI progressively decreases. Therefore, non-pregnant uterine artery PI should not be interpreted using gestational-age-specific pregnancy reference charts.
Non-Pregnant Uterine Artery PI:
• PI is generally higher than in normal pregnancy.
• Higher PI indicates greater downstream vascular impedance.
• Lower PI indicates relatively greater diastolic flow and lower vascular impedance.
• A protodiastolic notch may be present in the non-pregnant state.
• PI may vary according to age, hormonal status, menstrual phase and Doppler technique.
• Right and left uterine arteries should preferably be measured separately.
Measuring technique for PI:
1. Identify the uterine artery using gray-scale and color Doppler imaging.
2. Follow the uterine artery to an appropriate standardized measurement site according to the examination protocol.
3. Use color Doppler to confirm the arterial vessel and its pulsatile waveform.
4. Place the PW Doppler sample volume within the uterine artery, avoiding adjacent vessels.
5. Record several consecutive uniform cardiac cycles during minimal patient movement.
6. Identify the peak systolic velocity (S), end-diastolic velocity (D) and the mean velocity of the waveform.
7. Calculate PI as (S − D) ÷ Mean Velocity.
8. Obtain measurements from both the right and left uterine arteries.
9. If bilateral measurements are obtained, report the individual values and, where appropriate, the mean uterine artery PI.
10. Document the presence or absence of a diastolic notch because waveform morphology provides complementary information.
Reference Values – Non-Pregnant Uterine Artery PI:
Published nongravid reference values vary considerably between studies because of differences in population, ultrasound approach, sampling site and measurement methodology. A recent 2026 multicenter study involving nongravid women reported a mean uterine artery PI of approximately 2.07. :contentReference[oaicite:1]{index=1} An earlier study of 26 non-pregnant women reported a mean PI of 3.25 ± 0.83, with a calculated 95% reference range of approximately 1.21–5.29. :contentReference[oaicite:2]{index=2} Another study of non-pregnant women demonstrated mean PI values of approximately 2.30 in the follicular phase, 2.51 around ovulation and 2.50 in the mid-luteal phase, illustrating that physiological variation can occur across the menstrual cycle. :contentReference[oaicite:3]{index=3}
Suggested Reference Summary – Nongravid Uterine Artery PI
Clinical Interpretation:
A high PI indicates increased downstream uterine arterial impedance and relatively reduced diastolic blood flow. A low PI indicates lower impedance and relatively greater diastolic flow.
In the non-pregnant uterus, an elevated PI alone should not be considered diagnostic of uterine pathology because normal values show substantial inter-individual and methodological variation. PI should be interpreted together with RI, S/D ratio, waveform morphology, menstrual/hormonal status and the clinical indication.
The transition from the nongravid state to pregnancy is characterized by a substantial reduction in uterine artery PI as uteroplacental vascular resistance falls. A recent 2026 study demonstrated this progressive reduction in PI from the nongravid state through pregnancy. :contentReference[oaicite:4]{index=4} Reporting Recommendation:
Right uterine artery PI: ______
Left uterine artery PI: ______
Mean uterine artery PI: ______
Diastolic notch: Present / Absent
PSV → PSV (Peak Systolic Velocity) is the maximum blood-flow velocity recorded during systole in the uterine artery waveform. It represents the highest forward blood-flow velocity generated during ventricular contraction and can provide information about uterine arterial blood-flow dynamics.
Definition:
PSV = Maximum systolic blood-flow velocity measured during one cardiac cycle
What it measures:
The uterine arteries supply blood to the uterus and endometrium. In the non-pregnant state, uterine arterial blood flow is influenced by age, menstrual phase, hormonal status and vascular resistance. PSV therefore represents the peak velocity of arterial blood flow but should not be interpreted independently as a direct measure of vascular resistance.
Unlike PI, RI and S/D, PSV is an absolute velocity measurement and is strongly affected by the Doppler insonation angle, sample location, vessel diameter, cardiac output and technical settings.
Non-Pregnant Uterine Artery PSV:
• Represents the maximum systolic velocity in the uterine artery.
• PSV may vary considerably between individuals.
• Values may change with the menstrual cycle and hormonal status.
• PSV generally increases when uterine blood flow increases.
• PSV should be interpreted together with EDV, RI, PI and S/D ratio.
• Right and left uterine artery PSV should preferably be recorded separately.
Measuring technique for PSV:
1. Identify the uterine artery using gray-scale and color Doppler.
2. Follow the artery to a standardized measurement location according to the examination protocol.
3. Place the PW Doppler sample volume within the uterine artery.
4. Use an appropriate Doppler angle and apply angle correction for velocity measurement.
5. Keep the Doppler angle preferably ≤60° when technically possible.
6. Obtain several consecutive, uniform waveforms during minimal patient movement.
7. Identify the highest point of the systolic waveform as the Peak Systolic Velocity (PSV).
8. Record the velocity in cm/s.
9. Measure both right and left uterine arteries separately.
10. Avoid measuring during significant patient movement, vessel compression or an unstable waveform.
Important Technical Point:
Because PSV is an absolute velocity measurement, angle correction is essential. Unlike ratio-based indices such as RI and S/D, PSV cannot be reliably compared between examinations when substantially different Doppler angles are used.
Reference – Non-Pregnant Uterine Artery PSV
Clinical Interpretation:
A higher PSV indicates a greater peak systolic blood-flow velocity at the site of measurement, whereas a lower PSV indicates a lower peak systolic velocity. However, PSV alone does not directly quantify vascular resistance.
PSV should therefore be assessed together with RI, PI, S/D ratio and EDV. A change in PSV between examinations may also result from differences in Doppler angle, sample location, machine settings or cardiac output rather than a true change in uterine vascular physiology.
Reporting Recommendation:
Right uterine artery PSV: ______ cm/s
Left uterine artery PSV: ______ cm/s
Mean PSV: ______ cm/s
Doppler angle: ______°
EDV → EDV (End-Diastolic Velocity) is the blood-flow velocity measured at the end of diastole, immediately before the next systolic cardiac cycle. It represents the amount of forward blood flow that continues through the uterine artery during diastole and provides useful information about downstream vascular resistance.
Definition:
EDV = Blood-flow velocity measured at the end of diastole
What it measures:
The uterine artery supplies blood to the uterus and endometrium. In the non-pregnant state, uterine vascular resistance is generally higher than during normal pregnancy. Consequently, end-diastolic flow may be relatively reduced and the waveform may demonstrate a prominent diastolic notch.
When downstream vascular resistance decreases, more blood continues to flow during diastole and the EDV increases. When downstream resistance increases, diastolic flow decreases and the EDV falls.
EDV is therefore an important component of the RI, PI and S/D ratio calculations.
Relationship with Doppler indices:
• RI: RI = (PSV − EDV) ÷ PSV
• S/D: S/D = PSV ÷ EDV
• PI: PI = (PSV − EDV) ÷ Mean Velocity
A decrease in EDV generally causes RI and S/D to increase, while increased diastolic flow generally causes these indices to decrease.
Non-Pregnant Uterine Artery EDV:
• EDV is the end-diastolic component of the uterine artery waveform.
• It is usually lower than the PSV.
• EDV is influenced by uterine vascular resistance.
• EDV may vary with menstrual cycle, age and hormonal status.
• A prominent diastolic notch may be associated with relatively reduced diastolic flow.
• EDV should be interpreted together with PSV, RI, PI and S/D ratio.
• Right and left uterine artery EDV should preferably be documented separately.
Measuring technique for EDV:
1. Identify the uterine artery using gray-scale and color Doppler.
2. Place the PW Doppler sample volume within the uterine artery at the standardized examination site.
3. Obtain a clean spectral Doppler waveform with several consecutive uniform cardiac cycles.
4. Minimize patient movement and avoid vessel compression.
5. Identify the end-diastolic point immediately before the beginning of the next systolic upstroke.
6. Place the Doppler measurement cursor at the end-diastolic velocity point.
7. Record EDV in cm/s.
8. Measure both right and left uterine arteries separately.
9. Use the same sampling location and technical settings when comparing serial examinations.
Important Technical Point:
Because EDV is an absolute velocity measurement, the Doppler insonation angle affects the measured value. Appropriate angle correction should therefore be used for velocity measurements, preferably maintaining an angle of ≤60° when technically achievable.
Reference – Non-Pregnant Uterine Artery EDV
Clinical Interpretation:
A higher EDV indicates greater forward blood flow during diastole and generally corresponds to lower downstream vascular impedance. A lower EDV indicates reduced diastolic flow and generally corresponds to higher vascular impedance.
In the non-pregnant uterus, EDV should not be interpreted using pregnancy-specific reference ranges. There is considerable physiological variation, and EDV is strongly influenced by Doppler technique and insonation angle.
An isolated EDV value should therefore not be used to diagnose uterine pathology. It should be interpreted together with PSV, RI, PI, S/D ratio, waveform morphology and the clinical indication.
Reporting Recommendation:
Right uterine artery EDV: ______ cm/s
Left uterine artery EDV: ______ cm/s
Mean EDV: ______ cm/s
Diastolic notch: Present / Absent
Mean Velocity → Mean Velocity is the average blood-flow velocity calculated across the entire Doppler waveform during one cardiac cycle. In uterine artery Doppler, it represents the average velocity of blood flow throughout systole and diastole and is used in the calculation of the Pulsatility Index (PI).
Definition:
Mean Velocity = Average velocity of blood flow over the cardiac cycle
What it measures:
The uterine artery waveform contains periods of rapid systolic flow followed by lower-velocity diastolic flow. Mean velocity provides an estimate of the overall average blood-flow velocity during the measured cardiac cycle.
Unlike PSV and EDV, which represent specific points on the waveform, mean velocity incorporates the velocity throughout the cardiac cycle and is therefore particularly important for calculating the PI.
Relationship with PI:
PI = (Peak Systolic Velocity − End-Diastolic Velocity) ÷ Mean Velocity
Therefore, accurate determination of mean velocity is important when calculating the uterine artery PI.
Non-Pregnant Uterine Artery Mean Velocity:
• Represents the average blood-flow velocity throughout the cardiac cycle.
• Includes both systolic and diastolic blood-flow components.
• Is influenced by uterine vascular resistance and overall blood-flow conditions.
• May vary with age, menstrual phase, hormonal status and cardiac output.
• Is affected by the Doppler sampling site and technical parameters.
• Should not be interpreted as an isolated diagnostic parameter.
Measuring technique for Mean Velocity:
1. Identify the uterine artery using gray-scale and color Doppler.
2. Place the PW Doppler sample volume within the uterine artery at the standardized measurement site.
3. Obtain a stable spectral Doppler waveform containing several consecutive uniform cardiac cycles.
4. Minimize patient movement and avoid excessive pressure over the vessel.
5. Ensure an appropriate Doppler angle and use angle correction for absolute velocity measurements.
6. Record at least 3 similar consecutive waveforms.
7. Use the ultrasound system's automated waveform analysis, when available, to calculate the mean velocity over the cardiac cycle.
8. Confirm that the tracing is clean and that the automated contour accurately follows the waveform.
9. Measure the right and left uterine arteries separately.
10. Use the same technique and sampling location for serial examinations whenever possible.
Important Technical Point:
Mean velocity is an absolute velocity measurement. Therefore, measurement accuracy depends on Doppler angle, sample location, waveform quality and machine settings. For velocity measurements, an insonation angle of ≤60° is generally preferred when technically achievable.
Reference – Non-Pregnant Uterine Artery Mean Velocity
Clinical Interpretation:
Mean velocity should primarily be regarded as a supporting Doppler measurement rather than an independent marker of uterine vascular resistance. A high or low mean velocity does not by itself establish normality or abnormality.
For assessment of uterine arterial impedance, PI, RI and S/D ratio are more directly useful. Mean velocity is particularly important because it forms the denominator of the PI calculation.
In the non-pregnant uterus, no single universally accepted reference range for mean uterine artery velocity applies to all women. Values can vary substantially according to measurement technique, vessel location, menstrual phase and physiological state.
Reporting Recommendation:
Right uterine artery Mean Velocity: ______ cm/s
Left uterine artery Mean Velocity: ______ cm/s
Mean bilateral velocity: ______ cm/s
Measurement site: ______
Diastolic Notch → Diastolic Notch is a transient decrease in blood-flow velocity seen immediately after peak systolic flow and before the continuation of diastolic flow in the uterine artery waveform. It reflects relatively increased downstream vascular impedance and is an important qualitative feature of uterine artery Doppler assessment.
What it represents:
A diastolic notch appears as a brief downward deflection or interruption in the early diastolic portion of the uterine artery waveform. It is associated with relatively higher downstream vascular resistance and reduced early-diastolic blood flow.
In the non-pregnant uterus, a diastolic notch may be a normal finding because uterine vascular resistance is generally higher than during normal pregnancy. Therefore, the presence of a notch in a non-pregnant woman should not automatically be considered abnormal.
Types of Diastolic Notch:
• Early diastolic notch: Brief reduction in velocity immediately following systole.
• Unilateral notch: Notch present in only one uterine artery.
• Bilateral notch: Notch present in both right and left uterine arteries.
• Prominent notch: Clearly visible reduction in early-diastolic flow.
• Absent notch: Smooth transition from systolic flow into diastolic flow without a distinct early-diastolic interruption.
Non-Pregnant Uterine Artery:
• A diastolic notch may normally be present.
• Its presence generally indicates relatively higher uterine arterial resistance.
• Notch morphology may vary with age, menstrual cycle and hormonal status.
• Bilateral or prominent notching does not independently diagnose uterine pathology.
• The notch should be interpreted together with PI, RI, S/D ratio and clinical findings.
How to Assess the Diastolic Notch:
1. Identify the uterine artery using color Doppler.
2. Obtain a stable spectral Doppler waveform using PW Doppler.
3. Record at least 3 consecutive uniform cardiac cycles.
4. Examine the early-diastolic portion of the waveform immediately after the systolic peak.
5. Identify any distinct temporary decrease in velocity before the diastolic flow continues.
6. Record the finding as Present or Absent.
7. Document whether the notch is right-sided, left-sided or bilateral.
8. When appropriate, describe the notch as mild, moderate or prominent based on its visual appearance.
9. Correlate the waveform appearance with PI, RI and S/D ratio.
Diastolic Notch – Non-Pregnant Uterine Artery
Clinical Interpretation:
The diastolic notch is a qualitative waveform feature rather than a numerical Doppler index. In a non-pregnant woman, the presence of a notch can be physiological and should not be interpreted in isolation.
The clinical significance of a notch becomes more important when it is considered together with quantitative Doppler indices such as PI, RI and S/D ratio. A prominent notch accompanied by elevated resistance indices may indicate increased uterine arterial impedance, but the overall interpretation depends on the clinical context.
Reporting Recommendation:
Right uterine artery: Notch Present / Absent
Left uterine artery: Notch Present / Absent
Notch: Unilateral / Bilateral
Prominence: Mild / Moderate / Prominent
Right PI: ______
Left PI: ______
Uterine Artery → The uterine artery is usually identified at the level of the cervical region and followed laterally along the side of the uterus. Color Doppler is used to identify the vessel, followed by pulsed-wave Doppler for spectral waveform analysis.
Uterine Artery Waveform:
The normal non-pregnant uterine artery demonstrates a low-resistance arterial waveform, particularly during the proliferative and secretory phases when uterine and endometrial vascularity changes with the menstrual cycle.
A normal waveform generally demonstrates:
• Sharp systolic upstroke
• Continuous forward diastolic flow
• Relatively low downstream resistance
• Variable resistance according to the menstrual cycle and hormonal status
The Doppler waveform should therefore be interpreted together with the menstrual phase, uterine morphology, endometrial thickness, and clinical indication.
Important Doppler Parameters:
1. Pulsatility Index (PI)
2. Resistance Index (RI)
3. S/D Ratio
S/D ratio → S/D ratio (Systolic/Diastolic ratio) is the ratio of peak systolic velocity (S) to end-diastolic velocity (D) in the uterine artery waveform. It provides an estimate of downstream uterine vascular resistance and is influenced by the physiological state of the uterus, including the menstrual cycle, pregnancy status, and menopause.
Formula:
S/D ratio = Peak Systolic Velocity (S) ÷ End-Diastolic Velocity (D)
What it measures:
The uterine arteries supply blood to the uterus and endometrium. In the non-pregnant state, uterine vascular resistance is relatively higher than during normal pregnancy. Consequently, the end-diastolic velocity is relatively lower and the S/D ratio is comparatively higher.
During normal pregnancy, progressive trophoblastic invasion and remodeling of the spiral arteries produce a marked reduction in uteroplacental vascular resistance. This results in increased diastolic flow and a lower S/D ratio. Therefore, S/D values from a non-pregnant uterus should not be interpreted using pregnancy-specific reference ranges.
Non-Pregnant Uterine Artery:
• Uterine artery vascular resistance is relatively high.
• End-diastolic flow is present but comparatively reduced.
• A diastolic notch may normally be present, particularly before pregnancy and in higher-resistance states.
• S/D ratio is generally higher than that observed during normal pregnancy.
• Interpretation should consider the woman's age, menstrual status, menopausal status and clinical indication.
Measuring technique for S/D:
1. Identify the uterine artery near its crossing with the internal iliac artery/external iliac artery region according to the examination protocol.
2. Use color Doppler to identify the uterine artery and confirm its characteristic pulsatile arterial waveform.
3. Position the PW Doppler sample volume within the uterine artery, avoiding adjacent vessels.
4. Maintain an appropriate Doppler angle; for velocity measurements, keep the angle as close to 0° as practical.
5. Record the waveform during a period of minimal patient movement.
6. Obtain at least 3 consecutive uniform waveforms for analysis.
7. Identify the peak systolic velocity (S) and end-diastolic velocity (D).
8. Calculate the S/D ratio as S ÷ D.
9. Record the right and left uterine artery separately; do not assume that one side represents the other.
10. If the waveform contains a prominent diastolic notch, document its presence because waveform morphology can provide additional information beyond the S/D ratio.
Important Interpretation:
The S/D ratio is a ratio-based index and can become very high when diastolic flow is very low. When the end-diastolic component is absent, the S/D ratio becomes difficult or impossible to interpret reliably. When diastolic flow is reversed, S/D is not an appropriate index for describing the waveform. Current Doppler guidance generally favors PI over S/D or RI when assessing uterine artery waveform resistance because PI has a more linear relationship with vascular resistance. :contentReference[oaicite:1]{index=1}
Reference Values – Non-Pregnant Uterine Artery S/D Ratio
| Physiological State | Typical S/D Pattern | Waveform Characteristics |
| Non-pregnant / reproductive age | Relatively high | Higher resistance; diastolic notch may be present |
| Peri-/postmenopausal | Often higher | Higher resistance and relatively reduced diastolic flow |
| Normal pregnancy | Decreases | Progressive reduction in resistance and increased diastolic flow |
Clinical Note:
There is no single universally accepted S/D cutoff for all non-pregnant women. Uterine artery Doppler indices vary according to age, hormonal status, menstrual cycle and measurement technique. Therefore, S/D should be interpreted together with the RI, PI, waveform morphology and clinical indication rather than using an isolated numerical cutoff. Studies of uterine artery Doppler have demonstrated substantial physiological variation between individuals and between the placental and non-placental sides during pregnancy. :contentReference[oaicite:2]{index=2}
RI → RI (Resistance Index) is a Doppler-derived index used to estimate downstream arterial vascular resistance. In the uterine artery, RI reflects the relationship between peak systolic and end-diastolic blood-flow velocities and is influenced by uterine vascular tone, hormonal status and the physiological state of the uterus.
Formula:
RI = (Peak Systolic Velocity − End-Diastolic Velocity) ÷ Peak Systolic Velocity
What it measures:
The uterine artery supplies blood to the uterus and endometrium. In the non-pregnant state, uterine vascular resistance is relatively high compared with pregnancy. Consequently, the end-diastolic velocity is relatively reduced and the RI is generally higher.
During pregnancy, progressive remodeling of the uteroplacental circulation produces a marked reduction in vascular resistance. Diastolic flow therefore increases and the uterine artery RI decreases. Non-pregnant uterine artery RI should therefore not be interpreted using pregnancy-specific reference ranges.
Non-Pregnant Uterine Artery RI:
• Relatively high resistance waveform compared with pregnancy.
• End-diastolic flow is present but relatively reduced.
• An early diastolic notch may normally be present.
• RI may vary with the menstrual cycle and hormonal status.
• RI should be interpreted together with PI, S/D ratio and waveform morphology.
Measuring technique for RI:
1. Identify the uterine artery using gray-scale and color Doppler imaging.
2. Use color Doppler to confirm the characteristic pulsatile arterial waveform.
3. Place the PW Doppler sample volume within the uterine artery, avoiding adjacent vessels.
4. Maintain an appropriate Doppler insonation angle and obtain a clean spectral waveform.
5. Record the waveform during a period of minimal patient movement.
6. Obtain at least 3 consecutive uniform waveforms.
7. Identify the peak systolic velocity (S) and end-diastolic velocity (D).
8. Calculate RI as (S − D) ÷ S.
9. Measure the right and left uterine arteries separately and document both values.
10. Note the presence or absence of an early diastolic notch because waveform morphology provides additional information about uterine arterial resistance.
Physiological Variation:
Uterine artery RI is not completely constant in non-pregnant women. Studies have demonstrated variation during the menstrual cycle. One Doppler study reported uterine artery RI values of approximately 0.43 during the follicular phase, 0.50 around ovulation and 0.41 during the luteal phase, illustrating that cycle-related differences can occur depending on the population and measurement technique. :contentReference[oaicite:1]{index=1} Other studies have reported substantially higher RI values in non-pregnant women, demonstrating the importance of sampling site, technique, population and menstrual/hormonal status when comparing reference values. :contentReference[oaicite:2]{index=2}
Reference Values – Non-Pregnant Uterine Artery RI
| Physiological State | RI Pattern | Typical Waveform |
| Non-pregnant uterus | Relatively high | High-resistance waveform; reduced diastolic flow |
| Follicular phase | Variable | Relatively higher resistance may be observed |
| Periovulatory phase | May decrease | Increased uterine perfusion may reduce resistance |
| Luteal phase | Variable | Increased endometrial/uterine perfusion |
Clinical Interpretation:
A higher RI generally indicates greater downstream arterial resistance and relatively reduced diastolic flow. A lower RI indicates lower downstream resistance and relatively greater diastolic flow.
However, there is no single universally accepted RI cutoff for all non-pregnant women. RI varies with menstrual phase, hormonal status, age, sampling location and Doppler technique. Therefore, an isolated RI value should not be used to diagnose uterine pathology.
A 2026 study of uterine artery Doppler reported a mean RI of approximately 0.77 in the nongravid uterus, providing a useful contemporary population reference, but this should not be treated as a universal diagnostic cutoff. :contentReference[oaicite:3]{index=3} Reporting Recommendation:
Right uterine artery RI: ______
Left uterine artery RI: ______
Mean RI: ______
Diastolic notch: Present / Absent
PI → PI (Pulsatility Index) is a Doppler-derived index that describes the pulsatility of blood flow within the uterine artery. It reflects downstream vascular impedance and is particularly useful for assessing changes in uterine arterial resistance.
Formula:
PI = (Peak Systolic Velocity − End-Diastolic Velocity) ÷ Mean Velocity
What it measures:
The uterine arteries supply blood to the uterus and endometrium. In the non-pregnant state, uterine vascular resistance is generally higher than during normal pregnancy. Consequently, the uterine artery waveform usually demonstrates relatively reduced diastolic flow and a higher PI.
During pregnancy, progressive remodeling of the uteroplacental circulation produces a substantial reduction in vascular resistance. Diastolic flow increases and the uterine artery PI progressively decreases. Therefore, non-pregnant uterine artery PI should not be interpreted using gestational-age-specific pregnancy reference charts.
Non-Pregnant Uterine Artery PI:
• PI is generally higher than in normal pregnancy.
• Higher PI indicates greater downstream vascular impedance.
• Lower PI indicates relatively greater diastolic flow and lower vascular impedance.
• A protodiastolic notch may be present in the non-pregnant state.
• PI may vary according to age, hormonal status, menstrual phase and Doppler technique.
• Right and left uterine arteries should preferably be measured separately.
Measuring technique for PI:
1. Identify the uterine artery using gray-scale and color Doppler imaging.
2. Follow the uterine artery to an appropriate standardized measurement site according to the examination protocol.
3. Use color Doppler to confirm the arterial vessel and its pulsatile waveform.
4. Place the PW Doppler sample volume within the uterine artery, avoiding adjacent vessels.
5. Record several consecutive uniform cardiac cycles during minimal patient movement.
6. Identify the peak systolic velocity (S), end-diastolic velocity (D) and the mean velocity of the waveform.
7. Calculate PI as (S − D) ÷ Mean Velocity.
8. Obtain measurements from both the right and left uterine arteries.
9. If bilateral measurements are obtained, report the individual values and, where appropriate, the mean uterine artery PI.
10. Document the presence or absence of a diastolic notch because waveform morphology provides complementary information.
Reference Values – Non-Pregnant Uterine Artery PI:
Published nongravid reference values vary considerably between studies because of differences in population, ultrasound approach, sampling site and measurement methodology. A recent 2026 multicenter study involving nongravid women reported a mean uterine artery PI of approximately 2.07. :contentReference[oaicite:1]{index=1} An earlier study of 26 non-pregnant women reported a mean PI of 3.25 ± 0.83, with a calculated 95% reference range of approximately 1.21–5.29. :contentReference[oaicite:2]{index=2} Another study of non-pregnant women demonstrated mean PI values of approximately 2.30 in the follicular phase, 2.51 around ovulation and 2.50 in the mid-luteal phase, illustrating that physiological variation can occur across the menstrual cycle. :contentReference[oaicite:3]{index=3}
Suggested Reference Summary – Nongravid Uterine Artery PI
| Parameter | Reference / Observation |
| Recent nongravid reference | Mean PI ≈ 2.07 |
| Older nongravid study | Mean PI ≈ 3.25 ± 0.83 |
| Older 95% reference range | Approximately 1.21–5.29 |
| Clinical interpretation | Interpret with age, hormonal/menstrual status, technique and waveform morphology |
Clinical Interpretation:
A high PI indicates increased downstream uterine arterial impedance and relatively reduced diastolic blood flow. A low PI indicates lower impedance and relatively greater diastolic flow.
In the non-pregnant uterus, an elevated PI alone should not be considered diagnostic of uterine pathology because normal values show substantial inter-individual and methodological variation. PI should be interpreted together with RI, S/D ratio, waveform morphology, menstrual/hormonal status and the clinical indication.
The transition from the nongravid state to pregnancy is characterized by a substantial reduction in uterine artery PI as uteroplacental vascular resistance falls. A recent 2026 study demonstrated this progressive reduction in PI from the nongravid state through pregnancy. :contentReference[oaicite:4]{index=4} Reporting Recommendation:
Right uterine artery PI: ______
Left uterine artery PI: ______
Mean uterine artery PI: ______
Diastolic notch: Present / Absent
PSV → PSV (Peak Systolic Velocity) is the maximum blood-flow velocity recorded during systole in the uterine artery waveform. It represents the highest forward blood-flow velocity generated during ventricular contraction and can provide information about uterine arterial blood-flow dynamics.
Definition:
PSV = Maximum systolic blood-flow velocity measured during one cardiac cycle
What it measures:
The uterine arteries supply blood to the uterus and endometrium. In the non-pregnant state, uterine arterial blood flow is influenced by age, menstrual phase, hormonal status and vascular resistance. PSV therefore represents the peak velocity of arterial blood flow but should not be interpreted independently as a direct measure of vascular resistance.
Unlike PI, RI and S/D, PSV is an absolute velocity measurement and is strongly affected by the Doppler insonation angle, sample location, vessel diameter, cardiac output and technical settings.
Non-Pregnant Uterine Artery PSV:
• Represents the maximum systolic velocity in the uterine artery.
• PSV may vary considerably between individuals.
• Values may change with the menstrual cycle and hormonal status.
• PSV generally increases when uterine blood flow increases.
• PSV should be interpreted together with EDV, RI, PI and S/D ratio.
• Right and left uterine artery PSV should preferably be recorded separately.
Measuring technique for PSV:
1. Identify the uterine artery using gray-scale and color Doppler.
2. Follow the artery to a standardized measurement location according to the examination protocol.
3. Place the PW Doppler sample volume within the uterine artery.
4. Use an appropriate Doppler angle and apply angle correction for velocity measurement.
5. Keep the Doppler angle preferably ≤60° when technically possible.
6. Obtain several consecutive, uniform waveforms during minimal patient movement.
7. Identify the highest point of the systolic waveform as the Peak Systolic Velocity (PSV).
8. Record the velocity in cm/s.
9. Measure both right and left uterine arteries separately.
10. Avoid measuring during significant patient movement, vessel compression or an unstable waveform.
Important Technical Point:
Because PSV is an absolute velocity measurement, angle correction is essential. Unlike ratio-based indices such as RI and S/D, PSV cannot be reliably compared between examinations when substantially different Doppler angles are used.
Reference – Non-Pregnant Uterine Artery PSV
| Parameter | Interpretation |
| PSV | Peak systolic velocity of the uterine artery, reported in cm/s |
| Normal nongravid state | Variable; influenced by age, menstrual phase, hormonal status and measurement technique |
| Clinical use | Assessment of uterine arterial blood-flow velocity |
Clinical Interpretation:
A higher PSV indicates a greater peak systolic blood-flow velocity at the site of measurement, whereas a lower PSV indicates a lower peak systolic velocity. However, PSV alone does not directly quantify vascular resistance.
PSV should therefore be assessed together with RI, PI, S/D ratio and EDV. A change in PSV between examinations may also result from differences in Doppler angle, sample location, machine settings or cardiac output rather than a true change in uterine vascular physiology.
Reporting Recommendation:
Right uterine artery PSV: ______ cm/s
Left uterine artery PSV: ______ cm/s
Mean PSV: ______ cm/s
Doppler angle: ______°
EDV → EDV (End-Diastolic Velocity) is the blood-flow velocity measured at the end of diastole, immediately before the next systolic cardiac cycle. It represents the amount of forward blood flow that continues through the uterine artery during diastole and provides useful information about downstream vascular resistance.
Definition:
EDV = Blood-flow velocity measured at the end of diastole
What it measures:
The uterine artery supplies blood to the uterus and endometrium. In the non-pregnant state, uterine vascular resistance is generally higher than during normal pregnancy. Consequently, end-diastolic flow may be relatively reduced and the waveform may demonstrate a prominent diastolic notch.
When downstream vascular resistance decreases, more blood continues to flow during diastole and the EDV increases. When downstream resistance increases, diastolic flow decreases and the EDV falls.
EDV is therefore an important component of the RI, PI and S/D ratio calculations.
Relationship with Doppler indices:
• RI: RI = (PSV − EDV) ÷ PSV
• S/D: S/D = PSV ÷ EDV
• PI: PI = (PSV − EDV) ÷ Mean Velocity
A decrease in EDV generally causes RI and S/D to increase, while increased diastolic flow generally causes these indices to decrease.
Non-Pregnant Uterine Artery EDV:
• EDV is the end-diastolic component of the uterine artery waveform.
• It is usually lower than the PSV.
• EDV is influenced by uterine vascular resistance.
• EDV may vary with menstrual cycle, age and hormonal status.
• A prominent diastolic notch may be associated with relatively reduced diastolic flow.
• EDV should be interpreted together with PSV, RI, PI and S/D ratio.
• Right and left uterine artery EDV should preferably be documented separately.
Measuring technique for EDV:
1. Identify the uterine artery using gray-scale and color Doppler.
2. Place the PW Doppler sample volume within the uterine artery at the standardized examination site.
3. Obtain a clean spectral Doppler waveform with several consecutive uniform cardiac cycles.
4. Minimize patient movement and avoid vessel compression.
5. Identify the end-diastolic point immediately before the beginning of the next systolic upstroke.
6. Place the Doppler measurement cursor at the end-diastolic velocity point.
7. Record EDV in cm/s.
8. Measure both right and left uterine arteries separately.
9. Use the same sampling location and technical settings when comparing serial examinations.
Important Technical Point:
Because EDV is an absolute velocity measurement, the Doppler insonation angle affects the measured value. Appropriate angle correction should therefore be used for velocity measurements, preferably maintaining an angle of ≤60° when technically achievable.
Reference – Non-Pregnant Uterine Artery EDV
| Parameter | Interpretation |
| EDV | End-diastolic blood-flow velocity of the uterine artery, reported in cm/s |
| Higher EDV | Greater forward diastolic flow and generally lower downstream vascular resistance |
| Lower EDV | Reduced diastolic flow and generally higher downstream vascular resistance |
| Nongravid uterus | Variable according to age, menstrual phase, hormonal status and Doppler technique |
Clinical Interpretation:
A higher EDV indicates greater forward blood flow during diastole and generally corresponds to lower downstream vascular impedance. A lower EDV indicates reduced diastolic flow and generally corresponds to higher vascular impedance.
In the non-pregnant uterus, EDV should not be interpreted using pregnancy-specific reference ranges. There is considerable physiological variation, and EDV is strongly influenced by Doppler technique and insonation angle.
An isolated EDV value should therefore not be used to diagnose uterine pathology. It should be interpreted together with PSV, RI, PI, S/D ratio, waveform morphology and the clinical indication.
Reporting Recommendation:
Right uterine artery EDV: ______ cm/s
Left uterine artery EDV: ______ cm/s
Mean EDV: ______ cm/s
Diastolic notch: Present / Absent
Mean Velocity → Mean Velocity is the average blood-flow velocity calculated across the entire Doppler waveform during one cardiac cycle. In uterine artery Doppler, it represents the average velocity of blood flow throughout systole and diastole and is used in the calculation of the Pulsatility Index (PI).
Definition:
Mean Velocity = Average velocity of blood flow over the cardiac cycle
What it measures:
The uterine artery waveform contains periods of rapid systolic flow followed by lower-velocity diastolic flow. Mean velocity provides an estimate of the overall average blood-flow velocity during the measured cardiac cycle.
Unlike PSV and EDV, which represent specific points on the waveform, mean velocity incorporates the velocity throughout the cardiac cycle and is therefore particularly important for calculating the PI.
Relationship with PI:
PI = (Peak Systolic Velocity − End-Diastolic Velocity) ÷ Mean Velocity
Therefore, accurate determination of mean velocity is important when calculating the uterine artery PI.
Non-Pregnant Uterine Artery Mean Velocity:
• Represents the average blood-flow velocity throughout the cardiac cycle.
• Includes both systolic and diastolic blood-flow components.
• Is influenced by uterine vascular resistance and overall blood-flow conditions.
• May vary with age, menstrual phase, hormonal status and cardiac output.
• Is affected by the Doppler sampling site and technical parameters.
• Should not be interpreted as an isolated diagnostic parameter.
Measuring technique for Mean Velocity:
1. Identify the uterine artery using gray-scale and color Doppler.
2. Place the PW Doppler sample volume within the uterine artery at the standardized measurement site.
3. Obtain a stable spectral Doppler waveform containing several consecutive uniform cardiac cycles.
4. Minimize patient movement and avoid excessive pressure over the vessel.
5. Ensure an appropriate Doppler angle and use angle correction for absolute velocity measurements.
6. Record at least 3 similar consecutive waveforms.
7. Use the ultrasound system's automated waveform analysis, when available, to calculate the mean velocity over the cardiac cycle.
8. Confirm that the tracing is clean and that the automated contour accurately follows the waveform.
9. Measure the right and left uterine arteries separately.
10. Use the same technique and sampling location for serial examinations whenever possible.
Important Technical Point:
Mean velocity is an absolute velocity measurement. Therefore, measurement accuracy depends on Doppler angle, sample location, waveform quality and machine settings. For velocity measurements, an insonation angle of ≤60° is generally preferred when technically achievable.
Reference – Non-Pregnant Uterine Artery Mean Velocity
| Parameter | Interpretation |
| Mean velocity | Average blood-flow velocity throughout the cardiac cycle, reported in cm/s |
| Higher mean velocity | Indicates greater average blood-flow velocity at the sampled uterine artery |
| Lower mean velocity | Indicates lower average blood-flow velocity at the sampled site |
| Nongravid uterus | Variable according to age, menstrual phase, hormonal status, cardiac output and measurement technique |
Clinical Interpretation:
Mean velocity should primarily be regarded as a supporting Doppler measurement rather than an independent marker of uterine vascular resistance. A high or low mean velocity does not by itself establish normality or abnormality.
For assessment of uterine arterial impedance, PI, RI and S/D ratio are more directly useful. Mean velocity is particularly important because it forms the denominator of the PI calculation.
In the non-pregnant uterus, no single universally accepted reference range for mean uterine artery velocity applies to all women. Values can vary substantially according to measurement technique, vessel location, menstrual phase and physiological state.
Reporting Recommendation:
Right uterine artery Mean Velocity: ______ cm/s
Left uterine artery Mean Velocity: ______ cm/s
Mean bilateral velocity: ______ cm/s
Measurement site: ______
Diastolic Notch → Diastolic Notch is a transient decrease in blood-flow velocity seen immediately after peak systolic flow and before the continuation of diastolic flow in the uterine artery waveform. It reflects relatively increased downstream vascular impedance and is an important qualitative feature of uterine artery Doppler assessment.
What it represents:
A diastolic notch appears as a brief downward deflection or interruption in the early diastolic portion of the uterine artery waveform. It is associated with relatively higher downstream vascular resistance and reduced early-diastolic blood flow.
In the non-pregnant uterus, a diastolic notch may be a normal finding because uterine vascular resistance is generally higher than during normal pregnancy. Therefore, the presence of a notch in a non-pregnant woman should not automatically be considered abnormal.
Types of Diastolic Notch:
• Early diastolic notch: Brief reduction in velocity immediately following systole.
• Unilateral notch: Notch present in only one uterine artery.
• Bilateral notch: Notch present in both right and left uterine arteries.
• Prominent notch: Clearly visible reduction in early-diastolic flow.
• Absent notch: Smooth transition from systolic flow into diastolic flow without a distinct early-diastolic interruption.
Non-Pregnant Uterine Artery:
• A diastolic notch may normally be present.
• Its presence generally indicates relatively higher uterine arterial resistance.
• Notch morphology may vary with age, menstrual cycle and hormonal status.
• Bilateral or prominent notching does not independently diagnose uterine pathology.
• The notch should be interpreted together with PI, RI, S/D ratio and clinical findings.
How to Assess the Diastolic Notch:
1. Identify the uterine artery using color Doppler.
2. Obtain a stable spectral Doppler waveform using PW Doppler.
3. Record at least 3 consecutive uniform cardiac cycles.
4. Examine the early-diastolic portion of the waveform immediately after the systolic peak.
5. Identify any distinct temporary decrease in velocity before the diastolic flow continues.
6. Record the finding as Present or Absent.
7. Document whether the notch is right-sided, left-sided or bilateral.
8. When appropriate, describe the notch as mild, moderate or prominent based on its visual appearance.
9. Correlate the waveform appearance with PI, RI and S/D ratio.
Diastolic Notch – Non-Pregnant Uterine Artery
| Finding | Typical Interpretation |
| Notch absent | Smooth transition into diastolic flow; relatively lower early-diastolic impedance |
| Unilateral notch | Notch present in one uterine artery; interpret with the opposite side and quantitative indices |
| Bilateral notch | Notch present in both uterine arteries; may be a normal nongravid finding |
| Prominent notch | More pronounced early-diastolic reduction in flow; indicates relatively higher vascular impedance |
Clinical Interpretation:
The diastolic notch is a qualitative waveform feature rather than a numerical Doppler index. In a non-pregnant woman, the presence of a notch can be physiological and should not be interpreted in isolation.
The clinical significance of a notch becomes more important when it is considered together with quantitative Doppler indices such as PI, RI and S/D ratio. A prominent notch accompanied by elevated resistance indices may indicate increased uterine arterial impedance, but the overall interpretation depends on the clinical context.
Reporting Recommendation:
Right uterine artery: Notch Present / Absent
Left uterine artery: Notch Present / Absent
Notch: Unilateral / Bilateral
Prominence: Mild / Moderate / Prominent
Right PI: ______
Left PI: ______
No comments:
Post a Comment