Umbilical Artery Doppler PI, S/D Ratio, and RI Calculator

Calculate umbilical artery pulsatility index (PI), systolic/diastolic (S/D) ratio, and resistance index (RI) from waveform measurements. Interprets absent or reversed end-diastolic flow (AEDF/REDF) in fetal growth restriction.

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Clinical Guidance

BMI is a screening measure of body size, not a direct measure of body fat. The standard WHO categories are underweight (<18.5), normal (18.5–24.9), overweight (25–29.9), and obese (≥30).

BMI can overestimate body fat in athletes with high muscle mass and underestimate it in older adults with low muscle mass. Interpret it alongside waist circumference and clinical context rather than as a standalone diagnosis.

⚕ Clinical Disclaimer: These calculators are for educational and reference purposes only. Always verify results with qualified clinical judgment and current clinical guidelines. Do not use as a sole basis for medical decisions.
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How It Works

Calculate umbilical artery pulsatility index (PI), systolic/diastolic (S/D) ratio, and resistance index (RI) from waveform measurements. Interprets absent or reversed end-diastolic flow (AEDF/REDF) in fetal growth restriction

Each component has a specific meaning:

  • Waveform measurements — The waveform measurements recorded for the scenario being assessed.

Note: Interpret the umbilical artery doppler result against the thresholds and context described above.

How to Use

Enter the waveform measurements for the scenario you are assessing. Calculate umbilical artery pulsatility index (PI), systolic/diastolic (S/D) ratio, and resistance index (RI) from waveform measurements. Interprets absent or reversed end-diastolic flow (AEDF/REDF) in fetal growth restriction. Use the umbilical artery doppler result to inform your calculation.

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Frequently Asked Questions