An S/D ratio greater than 3.0 on umbilical artery Doppler indicates what?

An S/D ratio greater than 3.0 on umbilical artery Doppler indicates what?

• A. Normal placental function
• B. Uteroplacental insufficiency
• C. Fetal anemia
• D. Fetal tachycardia

Answer: (B)

An elevated S/D ratio in the umbilical artery Doppler means the placenta is showing higher vascular resistance, indicating impaired placental perfusion. When placental blood flow resistance increases, diastolic flow diminishes while systolic flow remains, so the ratio goes up. A ratio above about 3.0 is considered abnormal and points to uteroplacental insufficiency, which raises the risk of fetal hypoxia and growth restriction. This pattern aligns with placental disease such as preeclampsia or chronic hypertension. It’s not a sign of normal placental function, which would have preserved diastolic flow and a lower S/D ratio. It isn’t typically seen with fetal anemia (which tends to lower the S/D ratio due to increased fetal cardiac output) or fetal tachycardia (a heart rate issue, not a Doppler resistance finding). In severe insufficiency, absent or reversed end-diastolic flow can occur, signaling heightened risk.

An elevated S/D ratio in the umbilical artery Doppler means the placenta is showing higher vascular resistance, indicating impaired placental perfusion. When placental blood flow resistance increases, diastolic flow diminishes while systolic flow remains, so the ratio goes up. A ratio above about 3.0 is considered abnormal and points to uteroplacental insufficiency, which raises the risk of fetal hypoxia and growth restriction. This pattern aligns with placental disease such as preeclampsia or chronic hypertension. It’s not a sign of normal placental function, which would have preserved diastolic flow and a lower S/D ratio. It isn’t typically seen with fetal anemia (which tends to lower the S/D ratio due to increased fetal cardiac output) or fetal tachycardia (a heart rate issue, not a Doppler resistance finding). In severe insufficiency, absent or reversed end-diastolic flow can occur, signaling heightened risk.