Normal obstetric Doppler at 35 weeks

A case of normal obstetric Doppler at 35 weeks gestation:

1. Umbilical Artery (UA) Resistance Index (RI) = 0.6:

   - The Umbilical Artery carries  deoxygenated blood back to the placenta for oxygen exchange.

   - An RI of 0.6 suggests that there is moderate resistance to blood flow in the umbilical artery.

   - This value is within the normal range, indicating a healthy balance between oxygen and nutrient supply to the fetus.

2. Middle Cerebral Artery (MCA) Resistance Index (RI) = 0.7:

   - The Middle Cerebral Artery supplies blood to the brain, which is crucial for fetal neurological development.

   - An RI of 0.7 signifies mild resistance to blood flow in the MCA. This is normal. 

3. Uterine Artery (UtA) Resistance Index (RI) = 0.4:

   - The Uterine Artery supplies oxygen-rich blood to the uterus and the placenta.

   - An RI of 0.4 indicates low resistance in the uterine artery.

   - This low resistance is beneficial, as it ensures adequate blood supply to the placenta, supporting the needs of both the mother and the growing fetus.

4. Ductus Venosus Flow:

   - The Ductus Venosus is a fetal vessel that shunts oxygenated blood from the umbilical vein directly to the inferior vena cava, bypassing the liver.

   - Normal ductus venosus flow ensures efficient oxygen delivery to the developing fetus.

   - The absence of significant abnormalities in this flow pattern is a positive sign of fetal well-being.

In conclusion, Doppler measurements at 35 weeks gestation play a crucial role in evaluating the fetal circulatory system's health. 

Waveforms description in normal obstetric Doppler:

• Uterine artery: The uterine artery waveform should have a low-resistance pattern with continuous forward flow throughout diastole. This indicates that the placenta is well-vascularized and able to provide adequate oxygen and nutrients to the fetus.
• Middle cerebral artery: The middle cerebral artery waveform should have a high-resistance pattern with a sharp systolic peak and absent or minimal diastolic flow. This indicates that the brain is well-perfused and that the fetus is not experiencing any oxygen deprivation.
• Umbilical artery: The umbilical artery waveform should have a triphasic pattern with forward flow in systole, and forward flow again in late diastole. This indicates that the placenta is functioning normally and that the fetus is receiving adequate oxygen and nutrients.
• Ductus venosus: The ductus venosus waveform should have a continuous forward flow with no reversal of flow. This indicates that the fetus is not experiencing any significant hemodynamic compromise.

Here are some of the abnormal waveforms that may be seen in late 3rd trimester pregnancy:

• Uterine artery: A high-resistance uterine artery waveform may indicate that the placenta is not well-vascularized and that the fetus is at risk for growth restriction.
• Middle cerebral artery: A low-resistance middle cerebral artery waveform may indicate that the brain is not receiving adequate oxygen and nutrients. This can be a sign of fetal distress.
• Umbilical artery: An absent or reversed diastolic flow in the umbilical artery is a sign of fetal compromise. This can be caused by a number of factors, including placental insufficiency, preeclampsia, or intrauterine growth restriction.
• Ductus venosus: A reversal of flow in the ductus venosus is a sign of severe fetal compromise. This is a medical emergency and the fetus will need to be delivered as soon as possible.

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Doppler in pregnancy