The cerebroumbilical ratio (also called the cerebroplacental ratio) can be used to evaluate a fetus.

Analysis: Doppler ultrasound (based on a trace of at least consecutive waveforms, in the absence of fetal breathing movements and in the absence of uterine contractions, with the angle of insonation less than 30 degrees.



(1) pulsatility index of the middle cerebral artery (MCA)

(2) pulsatility index of the umbilical artery (UA)


cerebroumbilical ratio =

= (pulsatility index of MCA) / (pulsatility index of UA)



• The mean UA PI for the cohort reported by Prior et al was 0.80 while the MCA PI was 1.37. The mean ratio for the cohort was 1.77.

• Normally the ratio peaks at the 34 week of gestation then slowly declines.

• A fetus with a ratio less than the 10th percentile for gestational age is at increased risk for fetal compromise.

• A ratio > 90th percentile excludes fetal compromise with Cesarean section.

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