Nomogram of fetal middle cerebral artery peak systolic velocity at 23-35 weeks of gestation in a Brazilian population: pilot study.

Objective: To establish normative data for the peak systolic velocity of the middle cerebral artery (MCA-PSV) of fetuses in the second half of pregnancy using multiples of the median and percentile reference range.
Methods: A cross-sectional study was performed in 90 healthy fetuses at between 23 and 35 weeks of gestation. A bi-dimensional axial scan of the brain, including the thalami and cavitas septi pellucidi was obtained. The circle of Willis was visualized using color flow mapping. Pulsed-wave Doppler velocimetry of the MCA was performed close to the artery's origin, with a beam-vessel angle below 20 degrees . A table with the multiples of the median (MoM) of the MCA-PSV for each gestational age was generated and Pearson's correlation coefficient (r) was calculated. Regression modeling across gestational age was performed to obtain the reference values.
Results: There was a strong correlation between the MCA-PVS and gestational age (r = 0.70; p < 0.001). Values for the MCA-PSV for the following MoM were calculated: 1.0, 1.29, 1.50, and 1.55. The MCA-PSV 2.5(th) and 97.5(th) centiles ranged from 24.33 cm(2)/s to 78.36 cm(2)/s, respectively, between weeks 23 and 35.
Conclusions: A nomogram for the fetal MCA-PSV during the second half of pregnancy was generated.