Reference values for Doppler parameters of the fetal anterior cerebral artery throughout gestation

To construct normal reference values for Doppler parameters in 2 anatomical segments of the fetal anterior cerebral artery (ACA) throughout pregnancy.

The ACA was evaluated in 373 normally growing fetuses from 20 to 40 weeks of gestation. The first segment of the ACA (ACA-S1) was recorded just after its origin from the internal carotid artery in the same plane as the middle cerebral artery (MCA). The second segment (ACA-S2) was recorded distal to the outlet of the anterior communicating artery.

The ACA pulsatility index (PI) behaved similarly in both segments, with a constant increase until 28 weeks followed by a decrease until the end of pregnancy [ACA-S1 PI = 3.49 - 0.37 x gestational age (GA) - (0.0063 x GA(2)), SD = 0.6 - 0.061 x GA - (0.001 x GA(2)); ACA-S2 PI = 1.54 - 0.22 x GA - (0.0037 x GA(2)), SD = 0.206 + (0.0037 x GA)]. Peak systolic velocities in both segments showed a constant increase from 20 to 40 weeks of gestation. No significant differences were found between the 2 segments with regard to any Doppler parameter. However, the angle of insonation and the time spent on examination were significantly lower and reproducibility was better for ACA-S1.

Despite showing similar Doppler values, ACA-S1 has a higher reliability than ACA-S2 and can be recorded in the same anatomical projection as the MCA.