Fetal intracranial arterial hemodynamics assessed by color and pulsed Doppler ultrasound.

Fetal intracranial arterial velocimetries were serially performed on 31 pregnant women with regular menstrual cycle, at 28-40 weeks of gestation, using color and pulsed Doppler ultrasound. The change in fetal intracranial arterial hemodynamics was based on the calculation of resistance index (RI). There was no significant difference between the RI values in the anterior cerebral artery (ACA) and middle cerebral artery (MCA) from 28 weeks to term. The RI in the posterior cerebral artery (PCA) was significantly lower than that in the ACA and MCA, respectively, from 28 weeks to term (P less than 0.001). The PI values in both the ACA and MCA remained unchanged from 28 to 33 weeks, became significantly lower from 34 to 35 weeks (P less than 0.05), and the values were fairly constant thereafter. The RI seen in the PCA showed no significant change from 28 weeks to term. This color and pulsed Doppler ultrasound assessment of fetal intracranial arterial blood flow provides a useful foundation for elucidating normal intracranial hemodynamics and will aid in avoiding misinterpretations of the different intracranial arteries.