Fetal and neonatal cerebral blood velocity in the normal fetus and neonate: a longitudinal Doppler ultrasound study.

In a longitudinal Doppler ultrasound study fetal and early neonatal cerebral blood flow velocities were assessed in the middle cerebral artery in 40 uncomplicated pregnancies during the third trimester of pregnancy and in 22 neonates born from these pregnancies. Peak systolic (PSFV), temporal mean (TMFV), and end diastolic flow velocities (EDFV) were determined and pulsatility index (PI = (PSFV - EDFV)/TMFV) and Pourcelot's resistance index (RI = (PSFV - EDFV)/PSFV) calculated. PSFV, TMFV and EDFV increased during the third trimester of pregnancy and were significantly higher from 36 weeks of gestation onward as compared to values obtained at 28 weeks of gestation, suggesting an increase in actual cerebral blood flow. PI and RI of the MCA did not differ significantly during this period. Immediately after birth PSFV, TMFV and EDFV decreased significantly and remained lower during the first 5 postnatal days compared to fetal values. PI and RI of the MCA tended to decrease during the first postnatal day, but stabilized afterwards.