Discordant middle cerebral artery peak systolic velocity Doppler studies in a fetus with RhD alloimmunization

Doppler measurement of the fetal middle cerebral artery peak systolic velocity is a valuable tool in detecting the presence of fetal anemia in Rh-sensitized pregnancies. We present a case in which discordant left and right middle cerebral artery Dopplers complicated clinical management.

An RhD-alloimmunized patient had middle cerebral artery Dopplers at 30 weeks of gestation, which showed an elevated peak systolic velocity in the left middle cerebral artery, greater than 1.55 multiples of the mean, but the right middle cerebral artery was within the normal range. The amniotic fluid change in optical density at a wavelength of 450 nm was consistent with the right middle cerebral artery Doppler. When both Dopplers were greater than or equal to 1.5 multiples of the mean, fetal blood sampling revealed a hematocrit of 28%. Postnatal cranial ultrasound examination showed normal architecture, but there was persistent discordant Dopplers in the left versus the right middle cerebral artery.

Measurement of both left and right middle cerebral artery peak systolic velocities may identify patients with intrinsic variations in cranial blood vessels resulting in abnormal Doppler flows.