Transvaginal Doppler assessment of the fetal cerebral circulation.

Blood flow velocity waveforms were recorded by pulsed Doppler examination of the fetal internal carotid and middle cerebral arteries using the established transabdominal route as well as a new transvaginal approach. Fourteen normal controls and 11 pregnancies complicated by intrauterine growth retardation were studied. Satisfactory recordings were obtained in all 25 cases. There was a good correlation (R2 = 0.98) between pulsatility index (PI) values obtained transabdominally and transvaginally. The PI in the middle cerebral artery was significantly higher than in the internal carotid artery in both normal and growth-retarded fetuses. Pulsatility in both cerebral vessels was significantly decreased in growth-retarded fetuses when compared with normal controls. The transvaginal route, which produces a coronal section of the fetal brain, allows better distinction between the internal carotid and middle cerebral arteries. Furthermore, signals of equal quality are obtained from vessels in both cerebral hemispheres. Transvaginal scanning of the fetal cerebral arteries is a feasible technique offering an alternative to transabdominal scanning when the latter is hampered by technical difficulties.