Second trimester screening for the basilar artery: a new approach using slowflowHD.

Objectives: Sonographic evaluation of the basilar artery is challenging, and a limited number of reports are available about the prenatal period, as manual positioning of probes is technically difficult. The objective of this study was to describe a sonographic transabdominal approach based on slowflow HD for screening of the basilar artery during the second trimester scan.

Methods: A total of 49 women who were enrolled in a second trimester screening were included when the fetus was in the occipitoanterior position. Dopper screening of the cerebral artery was performed, which revealed the "Y" sign indicating the basilar trunk arising from two vertebral arteries in the axial oblique view when the probe was located around the junction of the vertebral processes and occipital bone and was superior to the first vertebral body, sloping slightly to the cephalic side. The Doppler ultrasound probe was placed perpendicular to the basilar artery. The flow direction was below the baseline, away from the probe in the basilar artery, consistent with a caudocephalic orientation. Peak systolic and diastolic velocities were measured.

Results: The basilar artery was identified in all 49 fetuses, with a mean gestational age of 22 weeks (range 20 to 26 weeks). The mean peak systolic velocity of the basilar artery was 15.8 cm/second (range 9.12-26.44 cm/second). There was a slight increase in peak systolic velocity according to the gestational age of the fetus.

Conclusions: This study demonstrated that evaluation of the basilar artery can be performed during the second trimester a new transabdominal approach involving slowflow HD.