3.2. Data Collection

Fetal vermian diameters were obtained during the routine ultrasound examinations which were performed either to rule out fetal anomalies or for the fetal follow-up between 17 and 30 weeks of gestation with a Logic 5 Pro (general electric health care, Milwaukee, USA) ultrasound machine by using a 5 MHz curvilinear transducer. Each patient was examined by one examiner (C.G) in order to eliminate interobserver variability. Measurements were performed on a median slice for demonstration of the vermis, brainstem, fourth ventricle, and cisterna magna (Figure 1). Each measurement was performed at least twice and the average of the two values was noted. Craniocaudal (CC) diameter was measured from the culmen superiorly to the uvula inferiorly, and the anteroposterior (AP) diameter from the central lobule anteriorly to the tuber posteriorly (10).