The fetal cerebellar vermis: normal development as shown by transvaginal ultrasound

Objective-To determine the normal appearance and development of the fetal c erebellar vermis using midsagittal planes obtained by transvaginal sonograp hy. Subjects and Methods-A total of 101 fetuses were evaluated by transvaginal sonography between 21 and 39 weeks of gestation. The mid-sagittal antero-po sterior and cranio-caudal vermian diameters, circumference and surface area were measured and calculated. Nomograms were produced. Results-The vermis was observed in 96% of the cases and all the measurement s were performed in 92%. The vermis grows in a linear fashion throughout pr egnancy. The growth pattern correlates well with gestational age, biparieta l diameter, head circumference and transverse cerebellar diameter. Conclusion-Transvaginal sonography is a valuable tool in the study of the f etal vermis during the second half of pregnancy. Knowledge of its normal ap pearance may help identify developmental anomalies and enable accurate pren atal counseling. Copyright (C) 2001 John Wiley & Sons, Ltd.