Abnormal dilatation of ventricles has been shown to be the most common abnormality of the brain & fetus in most of the geographical zones, but the normal dimension of the fetal lateral ventricle in south-south geopolitical zones of Nigeria has not been evaluated. The aim of this study was to determine the normal feto-lateral ventricular diameter using ultrasound at different gestational ages. Measurement of the fetal-lateral ventricular diameter was obtained from 685 fetuses of pregnant mothers that met the inclusion criteria during routine ultrasound scan in Calabar metropolis. Measurement of the ventricular diameter was taken at the level of the atria, measured according to Australian society for ultrasound in medicine guidelines. Udoh et al.; JAMMR, 30(1): 1-5, 2019; Article no.JAMMR.34770 2 Original Research ArticleThe result shows that the mean lateral ventricular diameter of fetuses in the studied region is 6.62 ± 2.51 mm with a range of 4.12-9.54 mm. The lateral ventricular diameter and the fetal head circumferences, as well as the gestational age, do not show any significant correlation throughout gestation. Conclusion: Fetuses in Calabar Metropolis have a lateral ventricular diameter that ranges from 4.12 -9.54 mm. Ventricular diameter above this normal range in this region and could be considered as an abnormal and may demand further investigations.