A prospective ultrasound study was conducted in 160 normal pregnant women with gestational ages ranging from 14 to 40 weeks. Several fetal biometric measurements were obtained, including the posterior horn width (PHW) and the cerebroposterior horn distance (CPHD) of the lateral ventricles. Curvilinear relationships were found between the gestational age and the ratio of the PHW/CPHD (r = 0.665, p less than 0.0001); and the PHW/hemispheric width (HW), (r = 0.716, p less than 0.0001) and also between the biparietal diameter and the PHW/CPHD ratio (r = 0.649, p less than 0.0001), and the PHW/HW ratio (r = 0.732, p less than 0.0001). A correlation in growth was also observed between the femur length and the PHW/CPHD (r = 0.660, p less than 0.0001), and the PHW/HW (r = 0.734, p less than 0.0001). Nomograms of the PHW, CPHD, and the ratio of PHW/CPHD against gestational age were generated. The establishment of normal indices of the posterior horn provides new, precise, and comprehensive data that will serve as a standard against which the evaluation of early abnormal ventricular growth and anomalous development of the central nervous system may be compared.