The purpose of this study was to determine the growth of lateral ventriclar size of fetuses between 15 and 25 weeks of gestation. A prospective study of normal singleton pregnancies was evaluated consecutively. Measurement of the lateral ventricle was performed by transabdominal sonography as a part of routine obstetric examination in 338 fetuses. The mean size of the lateral ventricular atrial diameter for the 338 fetuses was 6.65 ± 0.95 mm. A weak correlation was found between gestational age and lateral ventricle width (R2 = 0.03, P < 0.001). In addition, there was a weak correlation between biparietal diameter and lateral ventricle width (R2 = 0.062, P < 0.001). The mean size was correlated with the others in the literature. The lateral ventricle size was stable across the second trimester. Since there was a weak correlation, and overlapping values throughout the gestation weeks, it seems clinically impractical to use a nomogram of the lateral ventricle size. However, a value of upper limit (10 mm) may be a clue for lateral ventricular dilatation, and close follow-up may be helpful. © 2012 - IOS Press and the authors.