Objective: The aim of this study was to determine the clinical significance of slightly lateral ventricular enlargement. Methods: We examined 1151 infants with a gestational age of 36 weeks or greater. We assessed for the presence of ventricular enlargement when apparent space was observed in the frontal horn or body of lateral ventricle by a transfontanel ultrasound scan. Results: Two hundred and forty-eight infants had ventricular enlargement. The atrial widths in most infants were less than 10mm. Ventricular enlargement correlated with Cesarean delivery, gestational age, birth weight, respiratory disturbance at delivery and respiratory inhibition after crying (RIAC). Ventricular enlargement could be divided into three types by ultrasound findings. Forty-five infants showed only enlargement of the anterior horn (Type A), 97 infants showed enlargement from the body to the posterior horn (Type B), and 108 infants showed whole enlargement from the anterior to the posterior horn (Type C). The infants with Type A correlated with intrauterine growth restriction, placenta previa, male gender and birth weight. The infants with Type B correlated with cesarean delivery. The infants with Type C correlated with diabetes mellitus, respiratory disturbance at delivery, RIAC and feeding hypoxemia. Conclusions: Slightly lateral ventricular enlargement should be considered clinically significant.