It is critical that the exact gestational age of a newborn baby, especially premature baby, be determined to evaluate the status of a disease and its management and to estimate the prognosis of a patient. This study aimed to investigate an easy and accurate method to estimate gestational age on cranial ultrasound, requiring minimal additional time and equipment.

A high-resolution coronal sonographic image was obtained via the anterior fontanel with a 5-12 Mhz linear probe after the usual cranial sonographic examination. We measured the depth of cerebral hemisphere, thickness of corpus callosum, and depth of cingulate sulcus and obtained the correlations between these factors and gestational age.

Depth of cingulate sulcus had the highest correlation coefficiency with gestational age (r=0.878, P =0.000). All the cases, except for 2 cases, had a gestational age of more than 37 weeks, when the depths of cingulate sulcus were more than 0.55 cm, and had a gestational age less than 34 weeks, when the depths of cingulate sulcus were less than 0.35 cm.

Measurement of the depth of cingulate sulcus was a simple and accurate method to estimate the gestational age on cranial ultrasound. The gestational age is more than 37 weeks, when the depth of cingulate sulcus is more than 0.55 cm, and is less than 34 weeks, when the depth of cingulate sulcus is less than 0.35 cm.