 The failure in indwelling epidural catheter for a parturient might cause an anesthetic difficulty. Furthermore, no one can predict the accuracy of needle placement prior to skin puncture with any of landmark-based technique. This may result in multiple trying attempts at needle puncture, pain and discomforts of patients and poor patient satisfaction. The aim of this study was to explore the difference of epidural space between parturient and non-pregnant women by assessing ultrasound image. 