 Sample size was based on previous literature by WANG et al comparing Real-time Ultrasound-assisted And Non-ultrasound-assisted Approach in combined spinal-epidural puncture obese patient. Sample size was calculated for primary outcome 1 success rate of spinle needle insertion and 2 success rate of single needle pass, and secondary outcome 1 duration for successful dural puncture and duration for procedure. The largest sample size was taken. 