To compare the labor epidural analgesic (EA) profiles between landmark insertion EA levels which are congruent and ingruent to ultrasound confirmation in lateral decubitus position.

Epidural analgesia is the mainstream method for labor analgesia. Landmark identification of L3 to L5 spinous process is most commonly applied for determination of epidural insertion. However, the precision of epidural catheter insertion site was affected by physiological and anatomical variations in pregnant women and positions such as sitting or lateral decubitus. Previous study showed the clinical estimation would be ≥ 1 vertebral level higher than the anatomical position determined by ultrasound at least 40% of the time in sitting position among western pregnant women. For asian parturients, epidural analgesia is commonly performed in lateral decubitus position because of smaller stature. In addition, it remains uncertain whether the landmark epidural insertion level congruent or ingruent is associated with different analgesia profiles such as the dosage requirement and the frequncy of adjustment.

Inclusion:

1. Normal spontaneous delivery parturients receiving labor epidural analgesia in first stage of labor
2. Using patient-controlled epidural analgesia

Exclusion:

1. who has an accidental epidural puncture
2. who receives epidural insertion by ultrasound identification
3. who uses of magnesium sulfate

Parturient who receive labor epidural