Inclusion Criteria:  Parturient with normal vaginal delivery in late first stage of labor (cervical dilatation ≥ 6 cm by examination) Aged 18-40 years old Single, term pregnant with normal fetal heart rate Request neuroaxial analgesia  Exclusion Criteria:  Parturient who refuses to participate, American Society of Anesthesiologists (ASA) physical status >II, Body mass index more than 35 kg/m2 Severe pre-eclampsia or eclampsia Uncontrolled thyrotoxicosis Cardiovascular troubles (e.g. stenotic valvular heart disease or cardiomyopathy) Increased intracranial tension due to a space-occupying lesion Any contraindication to regional anesthesia such as local skin or soft tissue infection, coagulopathy or receiving anticoagulant therapy, thrombocytopenic, uncorrected hypovolemia, preexisting neurologic deficits, spinal deformity or previous spine surgery. Hypersensitivity to the study drugs Parturient who scheduled for emergency cesarean section due to fetal distress, antepartum hemorrhage, multiple gestation or fetal malpresentation