To compare the postoperative analgesic effect and the intensity of motor block in different concentration ropivacaine plus fentanyl when used epidurally with a patient-controlled analgesia device after Cesarean delivery.

1. Written informed consent must be obtained before any study specific procedures are undertaken.
2. All patients were received epidural anesthesia with 2% Lidocaine and patient-controlled epidural analgesia (PCEA) for post- operative pain control. PCEA randomly allocated into three groups. Group A patients received 0.08% ropivacaine plus 4 mcg /mL fentanyl, Group B patients received 0.08% ropivacaine plus 2mcg /mL fentanyl, and Group C patients received 0.16 % ropivacaine plus 2 mcg /mL fentanyl. Dermographic data, dosage of PCEA during first 48 hours post-operation，NRS scores, patient satisfaction and the intensity of motor block will be recorded and analyzed.

Inclusion Criteria:

• Female undergoing elective Cesarean delivery and receive patient-controlled epidural analgesia

Exclusion Criteria:

• With the comorbidity of chronic heart, lung, liver and renal disease, chronic alcoholism, allergy to ropivacaine, poor epidural function and combine other anesthesia method

Only include pregnant female receiving elective Cesarean delivery and post-operative epidural analgesia

Participant do not know which formula they are receive. Nor do the daily care providers.