Subarachnoid block is a widely used anesthetic technique for cesarean section. To improve the quality of analgesia and prolong its duration, the addition of intrathecal opioids to local anesthetics has been encouraged.

In a double blind randomized controlled trial, 60 parturient women ASA 2-3 scheduled for elective cesarean delivery under spinal anesthesia will be randomly divided into 2 groups: Group 1 will receive sufentanil 5 μg and Group 2 will receive meperidine 12.5 mg. In every group, 0.5% heavy bupivacaine 10 will be added.

A questionnaire will be used to collect data. Patients' demographic and operative characteristics will be recorded. These include block level, heart rate, mean arterial pressure, nausea, vomiting, shivering and use of vasopressors. Post-operative data include pain, analgesic consumption, nausea and vomiting, as well as patients and surgeons satisfaction.

Inclusion Criteria:

• pregnant women with American Society of Anesthesiologist (ASA) 2-3
• scheduled for elective cesarean section.

Exclusion Criteria:

• refuse to participate in the study,
• requiring emergency obstetric care,
• ASA IV or V,
• having systemic diseases,
• a known fetal anomaly,
• placenta previa,
• abruption placenta
• with a history of hypersensitivity or allergy to any of the study drugs,
• operation time longer than 1.5 hour,
• blood loss more than 1500 millilitres,
• those with any contraindication to the technique proposed,