In this double-blind (Patient and nurse) clinical trial, 120 patients candidate for cesarean section will be randomly divided into two groups of intervention and control with table of random numbers and intrathecal and intravenous Dexamethasone are compared to reduce post operation complications after cesarean section. Spinal anesthesia will be provided in a sitting position with a spinal needle (25 Gauge) made by Dr.japanco company, China in the space between L3-L4 or L4-L5 with injection of 10 mg Marcaine 0.5% (10 mL in 2 cc) and 0.2 mg of intrathecal morphine made by Iran hormone Co. in both groups. The case group receives 8 mg intrathecal Dexamethasone injected in the same space (2 cc, made by Iran Hormone Co.) and the control group receives 8 mg lntravenous Dexamethasone made by Iran Hormone Co. in addition to 2 cc intratechal distilled water in the same vertebral space. The severity and incidence of nausea, vomiting, itching and pain will be recorded by an expert nurse or anesthesiology resident who are unaware of the study groups in recovery room and then at 1, 6, 12 and 24 hours after discharge from the recovery based on visual analog scale (VAS). If nausea and vomiting rate is higher than 4, 4 mg ondansetron made by Iran Hormone Co. will be prescribed and the injection will be recorded. Then, the patient’s satisfaction is asked based on VAS. Finally, BMI, age, education level, duration of surgery and anesthesia, history of nausea and vomiting after surgery and the amount of ondansetron used 24 hours after surgery will be recorded.