The purpose of this study is comparison the effects of oxytocin and methylergonovine in caesarean section under spinal anesthesia. This study is designed as a randomized, prospective, interventional and single blind clinical trial. The study population is all the parturients who are candidate for elective caesarean section under spinal anesthesia. Inclusion criteria consist of: Elective caesarean section . Exclusion criteria consist of: Positive history of cardiovascular disease; Positive history of preeclampsia; Emergent caesarean section; Factors increasing risk of uterine atony . In this study 80 patients are selected and 40 patients in one groups are considered. One group of patients is received 0.2 mg methylergonovine in 1 liter isotonic serum infused after delivery of fetus . Another group of patients is received 30 unit oxytocin in 1 liter isotonic serum infused after delivery of fetus. All the patients after spinal anesthesia in supine position will be monitored and systolic blood pressure; diastolic blood pressure; heart rate and mean arterial blood pressure are recorded in minutes 1,3,5 after spinal anesthesia .Also systolic blood pressure; diastolic blood pressure; heart rate and mean arterial blood pressure are recorded in minutes 1,3,5,10,15,20 after drug administration. Amount of bleeding are estimated by volume of bottle of suctioning apparatus and field of surgery. Hemodynamic parameters are recorded in minutes 5,10,15,20,30 in recovery room.