 Maternal hypotension is a common complication after spinal anesthesia for cesarean delivery CD. Many vasopressors have been used for prevention of post-spinal hypotension PSH during CD; however, the optimum protocol for prophylaxis is not established yet. Phenylephrine PE is a popular vasopressor used in obstetric anesthesia; however, its use is limited by its marked cardiac depressant nature. Norepinephrine NE is a potent vasopressor characterized by both α adrenergic agonistic activity in addition to a weak β adrenergic agonistic activity; thus, NE is considered a vasopressor with minimal cardiac depressant effect; these pharmacological properties would make NE an attractive alternative to PE. In this study, the investigators will compare continuous variable infusion of both drugs PE and NE with doses of 0.75 mcgKgmin and 0.1 mcgKgmin respectively for prophylaxis against PSH during CD. 