Background: The choice of anesthesia for caesarean section depends upon indication for operation, its urgency, patients and obstetrician preferences and skills of the anesthetist .Either of the general and spinal anesthesia is not ideal for caesarean section because each has advantages and risk to both mother and fetus. However the aim of the anesthetist is to choose the method which is safest and most comfortable for the mother, least depressant to the newborn and which provides optimal working conditions for the obstetrician.Objectives: to clarify the effect of volume preload or co?load is better in management of the change in blood pressure after parturition under spinal anesthesia for caesarean section. Materials and Methods: The study was carried out at Al?Sadr Teaching Hospital in Missan from January 2016 to January 2018. It was performed as comparative study on 60 healthy full term patients presented for elective lower segment caesarean section. They were divided into groups first one as thirty patients which were given crystalloid solution as preloading 15 minutes before induction. Second group as thirty patients which were given crystalloid solution as co?loading while induction of spinal anesthesia. Results: Out of 30 patients who administered preloading dose of crystalloid solution before induction of spinal anesthesia 23 patients were developed hypotension after spinal anesthesia. On the other hand out of 30 patients who administered co-loading of crystalloid solution with induction of spinal anesthesia 15 patients were developed hypotension. It had been found that those patients who were administered preloading were more likely to develop hypotension than those administered co-loading. Conclusions: There is significant difference between the effect of preloading and coloading on blood pressure after spinal anesthesia.