Background: cesarean section is the surgical delivery of a baby that involves making an incision in the mother's abdominal wall and uterus. Spinal anesthesia is considered the “gold standard" technique for cesarean section. Hypotension is the most common side effect of neuraxial blocks in the obstetric patient with an incidence rate reported as high as 83%. This has remained a significant concern for the anesthesiologist during management of this patient. Aim of the work: This study will be performed to compare the effects of colloid pre-load and colloid co-load on maternal haemodynamic changes during spinal anaesthesia for cesarean section. Patient's and Methods: A comparative cross sectional study was conducted at Ain Shams Maternity Hospital. After obtaining approval of research ethical committee and patients' informed consents at which 105 women with full term singleton pregnancies were scheduled for elective cesarean section and received spinal anesthesia. The patient's age were between 18 -42 years, of ASA physical status. In our study 3 groups of patients were compared; each group is formed of 35 patients Group 1;  patients were  pre-loaded with 500 ml of 6% HES(hydroxyethyl starch 130/0.4) 20 minutes before induction of anesthesia. Group2; patients were co-loaded with 500ml of 6% HES (hydroxyethyl starch 130/0.4) during injection of bupivacaine. Group 3; patients were pre-loaded with 500ml lactated ringer solution 20 minutes before induction of anaesthesia. Results: There was a decrease in SBP, DBP,MAP and HR in the 3 groups where the lowest values were recorded in group 3 between 6-15 minutes and there was a high statistical difference p˂0.0001 while the intergroup comparison of the groups 1 and 2 showed no statistical significance as regards SBP,DBP,MAP and HR. Conclusion: In this study it was found that colloid co-load was somewhat how equal to colloid pre-load in prevention of hypotension in a parturient undergoing cesarean section under spinal anesthesia in addition it was found that crystalloid pre-load was inferior to colloid co-load or pre-load in maintaining blood pressure during spinal anesthesia in parturients .