Background Physiological changes associated with pregnancy are significant enough to have serious anesthetic implications. When these are compounded by obesity, the anesthesiologists may have to deal with a patient with seriously limited physiological reserve. Obese patients often had co-morbidities and pathological changes in different organ systems. Aim The objective of this study is to determine if obesity have a clinical important effect on the vasopressor requirements or the block height following a standard fixed dose of spinal anesthesia during elective cesarean delivery. Methodology In this prospective randomized comparative clinical study, two groups of 33 patients were recruited with widely differing body mass indices to examine the influence of body mass index (BMI) on the responses to a specific dose of spinal bupivacaine. One group includes women with BMI < 32 kg/m2 (group N) and the other group has a BMI of > 40 kg/m2 (group O). Results This study showed that Body Mass Index doesn’t have much influence on sensorimotor block level and vasopressor requirement during spinal anesthesia for elective cesarean delivery &so the dose of spinal bupivacaine should not be reduced in morbidly obese parturients. Conclusion The result of the present study showed that Body Mass Index up to 50 doesn’t have much influence on sensorimotor block level or vasopressor requirement during spinal anesthesia for elective cesarean delivery &so the dose of spinal bupivacaine should not be reduced in morbidly obese parturients.