General anesthesia during pregnancy is associated with several major risks including unanticipated difficult airway, pulmonary aspiration, and specific anesthetic effects on the newborn. Thus, intrathecal anesthesia is the technique of choice for cesarean section. Nevertheless, the main side effect of intrathecal anesthesia is arterial hypotension which depend mainly on the dose of local anesthetic administered intrathecally. To date there is no guidelines nor evidences whic help the anesthetist to precisely estimate the required dose. Most often a standardized dose of 8 to 10 mg of bupivacaine is administered. However, some data suggest that a lower dose may be administered resulting in less frequent arterial hypotension. Nevertheless, a well designed randomized study is lacking.