Inclusion Criteria:  Adult women admitted to Necker Enfants Malades hospital for scheduled cesarean section under spinal anesthesia Written informed consent  Exclusion Criteria:  No health insurance Urgent cesarean Failure of spinal anesthesia Free and informed consent impossible to obtain (especially due to a language barrier) Severe cardiovascular or neurovascular comorbidities Contraindication to the PLR (intracranial hypertension, fractures of the pelvis and / or lower limbs, ...) Background of preeclampsia or eclampsia Severe fetal pathology