Since 2011, phenylephrine was recommended as the preferred drug to maintain blood pressure in obstetric anesthesia.Phenylephrine, an α adrenoceptor agonist, can induce peripheral vasoconstriction to maintain blood pressure, while reflexly decrease heart rate and result in cardiac output (CO) reduction.Dyer et al. used bioimpedance technique to analyze the hemodynamic changes in normal pregnant women. A bolus of 80 ug phenylephrine was administrated when maternal mean arterial pressure decreased 20% after CSEA. It was found that cardiac output (CO) decreased significantly (14%) after phenylephrine administrationcompared with the baseline.And the decrease of CO induced by phenylephrine was in a dose dependent.All the studies referred above recruitednormal pregnant women, and the decreased CO did not have an adverse effect on neonatal birth. However, as we all know, the decrease of CO will influence uteroplacental blood, which may lead to adverse results in existed intrauterine distress fetal. All authors of those studies stressed that the decrease of CO induced by phenylephrine may increase the risks of fetal distress or other adverse consequences. So, it is crucial for obstetric anesthesiologist to choose a suitable vasoactive drugs, which can maintain both maternal blood pressure and uteroplacental perfusion in order to keep intrauterine environment steady.