Background: Fluid therapy in perioperative cesarean section remains a debated topic. Its purpose is to maintain or restore circulating blood volume and may affect the plasma acid-base balance of mother and neonatal. Therefore, the aim of this study was to compare the effects of Normal saline with Ringer's lactate serum on the acid-base status of mother and neonate in elective cesarean section. Methods: forty-eight healthy term parturient women scheduled for elective cesarean section were randomly divided into two groups (24 patients each). The first group received Normal saline serum and the second group received ringer lactate serum. Maternal blood samples were obtained from an indwelling cannula in a peripheral hand vein and Fetal arterial and venous blood samples were obtained at birth from a double-clamped umbilical cord. The data collected during the study included PH, PCO2, HCO3 and BE. At birth, 1- and 5-minute Apgar scores were recorded. Data were analyzed using descriptive statistics and inferential statistics at a significance level of less than 0.05. Results: Patients did not differ significantly in terms of demographic characteristics. The acidosis in mothers was higher in lactated ringer group (5%, p <0.001). There was no difference in Apgar score between the two groups. Conclusion: Normal saline compared to lactated ringer causes acidosis in mothers under elective cesarean section with spinal anesthesia, but none of them has a significant effect on the acid-base status of the infant. Appropriate fluid therapy aimed at optimization of pH can be effective for mothers who are at higher risk for acidosis.