Umbilical Cord Unmeasured Anions and Tissue Acid Levels According to Stewart’s Method in Term Newborn Infants and the Impact of Delivery Mode on these parameters

Aim: To determine the reference values of strong ion difference (SID), effective SID (SIDe), unmeasured anions (UMA), tissue acids (TA), lactate and Chloride-Sodium (Cl-Na) ratio of umbilical cord blood, and to evaluate the impact of delivery mode on these parameters. Methods: This prospective study was performed on healthy term newborn infants that had normal progress throughout the first and second stages of labor during normal spontaneous delivery (NSD) and cesarean section (C/S). Immediately after birth, 1ml and 2 ml of umbilical venous cord blood samples were obtained for blood gas analysis and blood chemistry respectively. The Cl-Na ratio, anion gap (AG), albumin corrected AG (AGCorr), SID, SIDe, UMA and TA were calculated in NSD and C/S groups.. Results: A total of 181 healthy newborn infants were included the study. Fifty-one infants were delivered by NSD and 130 infants by C/S. The pH and PCO2 values were similar in both groups. The mode of delivery had a significant impact on the umbilical cord AG, AGCorr, SID, lactate, UMA, and TA levels. All these values were significantly higher in NSD than C/S group. Conclusion: Umbilical cord blood gas analysis is a common practice to evaluate fetal status at delivery. The calculation of blood gas parameters in perinatal problems according to Stewart’s method may lead further understanding how perinatal conditions of the mother influence the fetus and newborn infant.