Fetal blood sampling in patients undergoing elective cesarean section: a correlation with cord blood gas values obtained at delivery.

Abstract

The purpose of this study was to compare blood gas parameters obtained after delivery and cord clamping with those obtained in the intact fetal circulation. Eighteen patients undergoing elective cesarean section at term were studied. Before the induction of epidural anesthesia, cordocentesis was performed under ultrasonographic guidance. Subsequently, a second sample was obtained for cord blood gas analysis after delivery. Umbilical venous blood was analyzed for pH, PO2, PCO2, and base excess. When comparing samples obtained from the intact fetal circulation with those obtained after delivery, there was a significant difference in pH (7.36 +/- 0.03 vs 7.31 +/- 0.04; p less than 0.0001), PCO2 (41.15 +/- 3.66 vs 46.29 +/- 5.71; p less than 0.018), PO2 (32.92 +/- 8.54 vs 26.97 +/- 4.43, p less than 0.02), and base excess (-0.79 +/- 1.19 vs -2.36 +/- 1.48; p less than 0.0003). These results should be considered when cord blood gas values obtained at delivery are correlated with those from the prenatal fetal state. Blood gas values obtained at delivery may not reflect the true prenatal fetal acid-base status.