The etiology of fetal acidosis as determined by umbilical cord acid- base studies

OBJECTIVE: Our purpose was to determine whether umbilical cord acid- base values might be used to differentiate abruptio placentae from cord prolapse. STUDY DESIGN: By use of a retrospective study design, umbilical cord blood acid-base values of 32 cases of severely acidotic acute abruptio placentae were statistically compared with those of 19 cases of severely acidotic acute cord prolapse with Fisher's exact test, Mann-Whitney U tests, and receiver-operator curve characteristic analyses. RESULTS: No significant differences in electronic fetal heart rate record interpretations were detected. Highly significant differences in umbilical arterial and umbilical venous blood gas values were noted between the two groups. Most notable were the differences between umbilical venous and arterial blood gas values in the cord prolapse group. Receiver-operator characteristic curve analysis demonstrated that an umbilical venous-arterial pH difference of 0.15 was an effective cutoff value in differentiating cord prolapse from abruptio placentae (accuracy 92%). CONCLUSION: Umbilical arterial blood gas values combined with umbilical venous blood gas values can assist in determining the pathogenesis of marked fetal acidosis.