THE ETIOLOGY OF FETAL ACIDOSIS AS DETERMINED BY UMBILICAL-CORD ACID-BASE STUDIES

OBJECTIVE: Our purpose was to determine whether umbilical cord acid-ba se values might be used to differentiate abruptio placentae from cord prolapse. STUDY DESIGN: By use of a retrospective study design, umbili cal 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-lest, Ma nn-Whitney U tests, and receiver-operator curve characteristic analyse s. RESULTS: No significant differences in electronic fetal heart rate record interpretations were detected. Highly significant differences i n umbilical arterial and umbilical venous blood gas values were noted between the two groups. Most notable were the differences between umbi lical 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 cutof f value in differentiating cord prolapse from abruptio placentae (accu racy 92%). CONCLUSION: Umbilical arterial blood gas values combined wi th umbilical venous blood gas values can assist in determining the pat hogenesis of marked fetal acidosis.