Reliability of cardiotocography in predicting baby's condition at birth.

Abstract

A prospective study of 6825 labours was undertaken to determine the relation between the Apgar scores of the babies at one minute and the cardiotocograph tracing in labour. The sensitivity of an abnormal tracing was 35.2% for babies who needed intermittent positive pressure ventilation and 20.0% for babies who did not but who had Apgar scores of less than 7. The sensitivity of an abnormal tracing for all babies with an Apgar score of less than 7 was 23.2%. The positive predictive value of an abnormal tracing was 8.7% for babies who needed intermittent positive pressure ventilation and 18.7% for babies who did not but who had an Apgar score of less than 7. The positive predictive value of an abnormal tracing was 27.4% for all babies with an Apgar score of less than 7. The specificity of the tracing was 93.4% for babies with an Apgar score of 7 or over. The relatively high incidence of false positive predictions might be explained on the grounds that abnormalities in the cardiotocograph tracing are a more sensitive indicator of hypoxia than the Apgar score. False negative predictions might have been due to adverse factors other than hypoxia--for example, fetal trauma, compression of the head, infection, and analgesia in labour. These findings suggest that the current overdependence on fetal monitoring by cardiotocography alone should be examined and that other reliable indicators for non-hypoxic fetal distress should be sought.