The aetiology, characteristics and diagnostic relevance of late deceleration patterns in routine obstetric practice.

A retrospective study is described in which all the late deceleration patterns seen in one obstetric unit over the course of 34 months have been reviewed with regard to their apparent aetiology, their characteristics and associated abnormal fetal heart rate patterns and the incidence of fetal distress. The results show that, regardless of the aetiology and the characteristics, the incidence of fetal distress (defined as a pH of less than 7-25 or an Apgar score of less than 7 at one minute) lies between 40 and 50 per cent. The implications of this degree of diagnostic inaccuracy are discussed and the importance of fetal blood sampling as the final arbiter in the diagnosis is emphasized. During the course of the study a significant relationship was demonstrated between the use of epidural analgesia and the incidence of late deceleration patterns. This finding is discussed.