Computerised analysis of fetal heart rate recordings in maternal type I diabetes mellitus

Abstract

Objective 1. To study computerised cardiotocograph parameters from women with type I diabetes; 2. to examine the significance of observed differences from the expected normal values. Design Prospective observational study in the third trimester of pregnancy. Setting The medical antenatal clinic of a tertiary referral centre. Population Twenty-six women with type I diabetes mellitus with a singleton pregnancy. Methods Computerised cardiotocograph recordings were made weekly from 28 to 39 weeks. Derived parameters were compared with the published figures for uncomplicated singleton pregnancies. Details of maternal blood sugar, labour and delivery and neonatal outcome were recorded. Data were compared between groups according to the computerised analysis of the antenatal CTGs. Results One-hundred and thirty-one recordings were made with a median of five per patient (range 1–12). 11.3% showed absent episodes of high variation compared with the expected value of 0.8%, a difference of 9.5% (95% CI 4.5-15.3). Differences in short term variation, basal heart rate, frequency of fetal movements and heart rate accelerations were also found which changed with gestation. Overall these changes represented a more immature form of fetal heart rate than that which would be expected. No relationship between the changes and adverse fetal outcome could be identified. Conclusions Significant differences exist in cardiotocographs in maternal type I diabetes compared with normal fetuses. The changes may represent a delay in fetal maturation. The analysis mode of the computer will register these as abnormal features, but there is no evidence that they are pathological. We would recommend that computerised analysis is not used to assess pregnancies complicated by maternal type I diabetes mellitus.