Twenty-four-hour CTG monitoring: comparison of normal pregnancies of 25-30 weeks of gestation versus 36-42 weeks of gestation.

Objective: Routinely antepartal cardiotocogram (CTG) is recorded for 30 min in order to obtain normal resting phases (<30 min) or a decrease of irregulatory due to hypoxia (>30 min) or to differentiate these from each other. In case of early onset of hypoxia first pathological findings might only be seen by chance in incidentally recorded CTG. The goal of this study was, if a continuous 24-h CTG allows an earlier detection of beginning hypoxia in case of normal pregnancies of 36-42 weeks compared to pregnancies of 25-30 weeks of gestation, and if there are any differences between both groups concerning the qualitative and quantitative description or the detection of a circadian rhythm.

Methods: 21 patients in each group had 24-h CTGs by means of telemetry (Hewlett-Packard type 78101A, 80110A). In both study groups, fetal heart-rate tracing included a full qualitative and quantitative description. Comparison of the results of both groups was done to look for early signs of pathological findings concerning reduced fetal well-being and a potential day and night rhythm.

Results: In comparison to 36-42 weeks of pregnancies 25-30 weeks had significantly more physiological undulatory oscillation and less narrowed undulatory oscillation (P < 0.001), as well as less resting phases (P < 0.001). Baseline tachycardia and bradycardia showed significantly increasing quantity (P < 0.001).

Conclusion: Twenty-four-hour CTG is a good screening method to detect early onset of hypoxia in case of second and third trimester pregnancies and a big help to detect a fetus at risk earlier. In future computerized CTG-systems should be proved in this connection and should be compared with our study.