Can antepartum computerized cardiotocography predict the evolution of intrapartum acid-base status in normal fetuses?

Background: To study the relationship between antepartum computerized cardiotocography (cCTG) and the evolution of intrapartum fetal acid-base balance in a low-risk population.

Methods: Forty-nine healthy fetuses were prospectively followed up by antepartum cCTG (Oxford System 8002), fetal scalp blood sampling at the onset of the active phase of dilatation (3 cm) and at the beginning of the second stage of labor (10 cm) and study of acid-base status at birth in the umbilical cord. Correlation studies and linear regression analysis were performed.

Results: Normal prelabor cCTG was followed by normal fetal acid-base balance in the different study periods. No relationship was found between cCTG parameters and the absolute values of fetal acid-base status. However, the more favorable the antepartum cCTG parameters were, the more favorable the fetal acid-base evolution during the active phase of dilatation was. In contrast, no significant correlations were found between antepartum cCTG and fetal acid-base changes during the second stage of labor.

Conclusions: In normal fetuses, a single antepartum cCTG identified correctly fetal well-being during labor and at birth and was able to predict fetal acid-base evolution during the active phase of dilatation. However, fetal biochemical changes during the second stage could not be predicted by any antepartum cCTG parameter.